Copyright © 2007-2010 Hans Dockter, Adam Murdoch
Table of Contents
List of Examples
We would like to introduce Gradle to you, a build system that we think is a quantum leap for build technology in the Java (JVM) world. Gradle provides:
A very flexible general purpose build tool like Ant.
Switchable, build-by-convention frameworks a la Maven. But we never lock you in!
Very powerful support for multi-project builds.
Very powerful dependency management (based on Apache Ivy).
Full support for your existing Maven or Ivy repository infrastructure.
Support for transitive dependency management without the need for remote repositories or
pom.xml
and ivy.xml
files.
Ant tasks and builds as first class citizens.
Groovy build scripts.
A rich domain model for describing your build.
In Chapter 2, Overview you will find a detailed overview of Gradle. Otherwise, the tutorials are waiting, have fun :)
This user guide, like Gradle itself, is under very active development. Some parts of Gradle aren't documented as completely as they need to be. Some of the content presented won't be entirely clear or will assume that you know more about Gradle than you do. We need your help to improve this user guide. You can find out more about contributing to the documentation at the Gradle web site.
You can find more examples, and some additions to this user guide, on the wiki. You can also contribute your own examples and extra content there.
Here is a list of some of Gradle's features.
At the heart of Gradle lies a rich extensible Domain Specific Language (DSL) based on Groovy. Gradle pushes declarative builds to the next level by providing declarative language elements that you can assemble as you like. Those elements also provide build-by-convention support for Java, Groovy, OSGi, Web and Scala projects. Even more, this declarative language is extensible. Add your own new language elements or enhance the existing ones. Thus providing concise, maintainable and comprehensible builds.
The declarative language lies on top of a general purpose task graph, which you can fully leverage in your builds. It provides utmost flexibility to adapt Gradle to your unique needs.
The suppleness and richness of Gradle finally allows you to apply common design principles to your build. For example, it is very easy to compose your build from reusable pieces of build logic. Inline stuff where unnecessary indirections would be inappropriate. Don't be forced to tear apart what belongs together (e.g. in your project hierarchy). Thus avoiding smells like shotgun changes or divergent change that turn your build into a maintenance nightmare. At last you can create a well structured, easily maintained, comprehensible build.
From being a pleasure to be used embedded to its many hooks over the whole lifecycle of build execution, Gradle allows you to monitor and customize its configuration and execution behavior to its very core.
Gradle scales very well. It significantly increases your productivity, from simple single project builds up to huge enterprise multi-project builds. This is true for structuring the build. With the state-of-art incremental build function, this is also true for tackling the performance pain many large enterprise builds suffer from.
Gradle's support for multi-project build is outstanding. Project dependencies are first class citizens. We allow you to model the project relationships in a multi-project build as they really are for your problem domain. Gradle follows your layout not vice versa.
Gradle provides partial builds. If you build a single subproject Gradle takes care of building all the subprojects that subproject depends on. You can also choose to rebuild the subprojects that depend on a particular subproject. Together with incremental builds this is a big time saver for larger builds.
Different teams prefer different ways to manage their external dependencies. Gradle provides convenient support for any strategy. From transitive dependency management with remote maven and ivy repositories to jars or dirs on the local file system.
Ant tasks are first class citizens. Even more interesting, Ant projects are first class citizens as well. Gradle provides a deep import for any Ant project, turning Ant targets into native Gradle tasks at runtime. You can depend on them from Gradle, you can enhance them from Gradle, you can even declare dependencies on Gradle tasks in your build.xml. The same integration is provided for properties, paths, etc ...
Gradle fully supports your existing Maven or Ivy repository infrastructure for publishing and retrieving dependencies. Gradle also provides a converter for turning a Maven pom.xml into a Gradle script. Runtime imports of Maven projects will come soon.
Gradle can adapt to any structure you have. Therefore you can always develop your Gradle build in the same branch where your production build lives and both can evolve in parallel. We usually recommend to write tests that make sure that the produced artifacts are similar. That way migration is as less disruptive and as reliable as possible. This is following the best-practices for refactoring by applying baby steps.
Gradle's build scripts are written in Groovy, not XML. But unlike other approaches this is not for simply exposing the raw scripting power of a dynamic language. That would just lead to a very difficult to maintain build. The whole design of Gradle is oriented towards being used as a language, not as a rigid framework. And Groovy is our glue that allows you to tell your individual story with the abstractions Gradle (or you) provide. Gradle provides some standard stories but they are not privileged in any form. This is for us a major distinguishing features compared to other declarative build systems. Our Groovy support is also not just some simple coating sugar layer. The whole Gradle API is fully groovynized. Only by that using Groovy is the fun and productivity gain it can be.
The Gradle Wrapper allows you to execute Gradle builds on machines where Gradle is not installed. This is useful for example for some continuous integration servers. It is also useful for an open source project to keep the barrier low for building it. The wrapper is also very interesting for the enterprise. It is a zero administration approach for the client machines. It also enforces the usage of a particular Gradle version thus minimizing support issues.
Gradle is an open source project, and is licensed under the ASL.
We think the advantages of an internal DSL (based on a dynamic language) over XML are tremendous in case of build scripts. There are a couple of dynamic languages out there. Why Groovy? The answer lies in the context Gradle is operating in. Although Gradle is a general purpose build tool at its core, its main focus are Java projects. In such projects obviously the team members know Java. We think a build should be as transparent as possible to all team members.
You might argue why not using Java then as the language for build scripts. We think this is a valid question. It would have the highest transparency for your team and the lowest learning curve. But due to limitations of Java such a build language would not be as nice, expressive and powerful as it could be. [1] Languages like Python, Groovy or Ruby do a much better job here. We have chosen Groovy as it offers by far the greatest transparency for Java people. Its base syntax is the same as Java's as well as its type system, its package structure and other things. Groovy builds a lot on top of that. But on a common ground with Java.
For Java teams which share also Python or Ruby knowledge or are happy to learn it, the above arguments don't apply. The Gradle design is well-suited for creating another build script engine in JRuby or Jython. It just doesn't have the highest priority for us at the moment. We happily support any community effort to create additional build script engines.
[1] At http://www.defmacro.org/ramblings/lisp.html you find an interesting article comparing Ant, XML, Java and Lisp. It's funny that the 'if Java had that syntax' syntax in this article is actually the Groovy syntax.
The following tutorials introduce some of the basics of Gradle, to help you get started.
Describes how to install Gradle.
Introduces the basic build script elements: projects and tasks.
Shows how to start using Gradle's build-by-convention support for Java projects.
Using Gradle's build-by-convention support for Groovy projects.
Using Gradle's build-by-convention support for Web applications.
Gradle requires a Java JDK to be installed. Gradle requires a JDK 1.5 or higher. Gradle ships with its own Groovy library, therefore no Groovy needs to be installed. Any existing Groovy installation is ignored by Gradle.
Gradle uses whichever JDK it finds in your path (to check, use java -version
).
Alternatively, you can set the JAVA_HOME
environment variable to point to the install directory
of the desired JDK.
You can download one of the Gradle distributions from the Gradle web site.
The Gradle distribution comes packaged as a ZIP. The full distribution contains:
The Gradle binaries.
The user guide (HTML and PDF).
The DSL reference guide.
The API documentation (Javadoc and Groovydoc).
Extensive samples, including the examples referenced in the user guide, along with some complete and more complex builds you can use the starting point for your own build.
The binary sources. This is for reference only. If you want to build Gradle you need to download the source distribution or checkout the sources from the source repository. See the Gradle web site for details).
You need a GNU compatible tool to unzip Gradle, if you want the file permissions to be properly set. We mention this as some zip front ends for Mac OS X don't restore the file permissions properly.
For running Gradle, add
to your GRADLE_HOME
/binPATH
environment variable. Usually, this is sufficient to run Gradle.
You run Gradle via the gradle command. To check if Gradle is properly installed just type gradle -v and you should get an output like:
------------------------------------------------------------ Gradle 1.0-milestone-2 ------------------------------------------------------------ Gradle build time: Thursday, 7 April 2011 04:24:33 PM EST Groovy: 1.7.10 Ant: Apache Ant(TM) version 1.8.2 compiled on December 20 2010 Ivy: 2.2.0 JVM: 1.6.0_22 (Sun Microsystems Inc. 17.1-b03) OS: Linux 2.6.35-23-generic amd64
JVM options for running Gradle can be set via environment variables. You can use GRADLE_OPTS
or JAVA_OPTS
. Those variables can be used together. JAVA_OPTS
is by convention an environment
variable shared by many Java applications. A typical use case would be to set the HTTP proxy in JAVA_OPTS
and the memory options in GRADLE_OPTS
. Those variables can also be set at the beginning
of the gradle or gradlew script.
Everything in Gradle sits on top of two basic concepts: projects and tasks.
Every Gradle build is made up of one or more projects. A project represents some component of your software which can be built. What this means exactly depends on what it is that you are building. For example, a project might represent a library JAR or a web application. It might represent a distribution ZIP assembled from the JARs produced by other projects. A project does not necessarily represent a thing to be built. It might represent a thing to be done, such as deploying your application to staging or production environments. Don't worry if this seems a little vague for now. Gradle's build-by-convention support adds a more concrete definition for what a project is.
Each project is made up of one or more tasks. A task represents some atomic piece of work which a build performs. This might be compiling some classes, creating a JAR, generating javadoc, or publishing some archives to a repository.
For now, we will look at defining some simple tasks in a build with one project. Later chapters will look at working with multiple projects and more about working with projects and tasks.
You run a Gradle build using the gradle command. The gradle command
looks for a file called build.gradle
in the current directory.
[2]
We call this build.gradle
file a build script, although strictly speaking it is
a build configuration script, as we will see later. The build script defines a project and its tasks.
To try this out, create the following build script named build.gradle
.
In a command-line shell, enter into the containing directory and execute the build script by running
gradle -q hello
:
-q
do?Most of the examples in this user guide are run with the -q
command-line option.
This suppresses Gradle's log messages, so that only the output of the tasks is shown. This keeps the example
output in this user guide a little clearer. You don't need to use this option if you don't want.
See Chapter 16, Logging for more details about the command-line options which affect Gradle's output.
What's going on here? This build script defines a single task, called hello
, and
adds an action to it. When you run gradle hello
, Gradle executes the
hello
task, which in turn executes the action you've provided. The action is simply a
closure containing some Groovy code to execute.
If you think this looks similar to Ant's targets, well, you are right. Gradle tasks are the equivalent to
Ant targets. But as you will see, they are much more powerful. We have used a different terminology than Ant
as we think the word task is more expressive than the word target.
Unfortunately this introduces a terminology clash with Ant, as Ant calls its commands, such as
javac
or copy
, tasks. So when we talk about tasks,
we always mean Gradle tasks, which are the equivalent to Ant's targets. If we talk
about Ant tasks (Ant commands), we explicitly say ant task.
There is a shorthand way to define a task like our hello
task above, which is more
concise.
Again, this defines a task called hello
with a single closure to execute.
We will use this task definition style throughout the user guide.
Gradle's build scripts expose to you the full power of Groovy. As an appetizer, have a look at this:
Example 5.4. Using Groovy in Gradle's tasks
build.gradle
task upper << { String someString = 'mY_nAmE' println "Original: " + someString println "Upper case: " + someString.toUpperCase() }
Output of gradle -q upper
> gradle -q upper Original: mY_nAmE Upper case: MY_NAME
or
Example 5.5. Using Groovy in Gradle's tasks
build.gradle
task count << {
4.times { print "$it " }
}
Output of gradle -q count
> gradle -q count 0 1 2 3
As you probably have guessed, you can declare dependencies between your tasks.
Example 5.6. Declaration of dependencies between tasks
build.gradle
task hello << { println 'Hello world!' } task intro(dependsOn: hello) << { println "I'm Gradle" }
Output of gradle -q intro
> gradle -q intro Hello world! I'm Gradle
To add a dependency, the corresponding task does not need to exist.
Example 5.7. Lazy dependsOn - the other task does not exist (yet)
build.gradle
task taskX(dependsOn: 'taskY') << { println 'taskX' } task taskY << { println 'taskY' }
Output of gradle -q taskX
> gradle -q taskX taskY taskX
The dependency of taskX
to taskY
is declared before
taskY
is defined. This is very important for multi-project builds. Task dependencies are
discussed in more detail in Section 14.4, “Adding dependencies to a task”.
Please notice, that you can't use a shortcut notation (see Section 5.8, “Shortcut notations”) when referring to task, which is not defined yet.
The power of Groovy can be used for more than defining what a task does. For example, you can also use it to dynamically create tasks.
Example 5.8. Dynamic creation of a task
build.gradle
4.times { counter -> task "task$counter" << { println "I'm task number $counter" } }
Output of gradle -q task1
> gradle -q task1 I'm task number 1
Once tasks are created they can be accessed via an API. This is different to Ant. For example you can create additional dependencies.
Example 5.9. Accessing a task via API - adding a dependency
build.gradle
4.times { counter -> task "task$counter" << { println "I'm task number $counter" } } task0.dependsOn task2, task3
Output of gradle -q task0
> gradle -q task0 I'm task number 2 I'm task number 3 I'm task number 0
Or you can add behavior to an existing task.
Example 5.10. Accessing a task via API - adding behaviour
build.gradle
task hello << { println 'Hello Earth' } hello.doFirst { println 'Hello Venus' } hello.doLast { println 'Hello Mars' } hello << { println 'Hello Jupiter' }
Output of gradle -q hello
> gradle -q hello Hello Venus Hello Earth Hello Mars Hello Jupiter
The calls doFirst
and doLast
can be executed multiple times.
They add an action to the beginning or the end of the task's actions list. When the task executes, the
actions in the action list are executed in order. The <<
operator is simply an
alias for doLast
.
As you might have noticed in the previous examples, there is a convenient notation for accessing an existing task. Each task is available as a property of the build script:
Example 5.11. Accessing task as a property of the build script
build.gradle
task hello << { println 'Hello world!' } hello.doLast { println "Greetings from the $hello.name task." }
Output of gradle -q hello
> gradle -q hello Hello world! Greetings from the hello task.
This enables very readable code, especially when using the out of the box tasks provided by the plugins
(e.g. compile
).
You can assign arbitrary new properties to any task.
Example 5.12. Assigning properties to a task
build.gradle
task myTask
myTask.myProperty = 'myCustomPropValue'
task showProps << {
println myTask.myProperty
}
Output of gradle -q showProps
> gradle -q showProps myCustomPropValue
Ant tasks are first-class citizens in Gradle. Gradle provides excellent integration for Ant tasks simply
by relying on Groovy. Groovy is shipped with the fantastic AntBuilder
. Using Ant tasks
from Gradle is as convenient and more powerful than using Ant tasks from a build.xml
file. From below example you can learn how to execute ant tasks and how to access ant properties:
Example 5.13. Using AntBuilder to execute ant.loadfile target
build.gradle
task loadfile << { def files = file('../antLoadfileResources').listFiles().sort() files.each { File file -> if (file.isFile()) { ant.loadfile(srcFile: file, property: file.name) println " *** $file.name ***" println "${ant.properties[file.name]}" } } }
Output of gradle -q loadfile
> gradle -q loadfile *** agile.manifesto.txt *** Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan *** gradle.manifesto.txt *** Make the impossible possible, make the possible easy and make the easy elegant. (inspired by Moshe Feldenkrais)
There is lots more you can do with Ant in your build scripts. You can find out more in Chapter 17, Using Ant from Gradle.
Gradle scales in how you can organize your build logic. The first level of organizing your build logic for the example above, is extracting a method.
Example 5.14. Using methods to organize your build logic
build.gradle
task checksum << { fileList('../antLoadfileResources').each {File file -> ant.checksum(file: file, property: "cs_$file.name") println "$file.name Checksum: ${ant.properties["cs_$file.name"]}" } } task loadfile << { fileList('../antLoadfileResources').each {File file -> ant.loadfile(srcFile: file, property: file.name) println "I'm fond of $file.name" } } File[] fileList(String dir) { file(dir).listFiles({file -> file.isFile() } as FileFilter).sort() }
Output of gradle -q loadfile
> gradle -q loadfile I'm fond of agile.manifesto.txt I'm fond of gradle.manifesto.txt
Later you will see that such methods can be shared among subprojects in multi-project builds. If your build logic becomes more complex, Gradle offers you other very convenient ways to organize it. We have devoted a whole chapter to this. See Chapter 41, Organizing Build Logic.
Gradle allows you to define one or more default tasks for your build.
Example 5.15. Defining a default tasks
build.gradle
defaultTasks 'clean', 'run' task clean << { println 'Default Cleaning!' } task run << { println 'Default Running!' } task other << { println "I'm not a default task!" }
Output of gradle -q
> gradle -q Default Cleaning! Default Running!
This is equivalent to running gradle clean run
. In a multi-project build every
subproject can have its own specific default tasks. If a subproject does not specify default tasks, the
default tasks of the parent project are used (if defined).
As we describe in full detail later (See Chapter 37, The Build Lifecycle) Gradle has a configuration phase and an execution phase. After the configuration phase Gradle knows all tasks that should be executed. Gradle offers you a hook to make use of this information. A use-case for this would be to check if the release task is part of the tasks to be executed. Depending on this you can assign different values to some variables.
In the following example, execution of distribution
and release
tasks results in different value of version
variable.
Example 5.16. Different outcomes of build depending on chosen tasks
build.gradle
gradle.taskGraph.whenReady {taskGraph -> if (taskGraph.hasTask(':release')) { version = '1.0' } else { version = '1.0-SNAPSHOT' } } task distribution << { println "We build the zip with version=$version" } task release(dependsOn: 'distribution') << { println 'We release now' }
Output of gradle -q distribution
> gradle -q distribution We build the zip with version=1.0-SNAPSHOT
Output of gradle -q release
> gradle -q release We build the zip with version=1.0 We release now
The important thing is, that the fact that the release task has been chosen, has an effect before the release task gets executed. Nor has the release task to be the primary task (i.e. the task passed to the gradle command).
This is not the end of the story for tasks. So far we have worked with simple tasks. Tasks will be revisited in Chapter 14, More about Tasks and when we look at the Java plugin in Chapter 20, The Java Plugin.
As we have seen, Gradle is a general-purpose build tool. It can build pretty much anything you care to implement in your build script. Out-of-the-box, however, it doesn't build anything unless you add code to your build script to do so.
Most Java projects are pretty similar as far as the basics go: you need to compile your Java source files, run some unit tests, and create a JAR file containing your classes. It would be nice if you didn't have to code all this up for every project. Luckily, you don't have to. Gradle solves this problem through the use of plugins. A plugin is an extension to Gradle which configures your project in some way, typically by adding some pre-configured tasks which together do something useful. Gradle ships with a number of plugins, and you can easily write your own and share them with others. One such plugin is the Java plugin. This plugin adds some tasks to your project which will compile and unit test your Java source code, and bundle it into a JAR file.
The Java plugin is convention based. This means that the plugin defines default values for many aspects of the project, such as where the Java source files are located. If you follow the convention in your project, you generally don't need to do much in your build script to get a useful build. Gradle allows you to customize your project if you don't want to or cannot follow the convention in some way. In fact, because support for Java projects is implemented as a plugin, you don't have to use the plugin at all to build a Java project, if you don't want to.
We have in-depth coverage with many examples about the Java plugin, dependency management and multi-project builds in later chapters. In this chapter we want to give you an initial idea of how to use the Java plugin to build a Java project.
Let's look at a simple example. To use the Java plugin, add the following to your build file:
Example 6.1. Using the Java plugin
build.gradle
apply plugin: 'java'
Note: The code for this example can be found at samples/java/quickstart
which is in both the binary and source distributions of Gradle.
This is all you need to define a Java project. This will apply the Java plugin to your project, which adds a number of tasks to your project.
You can use gradle tasks
to list the tasks of a project. This will let you see
the tasks that the Java plugin has added to your project.
Gradle expects to find your production source code under src/main/java
and your test
source code under src/test/java
. In addition, any files under
src/main/resources
will be included in the JAR file as resources, and any files under
src/test/resources
will be included in the classpath used to run the tests. All output
files are created under the build
directory, with the JAR file ending up in the
build/libs
directory.
The Java plugin adds quite a few tasks to your project. However, there are only a handful of tasks
that you will need to use to build the project. The most commonly used task is the build
task,
which does a full build of the project. When you run gradle build
, Gradle will
compile and test your code, and create a JAR file containing your main classes and resources:
Example 6.2. Building a Java project
Output of gradle build
> gradle build :compileJava :processResources :classes :jar :assemble :compileTestJava :processTestResources :testClasses :test :check :build BUILD SUCCESSFUL Total time: 1 secs
Some other useful tasks are:
Deletes the build
directory, removing all built files.
Compiles and jars your code, but does not run the unit tests. Other plugins add more artifacts to this task. For example, if you use the War plugin, this task will also build the WAR file for your project.
Compiles and tests your code. Other plugins add more checks to this task. For example, if you use the Code-quality plugin, this task will also run Checkstyle against your source code.
Usually, a Java project will have some dependencies on external JAR files. To reference these JAR files in the project, you need to tell Gradle where to find them. In Gradle, artifacts such as JAR files, are located in a repository. A repository can be used for fetching the dependencies of a project, or for publishing the artifacts of a project, or both. For this example, we will use the public Maven repository:
Let's add some dependencies. Here, we will declare that our production classes have a compile-time dependency on commons collections, and that our test classes have a compile-time dependency on junit:
Example 6.4. Adding dependencies
build.gradle
dependencies { compile group: 'commons-collections', name: 'commons-collections', version: '3.2' testCompile group: 'junit', name: 'junit', version: '4.+' }
You can find out more in Chapter 34, Dependency Management.
The Java plugin adds a number of properties to your project. These properties have default values which are usually sufficient to get started. It's easy to change these values if they don't suit. Let's look at this for our sample. Here we will specify the version number for our Java project, along with the Java version our source is written in. We also add some attributes to the JAR manifest.
Example 6.5. Customization of MANIFEST.MF
build.gradle
sourceCompatibility = 1.5 version = '1.0' jar { manifest { attributes 'Implementation-Title': 'Gradle Quickstart', 'Implementation-Version': version } }
You can use gradle properties
to list the properties of a project. This will allow
you to see the properties added by the Java plugin, and their default values.
The tasks which the Java plugin adds are regular tasks, exactly the same as if they were declared in
the build file. This means you can use any of the mechanisms shown in earlier chapters to customise
these tasks. For example, you can set the properties of a task, add behaviour to a task, change the
dependencies of a task, or replace a task entirely. In our sample, we will configure the
test
task, which is of type Test
, to
add a system property when the tests are executed:
Usually the JAR file needs to be published somewhere. To do this, you need to tell Gradle where to publish the JAR file. In Gradle, artifacts such as JAR files are published to repositories. In our sample, we will publish to a local directory. You can also publish to a remote location, or multiple locations.
Example 6.7. Publishing the JAR file
build.gradle
uploadArchives {
repositories {
flatDir(dirs: file('repos'))
}
}
To publish the JAR file, run gradle uploadArchives
.
To import your project into Eclipse, you need to add another plugin to your build file:
Now execute gradle eclipse
command to generate Eclipse project files. More on Eclipse
task can be found in Chapter 28, The Eclipse Plugin.
Here's the complete build file for our sample:
Example 6.9. Java example - complete build file
build.gradle
apply plugin: 'java' apply plugin: 'eclipse' sourceCompatibility = 1.5 version = '1.0' jar { manifest { attributes 'Implementation-Title': 'Gradle Quickstart', 'Implementation-Version': version } } repositories { mavenCentral() } dependencies { compile group: 'commons-collections', name: 'commons-collections', version: '3.2' testCompile group: 'junit', name: 'junit', version: '4.+' } test { systemProperties 'property': 'value' } uploadArchives { repositories { flatDir(dirs: file('repos')) } }
Now let's look at a typical multi-project build. Below is the layout for the project:
Example 6.10. Multi-project build - hierarchical layout
Build layout
multiproject/ api/ services/webservice/ shared/
Note: The code for this example can be found at samples/java/multiproject
which is in both the binary and source distributions of Gradle.
Here we have three projects. Project api
produces a JAR file which is shipped to the
client to provide them a Java client for your XML webservice. Project webservice
is a
webapp which returns XML. Project shared
contains code used both by api
and webservice
.
To define a multi-project build, you need to create a settings file. The settings
file lives in the root directory of the source tree, and specifies which projects to include in the
build. It must be called settings.gradle
. For this example, we are using a simple
hierarchical layout. Here is the corresponding settings file:
Example 6.11. Multi-project build - settings.gradle file
settings.gradle
include "shared", "api", "services:webservice", "services:shared"
You can find out more about the settings file in Chapter 38, Multi-project Builds.
For most multi-project builds, there is some configuration which is common to all projects.
In our sample, we will define this common configuration in the root project, using a technique called
configuration injection. Here, the root project is like a container and the
subprojects
method iterates over the elements of this container - the projects in
this instance - and injects the specified configuration. This way we can easily define the manifest
content for all archives, and some common dependencies:
Example 6.12. Multi-project build - common configuration
build.gradle
subprojects { apply plugin: 'java' apply plugin: 'eclipse' repositories { mavenCentral() } dependencies { testCompile 'junit:junit:4.8.2' } version = '1.0' jar { manifest.attributes provider: 'gradle' } }
Notice that our sample applies the Java plugin to each subproject. This means the tasks and
configuration properties we have seen in the previous section are available in each subproject.
So, you can compile, test, and JAR all the projects by running gradle build
from
the root project directory.
You can add dependencies between projects in the same build, so that, for example, the JAR file of one
project is used to compile another project. In the api
build file we will add a dependency
on the JAR produced by the shared
project. Due to this dependency, Gradle will
ensure that project shared
always gets built before project api
.
Example 6.13. Multi-project build - dependencies between projects
api/build.gradle
dependencies {
compile project(':shared')
}
In this chapter, you have seen how to do some of the things you commonly need to build a Java based project. This chapter is not exhaustive, and there are many other things you can do with Java projects in Gradle. These are dealt with in later chapters. Also, a lot of the behaviour you have seen in this chapter is configurable. For example, you can change where Gradle looks Java source files, or add extra tasks, or you can change what any task actually does. Again, you will see how this works in later chapters.
You can find out more about the Java plugin in Chapter 20, The Java Plugin, and you can find more sample
Java projects in the samples/java
directory in the Gradle distribution.
To build a Groovy project, you use the Groovy plugin. This plugin extends the Java plugin to add Groovy compilation capabilties to your project. Your project can contain Groovy source code, Java source code, or a mix of the two. In every other respect, a Groovy project is identical to a Java project, which we have already seen in Chapter 6, Java Quickstart.
Let's look at an example. To use the Groovy plugin, add the following to your build file:
Example 7.1. Groovy plugin
build.gradle
apply plugin: 'groovy'
Note: The code for this example can be found at samples/groovy/quickstart
which is in both the binary and source distributions of Gradle.
This will also apply the Java plugin to the project, if it has not already been applied. The Groovy plugin
extends the compile
task to look for source files in directory
src/main/groovy
, and the compileTest
task to look for test source
files in directorysrc/test/groovy
. The compile tasks use joint compilation for these
directories, which means they can contain a mixture of java and groovy source files.
To use the groovy compilation tasks, you must also declare the Groovy version to use and where to find the
Groovy libraries. You do this by adding a dependency to the groovy
configuration.
The compile
configuration inherits this dependency, so the groovy libraries will
be included in classpath when compiling Groovy and Java source. For our sample, we will use Groovy 1.6.0
from the public Maven repository:
Example 7.2. Dependency on Groovy 1.6.0
build.gradle
repositories { mavenCentral() } dependencies { groovy group: 'org.codehaus.groovy', name: 'groovy', version: '1.7.10' }
Here is our complete build file:
Example 7.3. Groovy example - complete build file
build.gradle
apply plugin: 'eclipse' apply plugin: 'groovy' repositories { mavenCentral() } dependencies { groovy group: 'org.codehaus.groovy', name: 'groovy', version: '1.7.10' testCompile group: 'junit', name: 'junit', version: '4.8.2' }
Running gradle build
will compile, test and JAR your project.
This chapter describes a very simple Groovy project. Usually, a real project will require more than this. Because a Groovy project is a Java project, whatever you can do with a Java project, you can also do with a Groovy project.
You can find out more about the Groovy plugin in Chapter 21, The Groovy Plugin, and you can find more
sample Groovy projects in the samples/groovy
directory in the Gradle distribution.
This chapter is a work in progress.
This chapter introduces some of the Gradle's support for web applications. Gradle provides two plugins for web application developement: the War plugin and the Jetty plugin. The War plugin extends the Java plugin to build a WAR file for your project. The Jetty plugin extends the War plugin to allow you to deploy your web application to an embedded Jetty web container.
To build a WAR file, you apply the War plugin to your project:
Example 8.1. War plugin
build.gradle
apply plugin: 'war'
Note: The code for this example can be found at samples/webApplication/quickstart
which is in both the binary and source distributions of Gradle.
This also applies the Java plugin to your project. Running gradle build
will compile,
test and WAR your project. Gradle will look for the source files to include in the WAR file in
src/main/webapp
. Your compiled classes, and their runtime dependencies are also
included in the WAR file.
You can combine multiple plugins in a single project, so you can use the War and Groovy plugins together to build a Groovy based web application. The appropriate groovy libraries will be added to the WAR file for you.
To run your web application, you apply the Jetty plugin to your project:
This also applies the War plugin to your project. Running gradle jettyRun
will
run your web application in an embedded Jetty web container. Running gradle jettyRunWar
will build the WAR file, and then run it in an embedded web container.
TODO: which url, configure port, uses source files in place and can edit your files and reload.
You can find out more about the War plugin in Chapter 23, The War Plugin and the Jetty plugin in
Chapter 24, The Jetty Plugin. You can find more sample Java projects in the
samples/webApplication
directory in the Gradle distribution.
This chapter is currently under construction.
For all the details of artifact handling see Chapter 35, Artifact Management.
This chapter introduces some of the basics of artifact handling in Gradle.
Artifacts are grouped into configurations. A configuration is simply a set of files with a name. You can use them to declare the external dependencies your project has, or to declare the artifacts which your project publishes.
To define a configuration:
To access a configuration:
Example 9.2. Accessing a configuration
build.gradle
println configurations.compile.name
println configurations['compile'].name
To configure a configuration:
Example 9.3. Configuration of a configuration
build.gradle
configurations { compile { description = 'compile classpath' transitive = true } runtime { extendsFrom compile } } configurations.compile { description = 'compile classpath' }
Artifacts are stored in repositories.
To use maven central repository:
To use a local directory:
Example 9.5. Usage of a local directory
build.gradle
repositories { flatDir name: 'localRepository', dirs: 'lib' }
You can also use any Ivy resolver. You can have multiple repositories.
To access a repository:
Example 9.6. Accessing a repository
build.gradle
println repositories.localRepository.name
println repositories['localRepository'].name
To configure a repository:
Example 9.7. Configuration of a repository
build.gradle
repositories { localRepository { addArtifactPattern(file('lib').absolutePath + '/[name]/[revision]/[name]-[revision].[ext]') } } repositories.localRepository { addArtifactPattern(file('lib').absolutePath + '/[name]/[revision]/[name]-[revision].[ext]') }
To define an external dependency, you add a dependency to a configuration:
Example 9.8. Definition of an external dependency
build.gradle
configurations { compile } dependencies { compile group: 'commons-collections', name: 'commons-collections', version: '3.2' }
group
and version
are optional
TBD - configuring an external dependency
To use the external dependencies of a configuration:
Example 9.9. Usage of external dependency of a configuration
build.gradle
task listJars << { configurations.compile.each { File file -> println file.name } }
Output of gradle -q listJars
> gradle -q listJars commons-collections-3.2.jar
Configurations are contained in a ConfigurationContainer
.
Each configuration implements the Configuration
.
This chapter introduces the basics of the Gradle command-line. You run a build using the gradle command, which you have already seen in action in previous chapters.
You can execute multiple tasks in a single build by listing each of the tasks on the command-line. For example,
the command gradle compile test
will execute the compile
and
test
tasks. Gradle will execute the tasks in the order that they are listed on the
command-line, and will also execute the dependencies for each task. Each task is executed once only,
regardless of how it came to be included in the build: whether it was specified on the command-line, or it a
dependency of another task, or both. Let's look at an example.
Below four tasks are defined. Both dist
and test
depend on the
compile
task. Running gradle dist test
for this build script
results in the compile
task being executed only once.
Example 10.1. Executing multiple tasks
build.gradle
task compile << { println 'compiling source' } task compileTest(dependsOn: compile) << { println 'compiling unit tests' } task test(dependsOn: [compile, compileTest]) << { println 'running unit tests' } task dist(dependsOn: [compile, test]) << { println 'building the distribution' }
Output of gradle dist test
> gradle dist test :compile compiling source :compileTest compiling unit tests :test running unit tests :dist building the distribution BUILD SUCCESSFUL Total time: 1 secs
Because each task is executed once only, executing gradle test test
is exactly the same
as executing gradle test
.
You can exclude a task from being executed using the -x
command-line option and providing
the name of the task to exclude. Let's try this with the sample build file above.
Example 10.2. Excluding tasks
Output of gradle dist -x test
> gradle dist -x test :compile compiling source :dist building the distribution BUILD SUCCESSFUL Total time: 1 secs
You can see from the output of this example, that the test
task is not executed, even
though it is a dependency of the dist
task. You will also notice that the
test
task's dependencies, such as compileTest
are not executed either. Those dependencies of test
that are required by another task, such as
compile
, are still executed.
When you specify tasks on the command-line, you don't have to provide the full name of the task. You only need to provide enough of the
task name to uniquely identify the task. For example, in the sample build above, you can execute task
dist
by running gradle d
:
Example 10.3. Abbreviated task name
Output of gradle di
> gradle di :compile compiling source :compileTest compiling unit tests :test running unit tests :dist building the distribution BUILD SUCCESSFUL Total time: 1 secs
You can also abbreviate each word in a camel case task name. For example, you can execute task compileTest
by running gradle compTest
or even gradle cT
Example 10.4. Abbreviated camel case task name
Output of gradle cT
> gradle cT :compile compiling source :compileTest compiling unit tests BUILD SUCCESSFUL Total time: 1 secs
You can also use these abbreviations with the -x
command-line option.
When you run the gradle command, it looks for a build file in the current directory.
You can use the -b
option to select another build file. For example:
Example 10.5. Selecting the project using a build file
subdir/myproject.gradle
task hello << {
println "using build file '$buildFile.name' in '$buildFile.parentFile.name'."
}
Output of gradle -q -b subdir/myproject.gradle hello
> gradle -q -b subdir/myproject.gradle hello using build file 'myproject.gradle' in 'subdir'.
Alternatively, you can use the -p
option to specify the project directory to use:
Example 10.6. Selecting the project using project directory
Output of gradle -q -p subdir hello
> gradle -q -p subdir hello using build file 'build.gradle' in 'subdir'.
Gradle provides several built-in tasks which show particular details of your build. This can be useful for understanding the structure and dependencies of your build, and for debugging problems.
In addition to the built-in tasks shown below, you can also use the project report plugin to add tasks to your project which will generate these reports.
Running gradle projects
gives you a list of the sub-projects of the selected project,
displayed in a hierarchy. Here is an example:
Example 10.7. Obtaining information about projects
Output of gradle -q projects
> gradle -q projects ------------------------------------------------------------ Root Project ------------------------------------------------------------ Root project 'projectReports' +--- Project ':api' - The shared API for the application \--- Project ':webapp' - The Web application implementation To see a list of the tasks of a project, run gradle <project-path>:tasks For example, try running gradle :api:tasks
The report shows the description of each project, if specified. You can provide a description for a project
by setting the description
property:
Example 10.8. Providing a description for a project
build.gradle
description = 'The shared API for the application'
Running gradle tasks
gives you a list of the main tasks of the
selected project. This report shows the default tasks for the project, if any, and a description for
each task. Below is an example of this report:
Example 10.9. Obtaining information about tasks
Output of gradle -q tasks
> gradle -q tasks ------------------------------------------------------------ Root Project ------------------------------------------------------------ Default tasks: dists Build tasks ----------- clean - Deletes the build directory (build) dists - Builds the distribution libs - Builds the JAR Help tasks ---------- dependencies - Displays the dependencies of root project 'projectReports'. help - Displays a help message projects - Displays the sub-projects of root project 'projectReports'. properties - Displays the properties of root project 'projectReports'. tasks - Displays the tasks in root project 'projectReports'. To see all tasks and more detail, run with --all.
By default, this report shows only those tasks which have been assigned to a task group. You can do this
by setting the group
property for the task. You can also set the description
property, to provide a description to be included in the report.
Example 10.10. Changing the content of the task report
build.gradle
dists { description = 'Builds the distribution' group = 'build' }
You can obtain more information in the task listing using the --all
option. With
this option, the task report lists all tasks in the project, grouped by main task, and the dependencies
for each task. Here is an example:
Example 10.11. Obtaining more information about tasks
Output of gradle -q tasks --all
> gradle -q tasks --all ------------------------------------------------------------ Root Project ------------------------------------------------------------ Default tasks: dists Build tasks ----------- clean - Deletes the build directory (build) api:clean - Deletes the build directory (build) webapp:clean - Deletes the build directory (build) dists - Builds the distribution [api:libs, webapp:libs] docs - Builds the documentation api:libs - Builds the JAR api:compile - Compiles the source files webapp:libs - Builds the JAR [api:libs] webapp:compile - Compiles the source files Help tasks ---------- dependencies - Displays the dependencies of root project 'projectReports'. help - Displays a help message projects - Displays the sub-projects of root project 'projectReports'. properties - Displays the properties of root project 'projectReports'. tasks - Displays the tasks in root project 'projectReports'.
Running gradle dependencies
gives you a list of the dependencies of the selected project, broken down by configuration. For each
configuration, the direct and transitive dependencies of that configuration are shown in a tree. Below
is an example of this report:
Example 10.12. Obtaining information about dependencies
Output of gradle -q dependencies api:dependencies webapp:dependencies
> gradle -q dependencies api:dependencies webapp:dependencies ------------------------------------------------------------ Root Project ------------------------------------------------------------ No configurations ------------------------------------------------------------ Project :api - The shared API for the application ------------------------------------------------------------ compile \--- org.codehaus.groovy:groovy-all:1.7.10 [default] ------------------------------------------------------------ Project :webapp - The Web application implementation ------------------------------------------------------------ compile +--- projectReports:api:1.0-SNAPSHOT [compile] | \--- org.codehaus.groovy:groovy-all:1.7.10 [default] \--- commons-io:commons-io:1.2 [default]
Running gradle properties
gives you a list of the properties of the selected
project. This is a snippet from the output:
Example 10.13. Information about properties
Output of gradle -q api:properties
> gradle -q api:properties ------------------------------------------------------------ Project :api - The shared API for the application ------------------------------------------------------------ additionalProperties: {} all: [task ':api:clean', task ':api:compile', task ':api:libs'] allprojects: [project ':api'] ant: org.gradle.api.internal.project.DefaultAntBuilder@12345 antBuilderFactory: org.gradle.api.internal.project.DefaultAntBuilderFactory@12345 artifacts: org.gradle.api.internal.artifacts.dsl.DefaultArtifactHandler@12345 asDynamicObject: org.gradle.api.internal.DynamicObjectHelper@12345 asMap: {clean=task ':api:clean', compile=task ':api:compile', libs=task ':api:libs'} buildDir: /home/user/gradle/samples/userguide/tutorial/projectReports/api/build buildDirName: build buildFile: /home/user/gradle/samples/userguide/tutorial/projectReports/api/build.gradle
The --profile
command line option will record some useful timing information
while your build is running and write a report to the build/reports/profile
directory.
The report will be named using the time when the build was run.
This report lists summary times and details for both the configuration phase and task execution. The times for configuration and task execution are sorted with the most expensive operations first. The task execution results also indicate if any tasks were skipped (and the reason) or if tasks that were not skipped did no work.
Builds which utilize a buildSrc directory will generate a second profile report for buildSrc in the
buildSrc/build
directory.
Sometimes you are interested in which tasks are executed in which order for a given set of tasks specified on the
command line, but you don't want the tasks to be executed. You can use the -m
option for this.
For example gradle -m clean compile
shows you all tasks to be executed as
part of the clean
and compile
tasks.
This is complementary to the tasks
task, which shows you the tasks which are available for
execution.
In this chapter, you have seen some of the things you can do with Gradle from the command-line. You can find out more about the gradle command in Appendix C, Gradle Command Line.
In addition to supporting a traditional command line interface, gradle offers a graphical user interface. This is a stand alone user interface that can be launched with the --gui option.
Note that this command blocks until the gradle GUI is closed. Under *nix it is probably preferable to run this as a background task (gradle --gui&)
If you run this from your gradle project working directory, you should see a tree of tasks.
It is preferable to run this command from your gradle project directory so that the settings of the UI will be stored in your project directory. However, you can run it then change the working directory via the Setup tab in the UI.
The UI displays 4 tabs along the top and an output window along the bottom.
The Task Tree shows a hierarchical display of all projects and their tasks. Double clicking a task executes it.
There is also a filter so that uncommon tasks can be hidden. You can toggle the filter via the Filter button. Editing the filter allows you to configure which tasks and projects are shown. Hidden tasks show up in red. Note: newly created tasks will show up by default (versus being hidden by default).
The Task Tree context menu provides the following options:
Execute ignoring dependencies. This does not require dependent projects to be rebuilt (same as the -a option).
Add tasks to the favorites (see Favorites tab)
Hide the selected tasks. This adds them to the filter.
Edit the build.gradle file. Note: this requires Java 1.6 or higher and requires that you have .gradle files associated in your OS.
The Favorites tab is place to store commonly-executed commands. These can be complex commands (anything that's legal to gradle) and you can provide them with a display name. This is useful for creating, say, a custom build command that explicitly skips tests, documentation, and samples that you could call "fast build".
You can reorder favorites to your liking and even export them to disk so they can imported by others. If you edit them, you are given options to "Always Show Live Output." This only applies if you have 'Only Show Output When Errors Occur'. This override always forces the output to be shown.
The Command Line tab is place to execute a single gradle command directly. Just enter whatever you would normally enter after 'gradle' on the command line. This also provides a place to try out commands before adding them to favorites.
The Setup tab allows configuration of some general settings.
Current Directory
Defines the root directory of your gradle project (typically where build.gradle is located).
Stack Trace Output
This determines how much information to write out stack traces when errors occur. Note: if you specify a stack trace level on either the Command Line or Favorites tab, it will override this stack trace level.
Only Show Output When Errors Occur
Enabling this option hides any output when a task is executed unless the build fails.
Use Custom Gradle Executor - Advanced feature
This provides you with an alternate way to launch gradle commands. This is useful if your project requires some extra setup that is done inside another batch file or shell script (such as specifying an init script).
There is a common situation, that multiple tasks depend on the existence of a directory. Of course you can
deal with this by adding a
mkdir
to the beginning of those tasks. But this is kind of bloated. There is a better solution (works only if the
tasks that need the directory have a
dependsOn
relationship):
Example 12.1. Directory creation with mkdir
build.gradle
classesDir = new File('build/classes') task resources << { classesDir.mkdirs() // do something } task compile(dependsOn: 'resources') << { if (classesDir.isDirectory()) { println 'The class directory exists. I can operate' } // do something }
Output of gradle -q compile
> gradle -q compile The class directory exists. I can operate
But Gradle offers you also Directory Tasks to deal with this.
Example 12.2. Directory creation with Directory tasks
build.gradle
classes = dir('build/classes') task resources(dependsOn: classes) << { // do something } task otherResources(dependsOn: classes) << { if (classes.dir.isDirectory()) { println 'The class directory exists. I can operate' } // do something }
Output of gradle -q otherResources
> gradle -q otherResources The class directory exists. I can operate
A Directory Task is a simple task whose name is a relative path to the project dir [3] . During the execution phase the directory corresponding to this path gets created if it does not exist yet. Another interesting thing to note in this example, is that you can also pass tasks objects to the dependsOn declaration of a task.
Gradle offers a variety of ways to add properties to your build. With the -D
command line
option you can pass a system property to the JVM which runs Gradle. The -D
option of the
gradle command has the same effect as the -D
option of the
java command.
You can also directly add properties to your project objects using properties files. You can place a
gradle.properties
file in the Gradle user home directory (defaults to
) or in your project directory. For
multi-project builds you can place USER_HOME
/.gradlegradle.properties
files in any subproject directory.
The properties of the gradle.properties
can be accessed via the project object. The
properties file in the user's home directory has precedence over property files in the project directories.
You can also add properties directly to your project object via the -P
command line option. For more exotic use cases you can even pass properties directly
to the project object via system and environment properties. For example if you run a build on a continuous
integration server where you have no admin rights for the machine. Your build script
needs properties which values should not be seen by others. Therefore you can't use the -P
option. In this case you can add an environment property in the project administration section (invisible to
normal users).
[4]
If the environment property follows the pattern
ORG_GRADLE_PROJECT_
,
propertyName
=somevaluepropertyName
is added to your project object. If in the future CI servers support Gradle
directly, they might start Gradle via its main method. Therefore we already support the same mechanism for
system properties. The only difference is the pattern, which is
org.gradle.project.
.
propertyName
With the gradle.properties
files you can also set system properties. If a property
in such a file has the prefix systemProp.
the property and its value are added to the
system properties, without the prefix.
Example 12.3. Setting properties with a gradle.properties file
gradle.properties
gradlePropertiesProp=gradlePropertiesValue systemPropertiesProp=shouldBeOverWrittenBySystemProp envPropertiesProp=shouldBeOverWrittenByEnvProp systemProp.system=systemValue
build.gradle
task printProps << {
println commandLineProjectProp
println gradlePropertiesProp
println systemProjectProp
println envProjectProp
println System.properties['system']
}
Output of gradle -q -PcommandLineProjectProp=commandLineProjectPropValue -Dorg.gradle.project.systemProjectProp=systemPropertyValue printProps
> gradle -q -PcommandLineProjectProp=commandLineProjectPropValue -Dorg.gradle.project.systemProjectProp=systemPropertyValue printProps commandLineProjectPropValue gradlePropertiesValue systemPropertyValue envPropertyValue systemValue
You can access a project property in your build script simply by using its name as you would use a
variable. In case this property does not exists, an exception is thrown and the build fails. If your
build script relies on optional properties the user might set for example in a gradle.properties file,
you need to check for existence before you can access them. You can do this by using the method
hasProperty('propertyName')
which returns
true
or false
.
Setting a proxy for web access (for example for downloading dependencies) is easy. Gradle does not need to
provide special functionality for this. The JVM can be instructed to go via proxy by setting certain system
properties. You could set these system properties directly in your build script with
System.properties['proxy.proxyUser'] = 'userid'
. An arguably nicer way is shown in
Section 12.2, “Gradle properties and system properties”. Your gradle.properties file could look like
this:
Example 12.4. Accessing the web via a proxy
gradle.properties
systemProp.http.proxyHost=www.somehost.org systemProp.http.proxyPort=8080 systemProp.http.proxyUser=userid systemProp.http.proxyPassword=password systemProp.http.nonProxyHosts=*.nonproxyrepos.com|localhost
We could not find a good overview for all possible proxy settings. One place to look are the constants in a file from the ant project. Here a link to the svn view. The other is a Networking Properties page from the JDK docs. If anyone knows a better overview please let us know via the mailing list.
You can configure the current project using an external build script. All of the Gradle build language is available in the external script. You can even apply other scripts from the external script.
Example 12.5. Configuring the project using an external build script
build.gradle
apply from: 'other.gradle'
other.gradle
println "configuring $project" task hello << { println 'hello from other script' }
Output of gradle -q hello
> gradle -q hello configuring root project 'configureProjectUsingScript' hello from other script
You can configure arbitrary objects in the following very readable way.
Example 12.6. Configuring arbitrary objects
build.gradle
task configure << { pos = configure(new java.text.FieldPosition(10)) { beginIndex = 1 endIndex = 5 } println pos.beginIndex println pos.endIndex }
Output of gradle -q configure
> gradle -q configure 1 5
You can also configure arbitrary objects using an external script.
Example 12.7. Configuring arbitrary objects using a script
build.gradle
task configure << { pos = new java.text.FieldPosition(10) // Apply the script apply from: 'other.gradle', to: pos println pos.beginIndex println pos.endIndex }
other.gradle
beginIndex = 1; endIndex = 5;
Output of gradle -q configure
> gradle -q configure 1 5
To improve responsiveness Gradle caches all compiled scripts by default. This includes all build scripts,
initialization scripts, and other scripts. The first time you run a build for a project, Gradle creates a
.gradle
directory in which it puts the compiled script. The next time you run this
build, Gradle uses the compiled script, if the script has not changed since it was compiled. Otherwise the
script gets compiled and the new version is stored in the cache. If you run Gradle with the
-C rebuild
option, the cached script is discarded and the script is compiled and stored
in the cache. This way you can force Gradle to rebuild the cache.
This chapter looks at some of the details of writing a build script.
Gradle provides a domain specific language, or DSL, for describing builds. This build language is based on Groovy, with some additions to make it easier to describe a build.
In the tutorial in Chapter 6, Java Quickstart we used, for example, the
apply()
method. Where does this method come from? We said earlier that the build script
defines a project in Gradle. For each project in the build creates an instance of type
Project
and associates this Project
object with
the build script. As the build script executes, it configures this Project
object:
Don't forget that your build script is simply Groovy code that drives the Gradle API. And the
Project
interface is your starting point for accessing everything
in the Gradle API. So, if you're wondering what 'tags' are available in your build script, you can
start with the documentation for the Project
interface.
Any method you call in your build script, which is not defined
in the build script, is delegated to the Project
object.
Any property you access in your build script, which is not defined
in the build script, is delegated to the Project
object.
Let's try this out and try to access the name
property of the
Project
object.
Example 13.1. Accessing property of the Project object
build.gradle
println name println project.name
Output of gradle -q check
> gradle -q check projectApi projectApi
Both println
statements print out the same property. The first uses auto-delegation to
the Project
object, for properties not defined in the build script. The other
statement uses the project
property available to any build script, which returns the
associated Project
object. Only if you define a property or a method which has the
same name as a member of the Project
object, you need to use the project
property.
The Project
object provides some standard properties, which are available in
your build script. The following table lists a few of the commonly used ones.
Table 13.1. Project Properties
Name | Type | Default Value |
project |
Project |
The Project instance |
name |
String |
The name of the project directory. |
path |
String |
The absolute path of the project. |
description |
String |
A description for the project. |
projectDir |
File |
The directory containing the build script. |
buildDir |
File |
|
group |
Object |
unspecified |
version |
Object |
unspecified |
ant |
AntBuilder |
An AntBuilder instance |
When Gradle executes a script, it compiles the script into a class which implements Script
.
This means that all of the properties and methods declared by the Script
interface
are available in your script.
Groovy provides plenty of features for creating DSLs, and the Gradle build language takes advantage of these. Understanding how the build language works will help you when you write your build script, and in particular, when you start to write customs plugins and tasks.
Groovy adds lots of useful methods to JVM classes. For example, Iterable
gets
an each
method, which iterates over the elements of the Iterable
:
Example 13.2. Groovy JDK methods
build.gradle
// Iterable gets an each() method
configurations.runtime.each { File f -> println f }
Have a look at http://groovy.codehaus.org/groovy-jdk/ for more details.
Groovy automatically converts a property reference into a call to the appropriate getter or setter method.
Example 13.3. Property accessors
build.gradle
// Using a getter method println project.buildDir println getProject().getBuildDir() // Using a setter method project.buildDir = 'target' getProject().setBuildDir('target')
Parentheses are optional for method calls.
Example 13.4. Method call without parentheses
build.gradle
test.systemProperty 'some.prop', 'value' test.systemProperty('some.prop', 'value')
Groovy provides some shortcuts for defining List
and Map
instances.
Example 13.5. List and map literals
build.gradle
// List literal test.includes = ['org/gradle/api/**', 'org/gradle/internal/**'] List<String> list = new ArrayList<String>() list.add('org/gradle/api/**') list.add('org/gradle/internal/**') test.includes = list // Map literal apply plugin: 'java' Map<String, String> map = new HashMap<String, String>() map.put('plugin', 'java') apply(map)
The Gradle DSL uses closures in many places. You can find out more about closures here. When the last parameter of a method is a closure, you can place the closure after the method call:
Example 13.6. Closure as method parameter
build.gradle
repositories { println "in a closure" } repositories() { println "in a closure" } repositories({ println "in a closure" })
Each closure has a delegate
object, which Groovy uses to look up variable and method
references which are not local variables or parameters of the closure. Gradle uses this for
configuration closures, where the delegate
object is set to
the object to be configured.
Example 13.7. Closure delegates
build.gradle
dependencies { assert delegate == project.dependencies compile('junit:junit:4.8.2') delegate.compile('junit:junit:4.8.2') }
In the introductory tutorial (Chapter 5, Build Script Basics) you have learned how to create simple tasks. You have also learned how to add additional behavior to these tasks later on. And you have learned how to create dependencies between tasks. This was all about simple tasks. But Gradle takes the concept of tasks further. Gradle supports enhanced tasks, that is, tasks which have their own properties and methods. This is really different to what you are used to with Ant targets. Such enhanced tasks are either provided by you or are provided by Gradle.
We have already seen how to define tasks using a keyword style in Chapter 5, Build Script Basics. There are a few variations on this style, which you may need to use in certain situations. For example, the keyword style does not work in expressions.
Example 14.1. Defining tasks
build.gradle
task(hello) << { println "hello" } task(copy, type: Copy) { from(file('srcDir')) into(buildDir) }
You can also use strings for the task names:
Example 14.2. Defining tasks - using strings
build.gradle
task('hello') << { println "hello" } task('copy', type: Copy) { from(file('srcDir')) into(buildDir) }
There is an alternative syntax for defining tasks, which you may prefer to use:
Example 14.3. Defining tasks with alternative syntax
build.gradle
tasks.add(name: 'hello') << { println "hello" } tasks.add(name: 'copy', type: Copy) { from(file('srcDir')) into(buildDir) }
Here we add tasks to the tasks
collection. Have a look at
TaskContainer
for more variations of the add()
method.
You often need to locate the tasks that you have defined in the build file, for example, to configure them or use them for dependencies. There are a number of ways you can do this. Firstly, each task is available as a property of the project, using the task name as the property name:
Example 14.4. Accessing tasks as properties
build.gradle
task hello println hello.name println project.hello.name
Tasks are also available through the tasks
collection.
Example 14.5. Accessing tasks via tasks collection
build.gradle
task hello
println tasks.hello.name
println tasks['hello'].name
You can access tasks from any project using the task's path using the tasks.getByPath()
method. You can call the getByPath()
method with a task name, or a relative path, or an
absolute path.
Example 14.6. Accessing tasks by path
build.gradle
project(':projectA') { task hello } task hello println tasks.getByPath('hello').path println tasks.getByPath(':hello').path println tasks.getByPath('projectA:hello').path println tasks.getByPath(':projectA:hello').path
Output of gradle -q hello
> gradle -q hello :hello :hello :projectA:hello :projectA:hello
Have a look at TaskContainer
for more options for locating tasks.
As an example, let's look at the Copy
task provided by Gradle. To create a
Copy
task for your build, you can declare in your build script:
This creates a copy task with no default behavior.
The task can be configured using its API (see Copy
).
The following examples show several different ways to achieve the same configuration.
Example 14.8. Configuring a task - various ways
build.gradle
Copy myCopy = task(myCopy, type: Copy) myCopy.from 'resources' myCopy.into 'target' myCopy.include('**/*.txt', '**/*.xml', '**/*.properties')
This is similar to the way we would normally configure objects in Java. You have to repeat the context
(myCopy
) in the configuration statement every time. This is a redundancy and not very
nice to read.
There is a more convenient way of doing this.
Example 14.9. Configuring a task - fluent interface
build.gradle
task(myCopy, type: Copy) .from('resources') .into('target') .include('**/*.txt', '**/*.xml', '**/*.properties')
You might know this approach from the Hibernates Criteria Query API or JMock. Of course the API of a task
has to support this. The from
, to
and include
methods all return an object that may be used to chain to additional configuration methods. Gradle's build-in tasks usually
support this configuration style.
But there is yet another way of configuring a task. It also preserves the context and it is arguably the most readable. It is usually our favorite.
Example 14.10. Configuring a task - with closure
build.gradle
task myCopy(type: Copy) myCopy { from 'resources' into 'target' include('**/*.txt', '**/*.xml', '**/*.properties') }
This works for any task. Line 3 of the example is just a shortcut for the
tasks.getByName()
method. It is important to note that if you pass a closure to the
getByName()
method, this closure is applied to configure the task.
There is a slightly different ways of doing this.
Example 14.11. Configuring a task - with configure() method
build.gradle
task myCopy(type: Copy) myCopy.configure { from('source') into('target') include('**/*.txt', '**/*.xml', '**/*.properties') }
Every task has a configure()
method, which you can pass a closure for configuring the task.
Gradle uses this style for configuring objects in many places, not just for tasks.
You can also use a configuration closure when you define a task.
Example 14.12. Defining a task with closure
build.gradle
task copy(type: Copy) { from 'resources' into 'target' include('**/*.txt', '**/*.xml', '**/*.properties') }
There are several ways you can define the dependencies of a task. In
Section 5.5, “Task dependencies”
you were introduced to defining dependencies using task names. Task names can refer to tasks in the same
project as the task, or to tasks in other projects. To refer to a task in another project, you prefix the
name of the task with the path of the project it belongs to. Below is an example which adds a dependency
from
projectA:taskX
to
projectB:taskY
:
Example 14.13. Adding dependency on task from another project
build.gradle
project('projectA') { task taskX(dependsOn: ':projectB:taskY') << { println 'taskX' } } project('projectB') { task taskY << { println 'taskY' } }
Output of gradle -q taskX
> gradle -q taskX taskY taskX
Instead of using a task name, you can define a dependency using a
Task
object, as shown in this example:
Example 14.14. Adding dependency using task object
build.gradle
task taskX << { println 'taskX' } task taskY << { println 'taskY' } taskX.dependsOn taskY
Output of gradle -q taskX
> gradle -q taskX taskY taskX
For more advanced uses, you can define a task dependency using a closure. When evaluated, the closure is
passed the task whose dependencies are being calculated. The closure should return a single
Task
or collection of Task
objects, which are then treated
as dependencies of the task. The following example adds a dependency from taskX
to all the tasks in the project whose name starts with lib
:
Example 14.15. Adding dependency using closure
build.gradle
task taskX << { println 'taskX' } taskX.dependsOn { tasks.findAll { task -> task.name.startsWith('lib') } } task lib1 << { println 'lib1' } task lib2 << { println 'lib2' } task notALib << { println 'notALib' }
Output of gradle -q taskX
> gradle -q taskX lib1 lib2 taskX
For more information about task dependencies, see the Task
API.
You can add a description to your task. This description is for example displayed when executing
gradle tasks
.
Example 14.16. Adding a description to a task
build.gradle
task copy(type: Copy) { description = 'Copies the resource directory to the target directory.' from 'resources' into 'target' include('**/*.txt', '**/*.xml', '**/*.properties') }
Sometimes you want to replace a task. For example if you want to exchange a task added by the Java plugin with a custom task of a different type. You can achieve this with:
Example 14.17. Overwriting a task
build.gradle
task copy(type: Copy)
task copy(overwrite: true) << {
println('I am the new one.')
}
Output of gradle -q copy
> gradle -q copy I am the new one.
Here we replace a task of type Copy
with a simple task. When creating the simple
task, you have to set the overwrite
property to true. Otherwise Gradle throws an
exception, saying that a task with such a name already exists.
Gradle offers multiple ways to skip the execution of a task.
You can use the onlyIf()
method to attach a predicate to a task. The task's
actions are only executed if the predicate evaluates to true. You implement the predicate as a closure.
The closure is passed the task as a parameter, and should return true if the task should execute
and false if the task should be skipped. The predicate is evaluated just before the task is due
to be executed.
Example 14.18. Skipping a task using a predicate
build.gradle
task hello << { println 'hello world' } hello.onlyIf { !project.hasProperty('skipHello') }
Output of gradle hello -PskipHello
> gradle hello -PskipHello :hello SKIPPED BUILD SUCCESSFUL Total time: 1 secs
If the rules for skipping a task can't be expressed with predicate, you can use the
StopExecutionException
. If this exception is thrown by an action,
the further execution of this action as well as the execution of
any following action of this task is skipped. The build continues with executing the next task.
Example 14.19. Skipping tasks with StopExecutionException
build.gradle
task compile << { println 'We are doing the compile.' } compile.doFirst { // Here you would put arbitrary conditions in real life. But we use this as an integration test, so we want defined behavior. if (true) { throw new StopExecutionException() } } task myTask(dependsOn: 'compile') << { println 'I am not affected' }
Output of gradle -q myTask
> gradle -q myTask I am not affected
This feature is helpful if you work with tasks provided by Gradle. It allows you to add conditional execution of the built-in actions of such a task. [5]
Every task has also an enabled
flag which defaults to true
. Setting it to false
prevents the
execution of any of the task's actions.
Example 14.20. Enabling and disabling tasks
build.gradle
task disableMe << {
println 'This should not be printed if the task is disabled.'
}
disableMe.enabled = false
Output of gradle disableMe
> gradle disableMe :disableMe SKIPPED BUILD SUCCESSFUL Total time: 1 secs
If you are using one of the tasks that come with Gradle, such as a task added by the Java plugin, you might have noticed that Gradle will skip tasks that are up-to-date. This behaviour is also available for your tasks, not just for built-in tasks.
Let's have a look at an example. Here our task generates several output files from a source XML file. Let's run it a couple of times.
Example 14.21. A generator task
build.gradle
task transform { srcFile = file('mountains.xml') destDir = new File(buildDir, 'generated') doLast { println "Transforming source file." destDir.mkdirs() def mountains = new XmlParser().parse(srcFile) mountains.mountain.each { mountain -> def name = mountain.name[0].text() def height = mountain.height[0].text() def destFile = new File(destDir, "${name}.txt") destFile.text = "$name -> ${height}\n" } } }
Output of gradle transform
> gradle transform :transform Transforming source file.
Output of gradle transform
> gradle transform :transform Transforming source file.
Notice that Gradle executes this task a second time, and does not skip the task even though nothing has changed. Our example task was defined using an action closure. Gradle has no idea what the closure does and cannot automatically figure out whether the task is up-to-date or not. To use Gradle's up-to-date checking, you need to declare the inputs and outputs of the task.
Each task has an inputs
and outputs
property, which you use to
declare the inputs and outputs of the task. Below, we have changed our example to declare that it takes
the source XML file as an input and produces output to a destination directory. Let's run it a couple
of times.
Example 14.22. Declaring the inputs and outputs of a task
build.gradle
task transform { srcFile = file('mountains.xml') destDir = new File(buildDir, 'generated') inputs.file srcFile outputs.dir destDir doLast { println "Transforming source file." destDir.mkdirs() def mountains = new XmlParser().parse(srcFile) mountains.mountain.each { mountain -> def name = mountain.name[0].text() def height = mountain.height[0].text() def destFile = new File(destDir, "${name}.txt") destFile.text = "$name -> ${height}\n" } } }
Output of gradle transform
> gradle transform :transform Transforming source file.
Output of gradle transform
> gradle transform :transform UP-TO-DATE
Now, Gradle knows which files to check to determine whether the task is up-to-date or not.
The task's inputs
property is of type TaskInputs
.
The task's outputs
property is of type TaskOutputs
.
Before a task is executed for the first time, Gradle takes a snapshot of the inputs. This snapshot contains the set of input files and a hash of the contents of each file. Gradle then executes the task. If the task completes successfully, Gradle takes a snapshot of the outputs. This snapshot contains the set of output files and a hash of the contents of each file. Gradle takes note of any files created, changed or deleted in the output directories of the task. Gradle persists both snapshots for next time the task is executed.
Each time after that, before the task is executed, Gradle takes a new snapshot of the inputs and outputs. If the new snapshots are the same as the previous snapshots, Gradle assumes that the outputs are up to date and skips the task. If they are not the same, Gradle executes the task. Gradle persists both snapshots for next time the task is executed.
Sometimes you want to have a task which behavior depends on a large or infinite number value range of parameters. A very nice and expressive way to provide such tasks are task rules:
Example 14.23. Task rule
build.gradle
tasks.addRule("Pattern: ping<ID>") { String taskName -> if (taskName.startsWith("ping")) { task(taskName) << { println "Pinging: " + (taskName - 'ping') } } }
Output of gradle -q pingServer1
> gradle -q pingServer1 Pinging: Server1
The String parameter is used as a description for the rule. This description is shown when running
for example gradle tasks
.
Rules not just work for calling tasks from the command line. You can also create dependsOn relations on rule based tasks:
Example 14.24. Dependency on rule based tasks
build.gradle
tasks.addRule("Pattern: ping<ID>") { String taskName -> if (taskName.startsWith("ping")) { task(taskName) << { println "Pinging: " + (taskName - 'ping') } } } task groupPing { dependsOn pingServer1, pingServer2 }
Output of gradle -q groupPing
> gradle -q groupPing Pinging: Server1 Pinging: Server2
If you are coming from Ant, such an enhanced Gradle task as Copy looks like a mixture between an Ant target and an Ant task. And this is actually the case. The separation that Ant does between tasks and targets is not done by Gradle. The simple Gradle tasks are like Ant's targets and the enhanced Gradle tasks also include the Ant task aspects. All of Gradle's tasks share a common API and you can create dependencies between them. Such a task might be nicer to configure than an Ant task. It makes full use of the type system, is more expressive and easier to maintain.
[5] You might be wondering why there is neither an import for the
StopExecutionException
nor do we access it via its fully qualified name. The reason is, that Gradle adds a set of default imports
to your script. These imports are customizable (see Appendix D, Existing IDE Support and how to cope without it).
Most builds work with files. Gradle adds some concepts and APIs to help you achieve this.
You can locate a file relative to the project directory using the
Project.file()
method.
Example 15.1. Locating files
build.gradle
// Using a relative path File configFile = file('src/config.xml') // Using an absolute path configFile = file(configFile.absolutePath) // Using a File object with a relative path configFile = file(new File('src/config.xml'))
You can pass any object to the file()
method, and it will attempt to convert the value
to an absolute File
object. Usually, you would pass it a
String
or File
instance. The supplied object's
toString()
value is used as the file path. If this path is an absolute path, it is used
to construct a File
instance. Otherwise, a File
instance is
constructed by prepending the project directory path to the supplied path. The file()
method also understands URLs, such as file:/some/path.xml
.
Using this method is a useful way to convert some user provided value into an absolute File
.
It is preferable to using new File(somePath)
, as file()
always evaluates
the supplied path relative to the project directory, which is fixed, rather than the current working
directory, which can change depending on how the user runs Gradle.
A file collection is simply a set of files. It is represented by the
FileCollection
interface. Many objects in the Gradle API implement
this interface. For example, dependency configurations implement
FileCollection
.
One way to obtain a FileCollection
instance is to use the
Project.files()
method. You can pass this method any number of
objects, which are then converted into a set of File
objects. The
files()
method accepts any type of object as its parameters. These are evaluated relative
to the project directory, as for the file()
method, described in Section 15.1, “Locating files”.
You can also pass collections, iterables, maps and arrays to the files()
method. These are flattened
and the contents converted to File
instances.
Example 15.2. Creating a file collection
build.gradle
FileCollection collection = files('src/file1.txt', new File('src/file2.txt'), ['src/file3.txt', 'src/file4.txt'])
A file collection is iterable, and can be converted to a number of other types using the as
operator. You can also add 2 file collections together using the +
operator, or subtract one
file collection from another using the -
operator.
Here are some examples of what you can do with a file collection.
Example 15.3. Using a file collection
build.gradle
// Iterate over the files in the collection collection.each {File file -> println file.name } // Convert the collection to various types Set set = collection.files Set set2 = collection as Set List list = collection as List String path = collection.asPath File file = collection.singleFile File file2 = collection as File // Add and subtract collections def union = collection + files('src/file3.txt') def different = collection - files('src/file3.txt')
You can also pass the files()
method a closure or a Callable
instance. This is called when the contents of the collection are queried, and its return value is converted
to a set of File
instances. The return value can be an object of any of the types
supported by the files()
method. This is a simple way to 'implement' the
FileCollection
interface.
Example 15.4. Implementing a file collection
build.gradle
task list << { File srcDir // Create a file collection using a closure collection = files { srcDir.listFiles() } srcDir = file('src') println "Contents of $srcDir.name" collection.collect { relativePath(it) }.sort().each { println it } srcDir = file('src2') println "Contents of $srcDir.name" collection.collect { relativePath(it) }.sort().each { println it } }
Output of gradle -q list
> gradle -q list Contents of src src/dir1 src/file1.txt Contents of src2 src2/dir1 src2/dir2
It is important to note that the content of a file collection is evaluated lazily, when it is needed.
This means you can, for example, create a FileCollection
that represents files which
will be created in the future by, say, some task.
The files()
method also accepts FileCollection
instances.
These are flattened and the contents included in the file collection.
A file tree is a collection of files arranged in a hierarchy. For example, a file tree
might represent a directory tree or the contents of a ZIP file. It is represented
by the FileTree
interface. The FileTree
interface
extends FileCollection
, so you can treat a file tree exactly the same way as you would a
file collection. Several objects in Gradle implement the FileTree
interface, such as
source sets.
One way to obtain a FileTree
instance is to use the
Project.fileTree()
method.
This creates a FileTree
defined with a base directory, and optionally some Ant-style
include and exclude patterns.
Example 15.5. Creating a file tree
build.gradle
// Create a file tree with a base directory FileTree tree = fileTree(dir: 'src/main') // Add include and exclude patterns to the tree tree.include '**/*.java' tree.exclude '**/Abstract*' // Create a tree using path tree = fileTree('src').include('**/*.java') // Create a tree using closure tree = fileTree { from 'src' include '**/*.java' } // Create a tree using a map tree = fileTree(dir: 'src', include: '**/*.java') tree = fileTree(dir: 'src', includes: ['**/*.java', '**/*.xml']) tree = fileTree(dir: 'src', include: '**/*.java', exclude: '**/*test*/**')
You use a file tree in the same way you use a file collection. You can also visit the contents of the tree, and select a sub-tree using Ant-style patterns:
Example 15.6. Using a file tree
build.gradle
// Iterate over the contents of a tree tree.each {File file -> println file } // Filter a tree FileTree filtered = tree.matching { include 'org/gradle/api/**' } // Add trees together FileTree sum = tree + fileTree(dir: 'src/test') // Visit the elements of the tree tree.visit {element -> println "$element.relativePath => $element.file" }
You can use the contents of an archive, such as a ZIP or TAR file, as a file tree. You do this using
the Project.zipTree()
and
Project.tarTree()
methods. These methods return a FileTree
instance which you can use like any other file tree or file collection. For example, you can use it to expand
the archive by copying the contents, or to merge some archives into another.
Example 15.7. Using an archive as a file tree
build.gradle
// Create a ZIP file tree using path FileTree zip = zipTree('someFile.zip') // Create a TAR file tree using path FileTree tar = tarTree('someFile.tar')
Many objects in Gradle have properties which accept a set of input files. For example, the
Compile
task has a source
property,
which defines the source files to compile. You can set the value of this property using any of the types
supported by the files() method, which we have seen in above.
This means you can set the property using, for example, a File
, String
,
collection, FileCollection
or even a closure.
Here are some examples:
Example 15.8. Specifying a set of files
build.gradle
// Use a File object to specify the source directory compile { source = file('src/main/java') } // Use a String path to specify the source directory compile { source = 'src/main/java' } // Use a collection to specify multiple source directories compile { source = ['src/main/java', '../shared/java'] } // Use a FileCollection (or FileTree in this case) to specify the source files compile { source = fileTree(dir: 'src/main/java').matching { include 'org/gradle/api/**' } } // Using a closure to specify the source files. compile { source = { // Use the contents of each zip file in the src dir file('src').listFiles().findAll {it.name.endsWith('.zip')}.collect { zipTree(it) } } }
Usually, there is a method with the same name as the property, which appends to the set of files. Again, this method accepts any of the types supported by the files() method.
Example 15.9. Specifying a set of files
build.gradle
compile { // Add some source directories use String paths source 'src/main/java', 'src/main/groovy' // Add a source directory using a File object source file('../shared/java') // Add some source directories using a closure source { file('src/test/').listFiles() } }
You can use the Copy
task to copy files. The copy task is very flexible, and allows
you to, for example, filter the contents of the files as they are copied, and to map the files names.
To use the Copy
task, you must provide a set of source files to copy, and a destination directory to copy
the files to. You may also specify how to transform the files as they are copied. You do all this using a
copy spec. A copy spec is represented by the CopySpec
interface. The
Copy
task implements this interface.
You specify the source files using the CopySpec.from()
method. To specify the destination directory, you use the CopySpec.into()
method.
Example 15.10. Copying files using the copy task
build.gradle
task copyTask(type: Copy) { from 'src/main/webapp' into 'build/explodedWar' }
The from()
method accepts any of the arguments that the
files() method does. When an argument resolves to a directory,
everything under that directory (but not the directory itself) is recursively copied into the destination
directory. When an argument resolves to a file, that file is copied into the destination directory.
When an argument resolves to a non-existing file, that argument is ignored.
The into()
accepts
any of the arguments that the file() method does. Here is another
example:
Example 15.11. Specifying copy task source files and destination directory
build.gradle
task anotherCopyTask(type: Copy) { // Copy everything under src/main/webapp from 'src/main/webapp' // Copy a single file from 'src/staging/index.html' // Copy the contents of a Zip file from zipTree('src/main/assets.zip') // Determine the destination directory later into { getDestDir() } }
You can select the files to copy using Ant-style include or exclude patterns, or using a closure:
Example 15.12. Selecting the files to copy
build.gradle
task copyTaskWithPatterns(type: Copy) { from 'src/main/webapp' into 'build/explodedWar' include '**/*.html' include '**/*.jsp' exclude { details -> details.file.name.endsWith('.html') && details.file.text.contains('staging') } }
You can also use the Project.copy()
method to copy files. It works the
same way as the task.
Example 15.13. Copying files using the copy() method
build.gradle
task copyMethod << { copy { from 'src/main/webapp' into 'build/explodedWar' include '**/*.html' include '**/*.jsp' } }
Example 15.14. Renaming files as they are copied
build.gradle
task rename(type: Copy) { from 'src/main/webapp' into 'build/explodedWar' // Use a closure to map the file name rename { String fileName -> fileName.replace('-staging-', '') } // Use a regular expression to map the file name rename '(.+)-staging-(.+)', '$1$2' rename(/(.+)-staging-(.+)/, '$1$2') }
Example 15.15. Filtering files as they are copied
build.gradle
import org.apache.tools.ant.filters.FixCrLfFilter import org.apache.tools.ant.filters.ReplaceTokens task filter(type: Copy) { from 'src/main/webapp' into 'build/explodedWar' // Substitute property references in files expand(copyright: '2009', version: '2.3.1') expand(project.properties) // Use some of the filters provided by Ant filter(FixCrLfFilter) filter(ReplaceTokens, tokens: [copyright: '2009', version: '2.3.1']) // Use a closure to filter each line filter { String line -> "[$line]" } }
Copy specs form a hierarchy. A copy spec inherits its destination path, include patterns, exclude patterns, copy actions, name mappings, filters.
Example 15.16. Nested copy specs
build.gradle
task nestedSpecs(type: Copy) { into 'build/explodedWar' exclude '**/*staging*' from('src/dist') { include '**/*.html' } into('libs') { from configurations.runtime } }
The Sync
task extends the Copy
task. When it
executes, it copies the source files into the destination directory, and then removes any files from the
destination directory which it did not copy. This can be useful for doing things such as installing your
application, creating an exploded copy of your archives, or maintaining a copy of the project's dependencies.
Here is an example which maintains a copy of the project's runtime dependencies in the build/libs
directory.
Example 15.17. Using the Sync task to copy dependencies
build.gradle
task libs(type: Sync) {
from configurations.runtime
into "$buildDir/libs"
}
A project can have as many as JAR archives as you want. You can also add WAR, ZIP and TAR archives to your project.
Archives are created using the various archive tasks:
Zip
,
Tar
,
Jar
, and
War
.
They all work the same way, so let's look at how you create a ZIP file.
Example 15.18. Creating a ZIP archive
build.gradle
apply plugin: 'java' task zip(type: Zip) { from 'src/dist' into('libs') { from configurations.runtime } }
The Java plugin adds a number of default values for the archive tasks. You can use the archive tasks without using the Java plugin, if you like. You will need to provide values for some additional properties.
The archive tasks all work exactly the same way as the Copy
task, and implement the same
CopySpec
interface. As with the Copy
task, you specify the input
files using the from()
method, and can optionally specify where they end up in the
archive using the into()
method. You can filter the contents of file, rename files, and
all the other things you can do with a copy spec.
The default name for a generated archive is
For example:
projectName
-version
.type
Example 15.19. Creation of ZIP archive
build.gradle
apply plugin: 'java' version = 1.0 task myZip(type: Zip) { from 'somedir' } println myZip.archiveName println relativePath(myZip.destinationDir) println relativePath(myZip.archivePath)
Output of gradle -q myZip
> gradle -q myZip zipProject-1.0.zip build/distributions build/distributions/zipProject-1.0.zip
This adds a Zip
archive task with the name myZip
which produces
ZIP filezipProject-1.0.zip
. It is important to distinguish between the name of the archive task
and the name of the archive generated by the archive task. The default name for archives can be
changed with the archivesBaseName
project property. The name of the archive can also be
changed at any time later on.
There are a number of properties which you can set on an archive task. These are listed below in Table 15.1, “Archive tasks - naming properties”. You can, for example, change the name of the archive:
Example 15.20. Configuration of archive task - custom archive name
build.gradle
apply plugin: 'java' version = 1.0 task myZip(type: Zip) { from 'somedir' baseName = 'customName' } println myZip.archiveName
Output of gradle -q myZip
> gradle -q myZip customName-1.0.zip
You can further customize the archive names:
Example 15.21. Configuration of archive task - appendix & classifier
build.gradle
apply plugin: 'java' archivesBaseName = 'gradle' version = 1.0 task myZip(type: Zip) { appendix = 'wrapper' classifier = 'src' from 'somedir' } println myZip.archiveName
Output of gradle -q myZip
> gradle -q myZip gradle-wrapper-1.0-src.zip
Table 15.1. Archive tasks - naming properties
Property name | Type | Default value | Description |
archiveName |
String |
If any of these properties is empty the trailing |
The base file name of the generated archive |
archivePath |
File |
|
The absolute path of the generated archive. |
destinationDir |
File |
Depends on the archive type. JARs and WARs are generated into .
ZIPs and TARs are generated into .
|
The directory to generate the archive into |
baseName |
String |
|
The base name portion of the archive file name. |
appendix |
String |
null |
The appendix portion of the archive file name. |
version |
String |
|
The version portion of the archive file name. |
classifier |
String |
null |
The classifier portion of the archive file name, |
extension |
String |
Depends on the archive type, and for TAR files, the compression type as well: zip , jar ,
war , tar , tgz or tbz2 . |
The extension of the archive file name. |
Using the Project.copySpec()
method to share content between archives.
Often you will want to publish an archive, so that it is usable from another project. This process is described in Chapter 35, Artifact Management
The log is the main 'UI' of a build tool. If it is too verbose, real warnings and problems are easily hidden by this. On the other hand you need the relevant information for figuring out if things have gone wrong. Gradle defines 6 log levels, as shown in Table 16.1, “Log levels”. There are two Gradle-specific log levels, in addition to the ones you might normally see. Those levels are QUIET and LIFECYCLE. The latter is the default, and is used to report build progress.
Table 16.1. Log levels
Level | Used for |
ERROR | Error messages |
QUIET | Important information messages |
WARNING | Warning messages |
LIFECYCLE | Progress information messages |
INFO | Information messages |
DEBUG | Debug messages |
You can use the command line switches shown in Table 16.2, “Log level command-line options” to choose different log levels. In Table 16.3, “Stacktrace command-line options” you find the command line switches which affect stacktrace logging.
Table 16.2. Log level command-line options
Option | Outputs Log Levels |
no logging options | LIFECYCLE and higher |
-q
|
QUIET and higher |
-i
|
INFO and higher |
-d
|
DEBUG and higher (that is, all log messages) |
Table 16.3. Stacktrace command-line options
Option | Meaning |
No stacktrace options | No stacktraces are printed to the console in case of a build error (e.g. a compile error). Only in
case of internal exceptions will stacktraces be printed. If the loglevel option -d
is chosen, truncated stacktraces are always printed.
|
-s
|
Truncated stacktraces are printed. We recommend this over full stacktraces. Groovy full stacktraces are extremely verbose (Due to the underlying dynamic invocation mechanisms. Yet they usually do not contain relevant information for what has gone wrong in your code.) |
-S
|
The full stacktraces are printed out. |
A simple option for logging in your build file is to write messages to standard output. Gradle redirects
anything written to standard output to it's logging system at the QUIET
log level.
Example 16.1. Using stdout to write log messages
build.gradle
println 'A message which is logged at QUIET level'
Gradle also provides a logger
property to a build script, which is an instance of
Logger
. This interface extends the SLF4J
Logger
interface and adds a few Gradle specific methods to it. Below is an example
of how this is used in the build script:
Example 16.2. Writing your own log messages
build.gradle
logger.quiet('An info log message which is always logged.') logger.error('An error log message.') logger.warn('A warning log message.') logger.lifecycle('A lifecycle info log message.') logger.info('An info log message.') logger.debug('A debug log message.') logger.trace('A trace log message.')
You can also hook into Gradle's logging system from within other classes used in the build (classes from
the buildSrc
directory for example). Simply use an SLF4J logger. You can use this
logger the same way as you use the provided logger in the build script.
Example 16.3. Using SLF4J to write log messages
build.gradle
import org.slf4j.Logger import org.slf4j.LoggerFactory Logger slf4jLogger = LoggerFactory.getLogger('some-logger') slf4jLogger.info('An info log message logged using SLF4j')
Internally, Gradle uses Ant and Ivy. Both have their own logging system. Gradle redirects their logging
output into the Gradle logging system. There is a 1:1 mapping from the Ant/Ivy log levels to the Gradle log
levels, except the Ant/Ivy TRACE
log level, which is mapped to Gradle
DEBUG
log level. This means the default Gradle log level will not show any Ant/Ivy output
unless it is an error or a warning.
There are many tools out there which still use standard output for logging. By default, Gradle redirects
standard output to the QUIET
log level and standard error to the ERROR
level. This behavior is configurable. The project object provides a
LoggingManager
, which allows you to change the log levels that
standard out or error are redirected to when your build script is evaluated.
Example 16.4. Configuring standard output capture
build.gradle
logging.captureStandardOutput LogLevel.INFO
println 'A message which is logged at INFO level'
To change the log level for standard out or error during task execution, tasks also provide a LoggingManager
.
Example 16.5. Configuring standard output capture for a task
build.gradle
task logInfo {
logging.captureStandardOutput LogLevel.INFO
doFirst {
println 'A task message which is logged at INFO level'
}
}
Gradle also provides integration with the Java Util Logging, Jakarta Commons Logging and Log4j logging toolkits. Any log messages which your build classes write using these logging toolkits will be redirected to Gradle's logging system.
You can replace much of Gradle's logging UI with your own. You might do this, for example, if you want to
customize the UI in some way - to log more or less information, or to change the formatting. You replace
the logging using the Gradle.useLogger()
method. This
is accessible from a build script, or an init script, or via the embedding API. Below is an example
init script which changes how task execution and build completion is logged.
Example 16.6. Customizing what Gradle logs
init.gradle
useLogger(new CustomEventLogger()) class CustomEventLogger extends BuildAdapter implements TaskExecutionListener { public void beforeExecute(Task task) { println "[$task.name]" } public void afterExecute(Task task, TaskState state) { println() } public void buildFinished(BuildResult result) { println 'build completed' } }
Output of gradle -I init.gradle build
> gradle -I init.gradle build [compile] compiling source [testCompile] compiling test source [test] running unit tests [build] build completed
Your logger can implement any of the listener interfaces listed below. When you register a logger, only the logging for the interfaces that it implements is replaced. Logging for the other interfaces is left untouched. You can find out more about the listener interfaces in Section 37.6, “Responding to the lifecycle in the build script”.
Gradle provides excellent integration with Ant. You can use individual Ant tasks or entire Ant builds in your Gradle builds. In fact, you will find that it's far easier and more powerful using Ant tasks in a Gradle build script, than it is to use Ant's XML format. You could even use Gradle simply as a powerful Ant task scripting tool.
Ant can be divided into two layers. The first layer is the Ant language. It provides the syntax for the
build.xml
, the handling of the targets, special constructs like macrodefs, and so on.
In other words, everything except the Ant tasks and types. Gradle understands this language, and allows you to
import your Ant build.xml
directly into a Gradle project. You can then use the targets of
your Ant build as if they were Gradle tasks.
The second layer of Ant is its wealth of Ant tasks and types, like javac
,
copy
or jar
. For this layer Gradle provides integration
simply by relying on Groovy, and the fantastic AntBuilder
.
Finally, since build scripts are Groovy scripts, you can always execute an Ant build as an external process.
Your build script may contain statements like:"ant clean compile".execute()
.
[6]
You can use Gradle's Ant integration as a path for migrating your build from Ant to Gradle. For example, you could start by importing your existing Ant build. Then you could move your dependency declarations from the Ant script to your build file. Finally, you could move your tasks across to your build file, or replace them with some of Gradle's plugins. This process can be done in parts over time, and you can have a working Gradle build during the entire process.
In your build script, a property called ant
is provided by Gradle. This is a reference
to an AntBuilder
instance. This AntBuilder
is used to
access Ant tasks, types and properties from your build script. There is a very simple mapping from Ant's
build.xml
format to Groovy, which is explained below.
You execute an Ant task by calling a method on the AntBuilder
instance. You use the task
name as the method name. For example, you execute the Ant echo
task by calling the
ant.echo()
method. The attributes of the Ant task are passed as Map parameters to the
method. Below is an example which executes the echo
task. Notice that we can also mix
Groovy code and the Ant task markup. This can be extremely powerful.
Example 17.1. Using an Ant task
build.gradle
task hello << {
String greeting = 'hello from Ant'
ant.echo(message: greeting)
}
Output of gradle hello
> gradle hello :hello [ant:echo] hello from Ant BUILD SUCCESSFUL Total time: 1 secs
You pass nested text to an Ant task by passing it as a parameter of the task method call. In this example, we
pass the message for the echo
task as nested text:
Example 17.2. Passing nested text to an Ant task
build.gradle
task hello << {
ant.echo('hello from Ant')
}
Output of gradle hello
> gradle hello :hello [ant:echo] hello from Ant BUILD SUCCESSFUL Total time: 1 secs
You pass nested elements to an Ant task inside a closure. Nested elements are defined in the same way as tasks, by calling a method with the same name as the element we want to define.
Example 17.3. Passing nested elements to an Ant task
build.gradle
task zip << { ant.zip(destfile: 'archive.zip') { fileset(dir: 'src') { include(name: '**.xml') exclude(name: '**.java') } } }
You can access Ant types in the same way that you access tasks, using the name of the type as the
method name. The method call returns the Ant data type, which you can then use directly in your build script. In the
following example, we create an Ant path
object, then iterate over the contents of it.
Example 17.4. Using an Ant type
build.gradle
task list << { def path = ant.path { fileset(dir: 'libs', includes: '*.jar') } path.list().each { println it } }
More information about AntBuilder
can be found in 'Groovy in Action' 8.4 or at the
Groovy Wiki
To make custom tasks available in your build, you use the typedef
Ant task, just
as you would in a build.xml
file. You can then refer to the custom Ant task as you
would a built-in Ant task.
Example 17.5. Using a custom Ant task
build.gradle
task check << { ant.taskdef(resource: 'checkstyletask.properties') { classpath { fileset(dir: 'libs', include: '*.jar') } } ant.checkstyle(config: 'checkstyle.xml') { fileset(dir: 'src') } }
You can use Gradle's dependency management to assemble the classpath to use for the custom tasks. To do this, you need to define a custom configuration for the classpath, then add some dependencies to the configuration. This is described in more detail in Section 34.3, “How to declare your dependencies”.
Example 17.6. Declaring the classpath for a custom Ant task
build.gradle
configurations { pmd } dependencies { pmd group: 'pmd', name: 'pmd', version: '4.2.5' }
To use the classpath configuration, use the asPath
property of the custom configuration.
Example 17.7. Using a custom Ant task and dependency management together
build.gradle
task check << { ant.taskdef(name: 'pmd', classname: 'net.sourceforge.pmd.ant.PMDTask', classpath: configurations.pmd.asPath) ant.pmd(shortFilenames: 'true', failonruleviolation: 'true', rulesetfiles: file('pmd-rules.xml').toURI().toString()) { formatter(type: 'text', toConsole: 'true') fileset(dir: 'src') } }
You can use the ant.importBuild()
method to import an Ant build into your Gradle
project. When you import an Ant build, each Ant target is treated as a Gradle task. This means you can
manipulate and execute the Ant targets in exactly the same way as Gradle tasks.
Example 17.8. Importing an Ant build
build.gradle
ant.importBuild 'build.xml'
build.xml
<project> <target name="hello"> <echo>Hello, from Ant</echo> </target> </project>
Output of gradle hello
> gradle hello :hello [ant:echo] Hello, from Ant BUILD SUCCESSFUL Total time: 1 secs
You can add a task which depends on an Ant target:
Example 17.9. Task that depends on Ant target
build.gradle
ant.importBuild 'build.xml' task intro(dependsOn: hello) << { println 'Hello, from Gradle' }
Output of gradle intro
> gradle intro :hello [ant:echo] Hello, from Ant :intro Hello, from Gradle BUILD SUCCESSFUL Total time: 1 secs
Or, you can add behaviour to an Ant target:
Example 17.10. Adding behaviour to an Ant target
build.gradle
ant.importBuild 'build.xml' hello << { println 'Hello, from Gradle' }
Output of gradle hello
> gradle hello :hello [ant:echo] Hello, from Ant Hello, from Gradle BUILD SUCCESSFUL Total time: 1 secs
It is also possible for an Ant target to depend on a Gradle task:
Example 17.11. Ant target that depends on Gradle task
build.gradle
ant.importBuild 'build.xml' task intro << { println 'Hello, from Gradle' }
build.xml
<project> <target name="hello" depends="intro"> <echo>Hello, from Ant</echo> </target> </project>
Output of gradle hello
> gradle hello :intro Hello, from Gradle :hello [ant:echo] Hello, from Ant BUILD SUCCESSFUL Total time: 1 secs
There are several ways to set an Ant property, so that the property can be used by Ant tasks. You can
set the property directly on the AntBuilder
instance. The Ant properties are also
available as a Map which you can change. You can also use the Ant property
task.
Below are some examples of how to do this.
Example 17.12. Setting an Ant property
build.gradle
ant.buildDir = buildDir ant.properties.buildDir = buildDir ant.properties['buildDir'] = buildDir ant.property(name: 'buildDir', location: buildDir)
build.xml
<echo>buildDir = ${buildDir}</echo>
Many Ant tasks set properties when they execute. There are several ways to get the value of these properties.
You can get the property directly from the AntBuilder
instance. The Ant properties are
also available as a Map. Below are some examples.
Example 17.13. Getting an Ant property
build.xml
<property name="antProp" value="a property defined in an Ant build"/>
build.gradle
println ant.antProp
println ant.properties.antProp
println ant.properties['antProp']
There are several ways to set an Ant reference:
Example 17.14. Setting an Ant reference
build.gradle
ant.path(id: 'classpath', location: 'libs') ant.references.classpath = ant.path(location: 'libs') ant.references['classpath'] = ant.path(location: 'libs')
build.xml
<path refid="classpath"/>
There are several ways to get an Ant reference:
Example 17.15. Getting an Ant reference
build.xml
<path id="antPath" location="libs"/>
build.gradle
println ant.references.antPath
println ant.references['antPath']
The Ant integration is provided by AntBuilder
.
[6] In Groovy you can execute Strings. To learn more about executing external processes with Groovy have a look in 'Groovy in Action' 9.3.2 or at the Groovy wiki
Now we look at how Gradle provides build-by-convention and out of the box functionality. These features are decoupled from the core of Gradle, and are provided via plugins. Although the plugins are decoupled, we would like to point out that the Gradle core plugins are NEVER updated or changed for a particular Gradle distribution. If there is a bug in the compile functionality of Gradle, we will release a new version of Gradle. There is no change of behavior for the lifetime of a given distribution of Gradle.
If you want to use the plugin for building a Java project, simply include
in your script. That's all. From a technological point of view plugins use just the same operations as you can use from your build scripts. That is, they use the Project and Task API. The Gradle plugins generally use this API to:
Add tasks to the project (e.g. compile, test)
Create dependencies between those tasks to let them execute in the appropriate order.
Add dependency configurations to the project.
Add a so called convention object to the project.
Let's check this out:
Example 18.2. Applying a plugin by id
build.gradle
apply plugin: 'java'
task show << {
println relativePath(compileJava.destinationDir)
println relativePath(processResources.destinationDir)
}
Output of gradle -q show
> gradle -q show build/classes/main build/classes/main
The Java plugin adds a compileJava
task and a processResources
task
to the project object which can be accessed by a build script. It has configured the destinationDir
property of both of these tasks.
The apply()
method either takes a string or a class as an argument. You can write
Thanks to Gradle's default imports (see Appendix D, Existing IDE Support and how to cope without it) you can also write in this case.
Any class, which implements the Plugin
interface, can be used as a
plugin. Just pass the class as an argument. You don't need to configure anything else for this.
If you want to use your own plugins, you must make sure that they are accessible via the build script classpath (see Chapter 41, Organizing Build Logic for more information). To learn more about how to write custom plugins, see Chapter 40, Writing Custom Plugins.
If you use the Java plugin
for example, there are a compileJava
and a processResources
task for
your production code (the same is true for your test
code). The default location for the output of those tasks is the directory build/classes/main
.
What if you want to change this? Let's try:
Example 18.5. Configuring a plugin task
build.gradle
apply plugin: 'java' task show << { processResources.destinationDir = new File(buildDir, 'output') println relativePath(processResources.destinationDir) println relativePath(compileJava.destinationDir) }
Output of gradle -q show
> gradle -q show build/output build/classes/main
Setting the destinationDir
of the processResources
task had only an effect on the processResources
task. Maybe this was what you wanted. But what if
you want to change the output directory for all tasks? It would be unfortunate if you had to do this for
each task separately.
Gradle's tasks are usually convention aware. A plugin can add a convention object to your project, and map certain values of this convention object to task properties.
Example 18.6. Plugin convention object
build.gradle
apply plugin: 'java' task show << { sourceSets.main.classesDir = new File(buildDir, 'output') println relativePath(processResources.destinationDir) println relativePath(compileJava.destinationDir) }
Output of gradle -q show
> gradle -q show build/output build/output
The Java plugin has added a convention object with a sourceSets
property, which we use to set the classes directory. Notice that setting this has changed the destinationDir
property of both the processResources
and
compileJava
tasks.
By setting a task attribute explicitly (as we have done in the first example) you overwrite the convention value for this particular task.
Not all of the tasks attributes are mapped to convention object values. It is the decision of the plugin to decide what are the shared properties and then bundle them in a convention object and map them to the tasks.
The properties of a convention object can be accessed as project properties. As shown in the following example, you can also access the convention object explicitly.
Example 18.7. Using the plugin convention object
build.gradle
apply plugin: 'java' task show << { // Access the convention property as a project property println relativePath(sourceSets.main.classesDir) println relativePath(project.sourceSets.main.classesDir) // Access the convention property via the convention object println relativePath(project.convention.sourceSets.main.classesDir) println relativePath(project.convention.plugins.java.sourceSets.main.classesDir) }
Output of gradle -q show
> gradle -q show build/classes/main build/classes/main build/classes/main build/classes/main
Every project object has a Convention
object which is a
container for convention objects contributed
by the plugins declared for your project. If you simply access or set a property or access a method in
your build script, the project object first looks if this is a property of itself. If not, it delegates
the request to its convention object. The convention object checks if any of the plugin convention
objects can fulfill the request (first wins and the order is not defined). The plugin convention objects
also introduce a namespace.
A plugin is only called once for a given project, even if you have multiple
apply()
statements. An additional call after the first call has no effect but doesn't hurt either. This can be
important if you use plugins which extend other plugins. For example
the Groovy plugin automatically applies the Java plugin. We say the Groovy plugin extends the Java plugin. But you might as well
write:
Example 18.8. Explicit application of an implied plugin
build.gradle
apply plugin: 'java' apply plugin: 'groovy'
If you use cross-project configuration in multi-project builds this is a useful feature.
There are a number of plugins included in the Gradle distribution. These are listed below.
These plugins add support for various languages which can be compiled and executed in the JVM.
Table 19.1. Language plugins
Plugin Id | Automatically applies | Works with | Description |
java
|
java-base |
- |
Adds Java compilation, testing and bundling capabilities to a project. It serves as the basis for many of the other Gradle plugins. See also Chapter 6, Java Quickstart. |
groovy
|
java , groovy-base |
- |
Adds support for building Groovy projects. See also Chapter 7, Groovy Quickstart. |
scala
|
java , scala-base |
- |
Adds support for building Scala projects. |
antlr
|
java |
- |
Adds support for generating parsers using Antlr. |
These plugins provide some integration with various build and runtime technologies.
Table 19.2. Integration plugins
Plugin Id | Automatically applies | Works with | Description |
announce
|
- | - |
Publish messages to your favourite platforms, such as Twitter or Growl. |
application
|
- |
java , groovy |
Adds tasks for running and bundling a project as application. |
jetty
|
war |
- |
Deploys your web application to a Jetty web container embedded in the build. See also Chapter 8, Web Application Quickstart. |
maven
|
- | java , war |
Adds support for deploying artifacts to Maven repositories. |
osgi
|
java-base |
java |
Adds support for building OSGi bundles. |
war
|
java |
- |
Adds support for assembling web application WAR files. See also Chapter 8, Web Application Quickstart. |
These plugins provide help with your software development process.
Table 19.3. Software development plugins
Plugin Id | Automatically applies | Works with | Description |
code-quality
|
reporting-base |
java , groovy |
Performs code quality checks and generate reports from these checks. |
eclipse
|
- | java , groovy , scala , war |
Generates files that are used by Eclipse IDE, thus making it possible to import the project into Eclipse. See also Chapter 6, Java Quickstart. |
idea
|
- | java |
Generates files that are used by Intellij IDEA IDE, thus making it possible to import the project into IDEA. |
project-report
|
reporting-base |
- |
Generates reports containing useful information about your Gradle build. |
sonar
|
- | - |
Provides integration with the Sonar code quality platform. |
These plugins form the basic building blocks which the other plugins are assembled from. They are available for you to use in your build files, and are listed here for completeness. However, be aware that they are not yet considered part of Gradle's public API. As such, these plugins are not documented in the user guide. You might refer to their API documentation to learn more about them.
Table 19.4. Base plugins
Plugin Id | Description |
base | Adds the standard lifecycle tasks to the project, plus some shared convention properties. |
java-base | Adds the source sets concept to the project. Does not add any particular source sets. |
groovy-base | Adds the Groovy source sets concept to the project. |
scala-base | Adds the Scala source sets concept to the project. |
reporting-base | Adds some shared convention properties to the project, relating to report generation. |
You can find a list of external plugins on the wiki.
The Java plugin adds Java compilation, testing and bundling capabilities to a project. It serves as the basis for many of the other Gradle plugins.
To use the Java plugin, include in your build script:
The Java plugin introduces the concept of a source set. A source set is a group of source files which are compiled and executed together. These source files may include Java source files and resource files. Other plugins add the ability to include Groovy and Scala source files in a source set. A source set has an associated compile classpath, and runtime classpath.
You might use a source set to define an integration test suite, or for the API classes of your project, or to separate source which needs to be compiled against different Java versions.
The Java plugin defines two standard source sets, called main
and test
.
The main
source set contains your production source code, which is compiled and assembled
into a JAR file. The test
source set contains your unit test source code, which is
compiled and executed using JUnit or TestNG.
The Java plugin adds a number of tasks to your project, as shown below.
Table 20.1. Java plugin - tasks
Task name | Depends on | Type | Description |
compileJava
|
All tasks which produce the compile classpath. This includes the jar task for
project dependencies included in the compile configuration.
|
Compile |
Compiles production Java source files using javac. |
processResources
|
- | Copy |
Copies production resources into the production classes directory. |
classes
|
compileJava and processResources .
Some plugins add additional compilation tasks.
|
Task |
Assembles the production classes directory. |
compileTestJava
|
compile , plus all tasks which produce the test compile classpath.
|
Compile |
Compiles test Java source files using javac. |
processTestResources
|
- | Copy |
Copies test resources into the test classes directory. |
testClasses
|
compileTestJava and processTestResources .
Some plugins add additional test compilation tasks.
|
Task |
Assembles the test classes directory. |
jar
|
compile
|
Jar |
Assembles the JAR file |
javadoc
|
compile |
Javadoc |
Generates API documentation for the production Java source, using Javadoc |
test
|
compile ,
compileTest ,
plus all tasks which produce the test runtime classpath.
|
Test |
Runs the unit tests using JUnit or TestNG. |
uploadArchives
|
The tasks which produce the artifacts in the archives configuration, including jar .
|
Upload |
Uploads the artifacts in the archives configuration, including the JAR file. |
clean
|
- | Delete |
Deletes the project build directory. |
clean
|
- | Delete |
Deletes the output files produced by the specified task. For example cleanJar
will delete the JAR file created by the jar task, and
cleanTest will delete the test results created by the test task.
|
For each source set you add to the project, the Java plugin adds the following compilation tasks:
Table 20.2. Java plugin - source set tasks
Task name | Depends on | Type | Description |
compile
|
All tasks which produce the source set's compile classpath. | Compile |
Compiles the given source set's Java source files using javac. |
process
|
- | Copy |
Copies the given source set's resources into the classes directory. |
|
compile and
process .
Some plugins add additional compilation tasks for the source set.
|
Task |
Assembles the given source set's classes directory. |
The Java plugin also adds a number of tasks which form a lifecycle for the project:
Table 20.3. Java plugin - lifecycle tasks
Task name | Depends on | Type | Description |
assemble
|
All archive tasks in the project, including jar . Some plugins add additional
archive tasks to the project.
|
Task |
Assembles all the archives in the project. |
check
|
All verification tasks in the project, including test . Some plugins add
additional verification tasks to the project.
|
Task |
Performs all verification tasks in the project. |
build
|
check and assemble
|
Task |
Performs a full build of the project. |
buildNeeded
|
build and build tasks in all project lib dependencies of the
testRuntime configuration.
|
Task |
Performs a full build of the project and all projects it depends on. |
buildDependents
|
build and build tasks in all projects with a project lib
dependency on this project in a testRuntime configuration.
|
Task |
Performs a full build of the project and all projects which depend on it. |
build
|
The tasks which produce the artifacts in configuration ConfigurationName .
|
Task |
Assembles the artifacts in the specified configuration. |
upload
|
The tasks which uploads the artifacts in configuration ConfigurationName .
|
Upload |
Assembles and uploads the artifacts in the specified configuration. |
The following diagram shows the relationships between these tasks.
The Java plugin assumes the project layout shown below. None of these directories need exist or have anything in them. The Java plugin will compile whatever it finds, and handles anything which is missing.
Table 20.4. Java plugin - default project layout
Directory | Meaning |
src/main/java
|
Production Java source |
src/main/resources
|
Production resources |
src/test/java
|
Test Java source |
src/test/resources
|
Test resources |
src/
|
Java source for the given source set |
src/
|
Resources for the given source set |
You configure the project layout by configuring the appropriate source set. This is discussed in more detail in the following sections. Here is a brief example which changes the main Java and resource source directories.
Example 20.2. Custom Java source layout
build.gradle
sourceSets { main { java { srcDir 'src/java' } resources { srcDir 'src/resources' } } }
The Java plugin adds a number of dependency configurations to your project, as shown below. It assigns
those configurations to tasks such as compileJava
and test
.
To learn more about configurations see Section 34.3.1, “Configurations” and
Section 35.2, “Artifacts and configurations”.
Table 20.5. Java plugin - dependency configurations
Name | Extends | Used by tasks | Meaning |
compile | - | compileJava | Compile time dependencies |
runtime | compile | - | Runtime dependencies |
testCompile | compile | compileTestJava | Additional dependencies for compiling tests. |
testRuntime | runtime, testCompile | test | Additional dependencies for running tests only. |
archives | - | uploadArchives | Artifacts (e.g. jars) produced by this project. |
default | runtime, archives | - | Artifacts produced and dependencies required by this project.
|
The Java plugin adds a number of convention properties to the project, shown below. You can use these properties in your build script as though they were properties of the project object (see Section 18.2, “Using the convention object”).
Table 20.6. Java plugin - directory properties
Property name | Type | Default value | Description |
reportsDirName
|
String
|
reports
|
The name of the directory to generate reports into, relative to the build directory. |
reportsDir
|
File (read-only)
|
|
The directory to generate reports into. |
testResultsDirName
|
String
|
test-results
|
The name of the directory to generate test result .xml files into, relative to the build directory. |
testResultsDir
|
File (read-only)
|
|
The directory to generate test result .xml files into. |
testReportDirName
|
String
|
tests
|
The name of the directory to generate the test report into, relative to the reports directory. |
testReportDir
|
File (read-only)
|
|
The directory to generate the test report into. |
libsDirName
|
String
|
libs
|
The name of the directory to generate libraries into, relative to the build directory. |
libsDir
|
File (read-only)
|
|
The directory to generate libraries into. |
distsDirName
|
String
|
distributions
|
The name of the directory to generate distributions into, relative to the build directory. |
distsDir
|
File (read-only)
|
|
The directory to generate distributions into. |
docsDirName
|
String
|
docs
|
The name of the directory to generate documentation into, relative to the build directory. |
docsDir
|
File (read-only)
|
|
The directory to generate documentation into. |
dependencyCacheDirName
|
String
|
dependency-cache
|
The name of the directory to use to cache source dependency information, relative to the build directory. |
dependencyCacheDir
|
File (read-only)
|
|
The directory to use to cache source dependency information. |
Table 20.7. Java plugin - other properties
Property name | Type | Default value | Description |
sourceSets
|
SourceSetContainer (read-only) |
Not null | Contains the project's source sets. |
sourceCompatibility
|
JavaVersion . Can also set using a String or a Number, eg
'1.5' or 1.5 .
|
1.5
|
Java version compatibility to use when compiling Java source. |
targetCompatibility
|
JavaVersion . Can also set using a String or Number, eg
'1.5' or 1.5 .
|
|
Java version to generate classes for. |
archivesBaseName
|
String
|
|
The basename to use for archives, such as JAR or ZIP files. |
manifest
|
Manifest |
an empty manifest | The manifest to include in all JAR files. |
metaInf
|
List
|
[] |
A set of file collections which specify the files to
include in the META-INF directory or all JAR files. |
These properties are provided by convention objects of type JavaPluginConvention
,
BasePluginConvention
and
ReportingBasePluginConvention
.
You can access the source sets of a project using the sourceSets
property. This
is a container for the project's source sets, of type SourceSetContainer
.
There is also a sourceSets()
method, which you can pass a closure to which configures the
source set container. The source set container works pretty much the same way as other containers, such
as tasks
.
Example 20.3. Accessing a source set
build.gradle
// Various ways to access the main source set println sourceSets.main.classesDir println sourceSets['main'].classesDir sourceSets { println main.classesDir } sourceSets { main { println classesDir } } // Iterate over the source sets sourceSets.each {SourceSet set -> println set.name }
To configure an existing source set, you simply use one of the above access methods to set the properties of the source set. The properties are described below. Here is an example which configures the main Java and resources directories:
Example 20.4. Configuring the source directories of a source set
build.gradle
sourceSets { main { java { srcDir 'src/java' } resources { srcDir 'src/resources' } } }
To define a new source set, you simply reference it in the sourceSets { }
block.
When you define a source set, the Java plugin adds a number of tasks which assemble the classes for the
source set, as shown in Table 20.2, “Java plugin - source set tasks”. For example, if you add a source set called
intTest
, the Java plugin adds compileIntTestJava
, processIntTestResources
and intTestClasses
tasks.
The following table lists some of the important properties of a source set.
You can find more details in the API documentation for SourceSet
.
Table 20.8. Java plugin - source set properties
Property name | Type | Default value | Description |
name
|
String (read-only)
|
Not null | The name of the source set, used to identify it. |
classesDir
|
File
|
|
The directory to generate the classes of this source set into. |
compileClasspath
|
FileCollection
|
compile Configuration.
|
The classpath to use when compiling the source files of this source set. |
runtimeClasspath
|
FileCollection
|
classesDir + runtime Configuration.
|
The classpath to use when executing the classes of this source set. |
java
|
SourceDirectorySet (read-only)
|
Not null |
The Java source files of this source set. Contains only .java files
found in the Java source directories, and excludes all other files.
|
java.srcDirs
|
Set<File> . Can set using anything described in Section 15.5, “Specifying a set of input files”.
|
[
|
The source directories containing the Java source files of this source set. |
resources
|
SourceDirectorySet (read-only)
|
Not null |
The resources of this source set. Contains only resources, and excludes any
.java files found in the resource source directories. Other plugins,
such as the Groovy plugin, exclude additional types of files from this collection.
|
resources.srcDirs
|
Set<File> . Can set using anything described in Section 15.5, “Specifying a set of input files”.
|
[
|
The source directories containing the resources of this source set. |
allJava
|
FileTree (read-only)
|
java
|
All .java files of this source set. Some plugins, such as the Groovy plugin,
add additional Java source files to this collection.
|
allSource
|
FileTree (read-only)
|
resources + java
|
All source files of this source set. This include all resource files and all Java source files. Some plugins, such as the Groovy plugin, add additional source files to this collection. |
Using dependency configurations to define the source set classpath:
Example 20.6. Defining the classpath of a source set
build.gradle
configurations { intTestCompile { extendsFrom compile } intTestRuntime { extendsFrom intTestCompile, runtime } } sourceSets { intTest { compileClasspath = sourceSets.main.classes + configurations.intTestCompile runtimeClasspath = classes + sourceSets.main.classes + configurations.intTestRuntime } }
Adding a JAR containing the classes of a source set:
Example 20.7. Assembling a JAR for a source set
build.gradle
task intTestJar(type: Jar) { from sourceSets.intTest.classes }
Generating Javadoc for a source set:
Example 20.8. Generating the Javadoc for a source set
build.gradle
task intTestJavadoc(type: Javadoc) { source sourceSets.intTest.allJava }
Adding a test suite to run the tests in a source set:
Example 20.9. Running tests in a source set
build.gradle
task intTest(type: Test) { testClassesDir = sourceSets.intTest.classesDir classpath = sourceSets.intTest.runtimeClasspath }
The javadoc
task is an instance of Javadoc
.
It supports the core javadoc options and the options of the standard doclet described in the
reference documentation
of the Javadoc executable.
For a complete list of supported Javadoc options consult the API documentation of the following classes:
CoreJavadocOptions
and StandardJavadocDocletOptions
.
Table 20.9. Java plugin - Javadoc properties
Task Property | Type | Default Value |
classpath
|
FileCollection |
sourceSets.main.classes + sourceSets.main.compileClasspath |
source |
FileTree . Can set using anything described in Section 15.5, “Specifying a set of input files”. |
sourceSets.main.allJava |
destinationDir
|
File |
|
title
|
String |
The name and version of the project |
The clean
task is an instance of Delete
. It
simply removes the directory denoted by its dir
property.
Table 20.10. Java plugin - Clean properties
Task Property | Type | Default Value |
dir
|
File |
|
The Java plugin uses the Copy
task for resource handling. It adds an
instance for each source set in the project. You can find out more about the copy task in
Section 15.6, “Copying files”.
Table 20.11. Java plugin - ProcessResources properties
Task Property | Type | Default Value |
srcDirs
|
Object . Can set using anything described in Section 15.5, “Specifying a set of input files”. |
|
destinationDir
|
File . Can set using anything described in Section 15.1, “Locating files”. |
|
The Java plugin adds a Compile
instance for each
source set in the project. The compile task delegates to Ant's javac task to do the compile. You can set most
of the properties of the Ant javac task.
Table 20.12. Java plugin - Compile properties
Task Property | Type | Default Value |
classpath
|
FileCollection |
|
source
|
FileTree . Can set using anything described in Section 15.5, “Specifying a set of input files”. |
|
destinationDir
|
File . |
|
The test
task is an instance of Test
.
It automatically detects and executes all unit tests in the test
source set.
It also generates a report once test execution is complete. JUnit and TestNG are both supported.
Have a look at Test
for the complete API.
Tests are executed in a separate isolated JVM. The Test
task's
API allows you some control over how this happens.
There are a number of properties which control how the test process is launched. This includes
things such as system properties, JVM arguments, and the Java executable to use. The task also provides a
debug
property, which when set to true, starts the test process in debug mode,
suspended and listening on port 5005. This makes it very easy to debug your tests. You may also enable
this using a system property as specified below.
You can specify whether or not to execute your tests in parallel. Gradle provides parallel test execution
by running multiple test processes concurrently. Each test process executes only a single test at a time, so you
generally don't need to do anything special to your tests to take advantage of this.
The maxParallelForks
property specifies the maximum number of test processes to run
at any given time. The default is 1, that is, do not execute the tests in parallel.
The test process sets the org.gradle.test.worker
system property to a unique
identifier for that test process, which you can use, for example, in files names or other
resource identifiers.
You can specify that test processes should be restarted after it has executed a certain number of
test classes. This can be a useful alternative to giving your test process a very large
heap.
The forkEvery
property specifies the
maximum number of test classes to execute in a test process. The default is to execute an unlimited number
of tests in each test process.
The task has an ignoreFailures
property to control the behavior when tests fail.
Test always executes every test that it detects. It stops the build afterwards if ignoreFailures
is false and there are failing tests. The default value of ignoreFailures
is false.
There are two system properties that can affect test execution. Both of these are based off of the name of the test task with a suffix.
Setting a system property of taskName.single
= testNamePattern
will only execute tests that match the specified testNamePattern
.
The taskName
can be a full multi-project path like ":sub1:sub2:test"
or just the task name. The testNamePattern
will be used to form an include
pattern of "**/testNamePattern*.class".
If no tests with this pattern can be found an exception is thrown. This is to shield you from false security.
If tests of more then one subproject are executed, the pattern is applied to each subproject. An exception
is thrown if no tests can be found for a particular subproject. In such a case you can use the path notation of the
pattern, so that the pattern is applied only to the test task of a specific subproject. Alternatively you can specify the fully
qualified task name to be executed. You can also specify multiple patterns. Examples:
gradle -Dtest.single=ThisUniquelyNamedTest test
gradle -Dtest.single=a/b/ test
gradle -DintegTest.single=*IntegrationTest integTest
gradle -Dtest.single=:proj1:test:Customer build
gradle -DintegTest.single=c/d/ :proj1:integTest
Setting a system property of taskName.debug
will run the tests in debug mode,
suspended and listening on port 5005. For example:
gradle test -Dtest.single=ThisUniquelyNamedTest -Dtest.debug
The Test
task detects which classes are test classes by inspecting the compiled test classes.
By default it scans all .class
files. You can set custom includes / excludes, only those
classes will be scanned. Depending on the test framework used (JUnit / TestNG) the test class detection
uses different criteria.
When using JUnit, we scan for both JUnit 3 and 4 test classes. If any of the following criteria match, the class is considered to be a JUnit test class:
Class or a super class extends TestCase
or GroovyTestCase
Class or a super class is annotated with @RunWith
Class or a super class contain a method annotated with @Test
When using TestNG, we scan for methods annotated with @Test
.
Note that abstract classes are not executed. Gradle also scan up the inheritance tree into jar files on the test classpath.
In case you don't want to use the test class detection, you can disable it by setting
scanForTestClasses
to false. This will make the test task only use the includes /
excludes to find test classes.
If scanForTestClasses
is disabled and no include or exclude patterns are specified, the
respective defaults are used. For include this is "**/*Tests.class", "**/*Test.class"
and the for exclude it is "**/Abstract*.class"
.
Table 20.13. Java plugin - test properties
Task Property | Type | Default Value |
testClassesDir |
File |
sourceSets.test.classesDir |
classpath |
FileCollection |
sourceSets.test.runtimeClasspath |
testResultsDir |
File |
testResultsDir |
testReportDir |
File |
testReportDir |
testSrcDirs |
List<File> |
sourceSets.test.java.srcDirs |
The jar
task creates a JAR file containing the class files and resources of the
project. The JAR file is declared as an artifact in the archives
dependency
configuration. This means that the JAR is available in the classpath of a dependent project. If you upload
your project into a repository, this JAR is declared as part of the dependency descriptor. You can learn
more about how to work with archives in Section 15.8, “Creating archives” and artifact configurations in
Chapter 35, Artifact Management.
Each jar or war object has a manifest
property with a separate instance of Manifest
.
When the archive is generated, a corresponding MANIFEST.MF
file is written into the
archive.
Example 20.10. Customization of MANIFEST.MF
build.gradle
jar { manifest { attributes("Implementation-Title": "Gradle", "Implementation-Version": version) } }
You can create stand alone instances of a Manifest
. You can use that for example,
to share manifest information between jars.
Example 20.11. Creating a manifest object.
build.gradle
sharedManifest = manifest { attributes("Implementation-Title": "Gradle", "Implementation-Version": version) } task fooJar(type: Jar) { manifest = project.manifest { from sharedManifest } }
You can merge other manifests into any Manifest
object. The other manifests might
be either described by a file path or, like in the example above, by a reference to another Manifest
object.
Example 20.12. Separate MANIFEST.MF for a particular archive
build.gradle
task barJar(type: Jar) { manifest { attributes key1: 'value1' from sharedManifest, 'src/config/basemanifest.txt' from('src/config/javabasemanifest.txt', 'src/config/libbasemanifest.txt') { eachEntry { details -> if (details.baseValue != details.mergeValue) { details.value = baseValue } if (details.key == 'foo') { details.exclude() } } } } }
Manifest are merged in the order they are declared by the from
statement. If
the based manifest and the merged manifest both define values for the same key, the merged manifest wins by default.
You can fully customize the merge behavior behavior by adding eachEntry
actions in which
you have access to a ManifestMergeDetails
instance for each entry
of the resulting manifest. The merge is not immediately triggered by the from statement. It is done lazily,
either when generating the jar, or by calling writeTo
or effectiveManifest
You can easily write a manifest to disk.
Example 20.13. Separate MANIFEST.MF for a particular archive
build.gradle
jar.manifest.writeTo("$buildDir/mymanifest.mf")
How to upload your archives is described in Chapter 35, Artifact Management.
The Groovy plugin extends the Java plugin to add support for Groovy projects. It can deal with Groovy-only projects and with mixed Java/Groovy projects. It can even deal with Java-only projects. [7] The Groovy plugin supports joint compilation of Java and Groovy. This means that your project can contain Groovy classes which use Java classes, and vice versa.
To use the Groovy plugin, include in your build script:
The Groovy plugin adds the following tasks to the project.
Table 21.1. Groovy plugin - tasks
Task name | Depends on | Type | Description |
compileGroovy |
compileJava |
GroovyCompile |
Compiles production Groovy source files using groovyc. |
compileTestGroovy |
compileTestJava |
GroovyCompile |
Compiles test Groovy source files using groovyc. |
compile |
compile |
GroovyCompile |
Compiles the given source set's Groovy source files using groovyc. |
groovydoc |
- | Groovydoc |
Generates API documentation for the production Groovy source files using groovydoc. |
The Groovy plugin adds the following dependencies to tasks added by the Java plugin.
Table 21.2. Groovy plugin - additional task dependencies
Task name | Depends on |
classes | compileGroovy |
testClasses | compileTestGroovy |
sourceSet Classes |
compileSourceSet Groovy |
The Groovy plugin assumes the project layout shown in Table 21.3, “Groovy plugin - project layout”. All the Groovy source directories can contain Groovy and Java code. The Java source directories may only contain Java source code. [8] None of these directories need exist or have anything in them. The Groovy plugin will compile whatever it finds, and handles anything which is missing.
Table 21.3. Groovy plugin - project layout
Directory | Meaning |
src/main/java
|
Production Java source |
src/main/resources
|
Production resources |
src/main/groovy
|
Production Groovy source. May also contain Java source for joint compilation. |
src/test/java
|
Test Java source |
src/test/resources
|
Test resources |
src/test/groovy
|
Test Groovy source. May also contain Java source for joint compilation. |
src/
|
Java source for the given source set |
src/
|
Resources for the given source set |
src/
|
Groovy source for the given source set. May also contain Java source for joint compilation. |
The Groovy plugin adds a dependency configuration called groovy
.
Gradle is written in Groovy and allows you to write your build scripts in Groovy. But this is an internal
aspect of Gradle which is strictly separated from building Groovy projects. You are free to choose the Groovy
version your project should be build with. This Groovy version is not just used for compiling your code and
running your tests. The groovyc
compiler and the the groovydoc
tool are also taken from the Groovy version you provide. As usual, with freedom comes responsibility ;). You are
not just free to choose a Groovy version, you have to provide one. Gradle expects that the groovy libraries are
assigned to the groovy
dependency configuration. Here is an example using the public Maven
repository:
Example 21.3. Configuration of Groovy plugin
build.gradle
repositories { mavenCentral() } dependencies { groovy group: 'org.codehaus.groovy', name: 'groovy', version: '1.7.10' }
And here is an example using the Groovy JARs checked into the lib
directory of the source
tree:
Example 21.4. Configuration of Groovy plugin
build.gradle
repositories { flatDir(dirs: file('lib')) } dependencies { groovy module(':groovy:1.6.0') { dependency('asm:asm-all:2.2.3') dependency('antlr:antlr:2.7.7') dependency('commons-cli:commons-cli:1.2') module(':ant:1.7.0') { dependencies(':ant-junit:1.7.0:jar', ':ant-launcher:1.7.0') } } }
The Groovy plugin adds the following convention properties to each source set in the project. You can use these properties in your build script as though they were properties of the source set object (see Section 18.2, “Using the convention object”).
Table 21.4. Groovy plugin - source set properties
Property name | Type | Default value | Description |
groovy
|
SourceDirectorySet (read-only)
|
Not null |
The Groovy source files of this source set. Contains all .groovy and
.java files found in the Groovy source directories, and excludes all other
types of files.
|
groovy.srcDirs
|
Set<File> . Can set using anything described in Section 15.5, “Specifying a set of input files”.
|
[
|
The source directories containing the Groovy source files of this source set. May also contain Java source files for joint compilation. |
allGroovy
|
FileTree (read-only)
|
Not null |
All Groovy source files of this source set. Contains only the .groovy files
found in the Groovy source directories.
|
These properties are provided by a convention object of type GroovySourceSet
.
The Groovy plugin also modifies some source set properties:
Table 21.5. Groovy plugin - source set properties
Property name | Change |
allJava
|
Adds all .java files found in the Groovy source directories. |
allSource
|
Adds all source files found in the Groovy source directories. |
The Groovy plugin adds a GroovyCompile
instance for
each source set in the project. The task type extends the Compile
task (see Section 20.11, “CompileJava”). The compile task delegates to the Ant Groovyc task to do the
compile. Via the compile task you can set most of the properties of Ants Groovyc task.
Table 21.6. Groovy plugin - CompileGroovy properties
Task Property | Type | Default Value |
classpath
|
FileCollection |
|
source
|
FileTree . Can set using anything described in Section 15.5, “Specifying a set of input files”. |
|
destinationDir
|
File . |
|
groovyClasspath
|
FileCollection |
groovy configuration |
[7] We don't recommend this, as the Groovy plugin uses the Groovyc
Ant task to compile the sources. For pure Java projects you might rather stick with
javac
. In particular as you would have to supply a groovy jar for doing this.
[8] We are using the same conventions as introduced by Russel Winders Gant tool (http://gant.codehaus.org).
The Scala plugin extends the Java plugin to add support for Scala projects. It can deal with Scala-only projects and with mixed Java/Scala projects. It can even deal with Java-only projects. The Scala plugin supports joint compilation of Java and Scala source. This means your project can contain Scala classes which use Java classes, and vice versa.
To use the Scala plugin, include in your build script:
The Scala plugin adds the following tasks to the project.
Table 22.1. Scala plugin - tasks
Task name | Depends on | Type | Description |
compileScala |
compileJava |
ScalaCompile |
Compiles production Scala source files using scalac. |
compileTestScala |
compileTestJava |
ScalaCompile |
Compiles test Scala source files using scalac. |
compile |
compile |
ScalaCompile |
Compiles the given source set's Scala source files using scalac. |
scaladoc |
- | ScalaDoc |
Generates API documentation for the production Scala source files using scaladoc. |
The Scala plugin adds the following dependencies to tasks added by the Java plugin.
Table 22.2. Scala plugin - additional task dependencies
Task name | Depends on |
classes
|
compileScala
|
testClasses
|
compileTestScala
|
|
compile
|
The Scala plugin assumes the project layout shown below. All the Scala source directories can contain Scala and Java code. The Java source directories may only contain Java source code. None of these directories need exist or have anything in them. The Scala plugin will compile whatever it finds, and handles anything which is missing.
Table 22.3. Scala plugin - project layout
Directory | Meaning |
src/main/java
|
Production Java source |
src/main/resources
|
Production resources |
src/main/scala
|
Production Scala source. May also contain Java source for joint compilation. |
src/test/java
|
Test Java source |
src/test/resources
|
Test resources |
src/test/scala
|
Test Scala source. May also contain Java source for joint compilation. |
src/
|
Java source for the given source set |
src/
|
Resources for the given source set |
src/
|
Scala source for the given source set. May also contain Java source for joint compilation. |
The Scala plugin adds a scalaTools
configuration, which it uses to locate the Scala
tools, such as scalac, to use. You must specify the version of Scala to use. Below is an example.
Example 22.3. Declaring the Scala version to use
build.gradle
repositories { mavenCentral() } dependencies { // Libraries needed to run the scala tools scalaTools 'org.scala-lang:scala-compiler:2.8.1' scalaTools 'org.scala-lang:scala-library:2.8.1' // Libraries needed for scala api compile 'org.scala-lang:scala-library:2.8.1' }
The Scala plugin adds the following convention properties to each source set in the project. You can use these properties in your build script as though they were properties of the source set object (see Section 18.2, “Using the convention object”).
Table 22.4. Scala plugin - source set properties
Property name | Type | Default value | Description |
scala
|
SourceDirectorySet (read-only)
|
Not null |
The Scala source files of this source set. Contains all .scala and
.java files found in the Scala source directories, and excludes all other
types of files.
|
scala.srcDirs
|
Set<File> . Can set using anything described in Section 15.5, “Specifying a set of input files”.
|
[
|
The source directories containing the Scala source files of this source set. May also contain Java source files for joint compilation. |
allScala
|
FileTree (read-only)
|
Not null |
All Scala source files of this source set. Contains only the .scala files
found in the Scala source directories.
|
These convention properties are provided by a convention object of type ScalaSourceSet
.
The Scala plugin also modifies some source set properties:
Table 22.5. Scala plugin - source set properties
Property name | Change |
allJava
|
Adds all .java files found in the Scala source directories. |
allSource
|
Adds all source files found in the Scala source directories. |
The Scala plugin includes support for fsc,
the Fast Scala Compiler. fsc
runs in a separate daemon process and can speed up
compilation significantly.
Example 22.4. Enabling the Fast Scala Compiler
build.gradle
compileScala { scalaCompileOptions.useCompileDaemon = true // optionally specify host and port of the daemon: scalaCompileOptions.daemonServer = "localhost:4243" }
Note that fsc
expects to be restarted whenever the contents of its
compile class path change. (It does detect changes to the compile class path itself.) This makes it
less suitable for multi-project builds.
The War plugin extends the Java plugin to add support for assembling web application WAR files. It disables the default JAR archive generation of the Java plugin and adds a default WAR archive task.
To use the War plugin, include in your build script:
The War plugin adds the following tasks to the project.
Table 23.1. War plugin - tasks
Task name | Depends on | Type | Description |
war
|
compile
|
War |
Assembles the application WAR file. |
The War plugin adds the following dependencies to tasks added by the Java plugin.
Table 23.2. War plugin - additional task dependencies
Task name | Depends on |
assemble | war |
Table 23.3. War plugin - project layout
Directory | Meaning |
src/main/webapp
|
Web application sources |
The War plugin adds two dependency configurations: providedCompile
and
providedRuntime
. Those configurations have the same scope as the respective
compile
and runtime
configurations, except that they are not added to
the WAR archive. It is important to note that those provided
configurations work
transitively. Let's say you add commons-httpclient:commons-httpclient:3.0
to any of the
provided configurations. This dependency has a dependency on commons-codec
.
This means neither httpclient
nor commons-codec
is added to your
WAR, even if commons-codec
were an explicit dependency of your compile
configuration. If you don't want this transitive behavior, simply declare your provided
dependencies like commons-httpclient:commons-httpclient:3.0@jar
.
Table 23.4. War plugin - directory properties
Property name | Type | Default value | Description |
webAppDirName
|
String
|
src/main/webapp
|
The name of the web application source directory, relative to the project directory. |
webAppDir
|
File (read-only)
|
|
The web application source directory. |
These properties are provided by a WarPluginConvention
convention object.
The default behavior of the War task is to copy the content of src/main/webapp
to the root of the archive. Your webapp
directory may of course contain a
WEB-INF
sub-directory, which again may contain a web.xml
file.
Your compiled classes are compiled to WEB-INF/classes
. All the dependencies of the
runtime
[9]
configuration are copied to WEB-INF/lib
.
Have also a look at War
.
Here is an example with the most important customization options:
Example 23.2. Customization of war plugin
build.gradle
import org.apache.commons.httpclient.HttpClient import org.apache.commons.httpclient.methods.GetMethod group = 'gradle' version = '1.0' apply plugin: 'war' apply plugin: 'jetty' configurations { moreLibs } repositories { flatDir(dirs: "$projectDir/lib") mavenCentral() } dependencies { compile module(":compile:1.0") { dependency ":compile-transitive-1.0@jar" dependency ":providedCompile-transitive:1.0@jar" } providedCompile "javax.servlet:servlet-api:2.5" providedCompile module(":providedCompile:1.0") { dependency ":providedCompile-transitive:1.0@jar" } runtime ":runtime:1.0" providedRuntime ":providedRuntime:1.0@jar" testCompile "junit:junit:4.8.2" moreLibs ":otherLib:1.0" } war { from 'src/rootContent' // adds a file-set to the root of the archive webInf { from 'src/additionalWebInf' } // adds a file-set to the WEB-INF dir. classpath fileTree('additionalLibs') // adds a file-set to the WEB-INF/lib dir. classpath configurations.moreLibs // adds a configuration to the WEB-INF/lib dir. webXml = file('src/someWeb.xml') // copies a file to WEB-INF/web.xml } jar.enabled = true [jettyRun, jettyRunWar]*.daemon = true stopKey = 'foo' stopPort = 9451 httpPort = 8163 task runTest(dependsOn: jettyRun) << { callServlet() } task runWarTest(dependsOn: jettyRunWar) << { callServlet() } private void callServlet() { HttpClient client = new HttpClient() GetMethod method = new GetMethod("http://localhost:$httpPort/customised/hello") client.executeMethod(method) new File(buildDir, "servlet-out.txt").write(method.getResponseBodyAsString()) jettyStop.execute() }
Of course one can configure the different file-sets with a closure to define excludes and includes.
If you want to enable the generation of the default jar archive additional to the war archive just type:
The Jetty plugin extends the War plugin to add tasks which allow you to deploy your web application to a Jetty web container embedded in the build.
To use the Jetty plugin, include in your build script:
The Jetty plugin defines the following tasks:
Table 24.1. Jetty plugin - tasks
Task name | Depends on | Type | Description |
jettyRun
|
compile
|
JettyRun |
Starts a Jetty instance and deploys the exploded web application to it. |
jettyRunWar
|
war
|
JettyRunWar |
Starts a Jetty instance and deploys the WAR to it. |
jettyStop
|
- | JettyStop |
Stops the Jetty instance. |
The Jetty plugin defines the following convention properties:
Table 24.2. Jetty plugin - properties
Property name | Type | Default value | Description |
httpPort
|
Integer
|
8080
|
The TCP port which Jetty should listen for HTTP requests on. |
stopPort
|
Integer
|
null
|
The TCP port which Jetty should listen for admin requests on. |
stopKey
|
String
|
null
|
The key to pass to Jetty when requesting it to stop. |
These properties are provided by a JettyPluginConvention
convention object.
The code quality plugin adds tasks which perform code quality checks and generate reports from these checks. The following tools are supported:
To use the code quality plugin, include in your build script:
When used with the Java plugin, the code quality plugin adds the following tasks to the project:
Table 25.1. Code quality plugin - Java tasks
Task name | Depends on | Type | Description |
checkstyleMain
|
- | Checkstyle |
Runs Checkstyle against the production Java source files. |
checkstyleTest
|
compile |
Checkstyle |
Runs Checkstyle against the test Java source files. |
checkstyle
|
- | Checkstyle |
Runs Checkstyle against the given source set's Java source files. |
When used with the Groovy plugin, the code quality plugin adds the following tasks to the project:
Table 25.2. Code quality plugin - tasks
The Code quality plugin adds the following dependencies to tasks added by the Java plugin.
Table 25.3. Code quality plugin - additional task dependencies
Task name | Depends on |
check | All Checkstyle and CodeNarc tasks, including checkstyleMain ,
checkstyleTest ,
codenarcMain and
codenarcTest
|
The code quality plugin expects the following project layout:
Table 25.4. Code quality plugin - project layout
File | Meaning |
config/checkstyle/checkstyle.xml
|
Checkstyle configuration file |
config/codenarc/codenarc.xml
|
CodeNarc configuration file |
When used with the Java plugin, the code quality plugin adds the following convention properties to the project:
Table 25.5. Code quality plugin - convention properties
Property name | Type | Default value | Description |
checkstyleConfigFileName
|
String
|
config/checkstyle/checkstyle.xml
|
The location of the Checkstyle configuration file, relative to the project directory. |
checkstyleConfigFile
|
File (read-only)
|
|
The Checkstyle configuration file. |
checkstyleResultsDirName
|
String
|
checkstyle
|
The name of the directory to generate Checkstyle results into, relative to the build directory. |
checkstyleResultsDir
|
File (read-only)
|
|
The directory to generate Checkstyle results into. |
checkstyleProperties
|
Map
|
[:]
|
The properties to use when loading the Checkstyle configuration. |
These convention properties are provided by a convention object of type
JavaCodeQualityPluginConvention
.
When used with the Groovy plugin, the code quality plugin adds the following convention properties to the project:
Table 25.6. Code quality plugin - convention properties
Property name | Type | Default value | Description |
codeNarcConfigFileName
|
String
|
config/codenarc/codenarc.xml
|
The location of the CodeNarc configuration file, relative to the project directory. |
codeNarcConfigFile
|
File (read-only)
|
|
The CodeNarc configuration file. |
codeNarcReportsDirName
|
String
|
codenarc
|
The name of the directory to generate CodeNarc reports into, relative to the reports directory. |
codeNarcReportsDir
|
File (read-only)
|
|
The directory to generate CodeNarc reports into. |
These convention properties are provided by a convention object of type
GroovyCodeQualityPluginConvention
.
The Sonar plugin provides integration with Sonar,
a web-based platform for monitoring code quality. The plugin adds a sonar
task
to the project, which analyzes the project's source code and stores the results in Sonar's database.
The sonar
task is a standalone task that needs to be executed explicitly. By default,
it gets configured to analyze the Java code in the main source set. In a typical setup, the task would
be run once per day on a build server.
Only projects which have the Java plugin applied (possibly by way of another plugin) are affected by the
Sonar plugin. Other projects can still declare a task of type Sonar
and configure it manually.
At a minimum, the Sonar plugin has to be applied to the project.
Typically, it is also necessary to configure connection settings for the Sonar server and database.
Example 26.2. Configuring connection settings
build.gradle
sonar { serverUrl = "http://my.server.com" globalProperty "sonar.jdbc.url", "jdbc:mysql://my.server.com/sonar" globalProperty "sonar.jdbc.driverClassName", "com.mysql.jdbc.Driver" globalProperty "sonar.jdbc.username", "myusername" globalProperty "sonar.jdbc.password", "mypassword" }
For a complete documentation of all Sonar-specific configuration properties, see the Sonar documentation.
.The Sonar plugin adds the following tasks to the project.
Table 26.1. Sonar plugin - tasks
Task name | Depends on | Type | Description |
sonar |
- | Sonar |
Analyzes the project's source code and stores results in Sonar's database. |
The OSGi plugin provides a factory method to create an
OsgiManifest
object. OsgiManifest
extends
Manifest
. To learn more
about generic manifest handling, see Section 20.13.1, “Manifest”. If the Java plugins is applied, the OSGi plugin
replaces the manifest object of the default jar with an OsgiManifest
object. The replaced manifest
is merged into the new one.
The OSGi plugin makes heavy use of Peter Kriens BND tool.
To use the OSGi plugin, include in your build script:
The OSGi plugin adds the following convention object: OsgiPluginConvention
The OSGi plugin adds the following methods. For more details, see the API documentation of the convention object.
Table 27.1. OSGi methods
Method | Return Type | Description |
osgiManifest() |
OsgiManifest
|
Returns an OsgiManifest object. |
osgiManifest(Closure cl) |
OsgiManifest
|
Returns an OsgiManifest object configured by the closure. |
The classes in the classes dir are analyzed regarding there package dependencies and the packages they expose.
Based on this the Import-Package and the Export-Package values of the
OSGi Manifest are calculated. If the classpath contains jars with an OSGi bundle, the bundle
information is used to specify version information for the Import-Package
value. Beside the explicit properties of the OsgiManifest
object you can add instructions.
Example 27.2. Configuration of OSGi MANIFEST.MF file
build.gradle
jar { manifest { // the manifest of the default jar is of type OsgiManifest name = 'overwrittenSpecialOsgiName' instruction 'Private-Package', 'org.mycomp.package1', 'org.mycomp.package2' instruction 'Bundle-Vendor', 'MyCompany' instruction 'Bundle-Description', 'Platform2: Metrics 2 Measures Framework' instruction 'Bundle-DocURL', 'http://www.mycompany.com' } } task fooJar(type: Jar) { manifest = osgiManifest { instruction 'Bundle-Vendor', 'MyCompany' } }
The first argument of the instruction call is the key of the property. The other arguments form the value.
They are joined by Gradle with the ,
separator. To learn more about the available
instructions have a look at the BND tool.
The Eclipse plugin generates files that are used by the Eclipse IDE, thus making it possible to import the project into Eclipse ( - - ). Both external dependencies (including associated source and javadoc files) and project dependencies are considered.
What exactly the Eclipse plugin generates depends on which other plugins are used:
Table 28.1. Eclipse plugin behavior
Plugin | Description |
None | Generates minimal .project file. |
Java | Adds Java configuration to .project .
Generates .classpath and JDT settings file. |
Groovy | Adds Groovy configuration to .project file. |
Scala | Adds Scala support to .project file. |
War | Adds web application support to .project file.
Generates WTP settings files. |
One focus of the Eclipse plugin is to be open to customization. Each task provides a standardized set of hooks for adding and removing content from the generated files.
To use the Eclipse plugin, include this in your build script:
The Eclipse plugin adds a number of tasks to your projects. The main tasks that you will use
are the eclipse
andcleanEclipse
tasks.
The Eclipse plugin adds the tasks shown below to a project.
Table 28.2. Eclipse plugin - tasks
Task name | Depends on | Type | Description |
eclipse
|
eclipseProject , eclipseClasspath , eclipseJdt ,
eclipseWtpComponent , cleanEclipseWtpFacet |
Task |
Generates all Eclipse configuration files |
cleanEclipse
|
cleanEclipseProject , cleanEclipseClasspath , cleanEclipseJdt ,
cleanEclipseWtpComponent , cleanEclipseWtpFacet
|
Delete |
Removes all Eclipse configuration files |
cleanEclipseProject
|
-
|
Delete |
Generates the .project file. |
cleanEclipseClasspath
|
-
|
Delete |
Generates the .classpath file. |
cleanEclipseJdt
|
-
|
Delete |
Removes the .settings/org.eclipse.jdt.core.prefs file. |
cleanEclipseWtpComponent
|
-
|
Delete |
Removes the .settings/org.eclipse.wst.common.component file. |
cleanEclipseWtpFacet
|
-
|
Delete
|
Removes the .settings/org.eclipse.wst.common.component file.
|
eclipseProject
|
-
|
EclipseProject |
Generates the .project file. |
eclipseClasspath
|
-
|
EclipseClasspath |
Generates the .classpath file. |
eclipseJdt
|
-
|
EclipseJdt |
Generates the .settings/org.eclipse.jdt.core.prefs file. |
eclipseWtpComponent
|
-
|
EclipseWtpComponent |
Generates the .settings/org.eclipse.wst.common.component file. |
eclipseWtpFacet
|
-
|
EclipseWtpFacet
|
Generates the .settings/org.eclipse.wst.common.project.facet.core.xml file. |
Table 28.3. EclipseProject task
Property | Type | Default Value | Description |
projectName
|
String
|
project.name |
The name of the Eclipse project. Must not be null. |
comment
|
String
|
project.description |
A comment for the Eclipse project. |
referencedProjects
|
Set<String>
|
empty set | The referenced projects of the Eclipse project. |
natures
|
List<String>
|
The default is an empty set. Applying Java, Groovy, Scala or War plugin will add additional natures. | The natures of the Eclipse project. |
buildCommands
|
List<BuildCommand>
|
The default is an empty set. Applying Java, Groovy, Scala or War plugin will add additional build commands. | The build commands of the Eclipse project. |
links
|
Set<Link>
|
empty set | The links for the Eclipse project. |
Table 28.4. EclipseClasspath task
Property | Type | Default Value | Description |
sourceSets
|
Iterable<SourceSet> |
project.sourceSets
|
The source sets whose source directories are to be added to the Eclipse classpath. |
containers
|
Set<String>
|
empty set | The containers to be added to the Eclipse classpath. |
plusConfigurations
|
Set<Configuration>
|
[configurations.testRuntime] |
The configurations whose files are to be transformed into classpath entries. |
minusConfigurations
|
Set<Configuration>
|
empty set | The configurations whose files are to be excluded from the classpath entries. |
downloadSources
|
boolean
|
true
|
Whether to download sources for external dependencies. |
downloadJavadoc
|
boolean
|
false
|
Whether to download javadoc for external dependencies. |
variables
|
Map<String,File>
|
[:] |
If the beginning of the absolute path of a library matches a value of a variable, a variable entry is created. The matching part of the library path is replaced with the variable name. |
Table 28.5. EclipseWtpComponent task
Property | Type | Default Value | Description |
sourceDirs
|
Set<File> |
The source directories of sourceSets.main
|
The source sets whose source directories are to be added to the Eclipse classpath. |
deployName
|
String
|
project.name |
The deploy name to be used. |
plusConfigurations
|
Set<Configuration>
|
[configurations.testRuntime] |
The configurations whose files are to be transformed into classpath entries. |
minusConfigurations
|
Set<Configuration>
|
[configurations.providedRuntime] |
The configurations whose files are to be excluded from the classpath entries. |
variables
|
Map<String,File>
|
[:] |
If the beginning of the absolute path of a library matches a value of a variable, a variable entry is created. The matching part of the library path is replaced with the variable name. |
Table 28.6. EclipseWtpFacet task
Property | Type | Default Value | Description |
facets
|
List<Facet>
|
jst.java
and
jst.web
facet
|
The facets to be added as installed elements. |
All Eclipse tasks provide the same hooks and behavior for customizing the generated content.
The tasks recognize existing Eclipse files, and merge them with the generated content.
Sections of existing Eclipse files that are also the target of generated content will be amended or overwritten, depending on the particular section. The remaining sections will be left as-is.
To completely overwrite existing Eclipse files, execute a clean task together with its corresponding generation task,
for example gradle cleanEclipse eclipse
(in that order). If you want to make this
the default behavior, add eclipse.dependsOn(cleanEclipse)
to your build script. This makes it
unnecessary to execute the clean task explicitly.
Complete overwrite works equally well for individual files, for example by executinggradle cleanEclipseClasspath eclipseClasspath
.
The Eclipse plugin provides domain classes modeling the sections of the Eclipse files that are autogenerated by Gradle. The generation lifecycle is as follows:
beforeConfigured
hook is executedwhenConfigured
hook is executedwithXml
hook is executedThe following table lists the domain object used for each of the Eclipse task types:
Table 28.7. Task Hooks
Task type | beforeConfigured { arg -> } argument type |
whenConfigured { arg -> } argument type |
withXml { arg -> } argument type |
EclipseProject |
Project |
Project |
XmlProvider |
EclipseClasspath |
Classpath |
Classpath |
XmlProvider |
EclipseJdt |
Jdt |
Jdt |
XmlProvider |
EclipseWtpComponent |
WtpComponent |
WtpComponent |
XmlProvider |
EclipseWtpFacet |
WtpFacet |
WtpFacet |
XmlProvider |
A complete overwrite causes all existing content to be discarded,
thereby losing any changes made directly in the IDE. The beforeConfigured
hook makes it possible
to overwrite just certain parts of the existing content. The following example removes all existing dependencies
from the Classpath
domain object:
Example 28.2. Partial Overwrite for Classpath
build.gradle
eclipseClasspath { beforeConfigured { classpath -> classpath.entries.removeAll { entry -> entry.kind == 'lib' || entry.kind == 'var' } } }
The resulting .classpath
file will only contain Gradle-generated dependency entries, but
not any other dependency entries that may have been present in the original file. (In the case of dependency entries,
this is also the default behavior.) Other sections of the .classpath
file will be either left as-is or merged.
The same could be done for the natures in the .project
file:
Example 28.3. Partial Overwrite for Project
build.gradle
eclipseProject { beforeConfigured { project -> project.natures.clear() } }
The whenConfigured
hook allows to manipulate the fully populated domain objects. Often this is the
preferred way to customize Eclipse files. Here is how you would export all the dependencies of an Eclipse project:
Example 28.4. Export Dependencies
build.gradle
eclipseClasspath {
whenConfigured { classpath ->
classpath.entries.findAll { entry -> entry.kind == 'lib' }*.exported = false
}
}
The withXml
hook allows to manipulate the in-memory XML representation just before the file gets written to disk.
Although Groovy's XML support makes up for a lot, this approach is less convenient than manipulating the domain objects.
In return, you get total control over the generated file, including sections not modeled by the domain objects.
Example 28.5. Customizing the XML
build.gradle
eclipseWtpFacet { withXml { provider -> provider.asNode().fixed.find { it.@facet == 'jst.java' }.@facet = 'jst2.java' } }
The IDEA plugin generates files that are used by IntelliJ IDEA, thus making it possible to open the project from IDEA ( - ). Both external dependencies (including associated source and javadoc files) and project dependencies are considered.
What exactly the IDEA plugin generates depends on which other plugins are used:
Table 29.1. IDEA plugin behavior
Plugin | Description |
None | Generates an IDEA module file. Also generates an IDEA project and workspace file if the project is the root project. |
Java | Adds Java configuration to the module and project files. |
One focus of the IDEA plugin is to be open to customization. Each task provides a standardized set of hooks for adding and removing content from the generated files.
To use the IDEA plugin, include this in your build script:
The IDEA plugin adds a number of tasks to your project. The main tasks that you will use
are the idea
and cleanIdea
tasks.
The IDEA plugin adds the tasks shown below to a project.
Table 29.2. IDEA plugin - Tasks
Task name | Depends on | Type | Description |
idea
|
ideaProject , ideaModule , ideaWorkspace |
- |
Generates all IDEA configuration files |
cleanIdea
|
cleanIdeaProject , cleanIdeaModule , cleanIdeaWorkspace
|
Delete |
Removes all IDEA configuration files |
cleanIdeaProject
|
-
|
Delete |
Removes the IDEA project file |
cleanIdeaModule
|
-
|
Delete |
Removes the IDEA module file |
cleanIdeaWorkspace
|
-
|
Delete |
Removes the IDEA workspace file |
ideaProject
|
-
|
GenerateIdeaProject |
Generates the .ipr file. This task is only added to the root project. |
ideaModule
|
-
|
GenerateIdeaModule |
Generates the .iml file |
ideaWorkspace
|
-
|
GenerateIdeaWorkspace |
Generates the .iws file. This task is only added to the root project. |
Table 29.3. IdeaModule task
Property | Type | Default Value | Default Value with Java Plugin | Description |
moduleDir
|
File
|
projectDir |
projectDir |
The content root directory of the module. Must not be null. |
outputFile
|
File
|
|
- | The .iml file. Used to look for existing files and as the target for generation. Must not be null. |
inheritOutputDirs
|
Boolean
|
null | null | If null , the value in the existing or default module file is used (the default file uses
true ). If true , the module output directories will be located below the
project output directories. If false , the directories specified with the sourceDirs
and testSourceDirs properties are used. |
sourceDirs
|
Set<File>
|
empty set | The source directories of sourceSets.main |
The directories containing the production sources. Must not be null. |
testSourceDirs
|
Set<File>
|
empty set | The source directories of sourceSets.test |
The directories containing the test sources. Must not be null. |
excludeDirs
|
Set<File>
|
empty set | - | The directories to be excluded by IDEA. Must not be null. |
outputDir
|
File
|
null
|
null |
The IDEA output directory for the production sources. If null, no entry is created. |
testOutputDir
|
File
|
null
|
null |
The IDEA output directory for the test sources. If null, no entry is created. |
javaVersion
|
String
|
null
|
- | If null, the value of the existing or default .ipr file is used (the default file uses
inherited ). If set to inherited , the project SDK is used. Otherwise,
the SDK for the corresponding value of java version is used. |
downloadSources
|
boolean
|
true
|
- | Whether to download and add source Jars associated with the dependency Jars. |
downloadJavadoc
|
boolean
|
false
|
- | Whether to download and add javadoc Jars associated with the dependency Jars. |
scopes
|
Map
|
[:]
|
COMPILE(compile), RUNTIME(runtime - compile), TEST(testRuntime - runtime) | The keys of this map are the IDEA scopes. Each key points to another map that has two keys, plus and minus. The values of those keys are sets of Configuration objects. The files of the plus configurations are added minus the files from the minus configurations. |
variables
|
Map<String, File>
|
[:]
|
- | The variables to be used for replacing absolute paths in the .iml file. For example, you might add
a GRADLE_USER_HOME variable to point to the Gradle user home directory. |
Table 29.4. IdeaProject task
Property | Type | Default Value | Default Value with Java Plugin | Description |
subprojects
|
Set<Project>
|
rootProject.allprojects |
- | The subprojects that should be mapped to modules in the .ipr
file. The subprojects will only be mapped if the IDEA plugin has been
applied to them. |
outputFile
|
File
|
|
- | The .ipr file. Used to look for existing files and as the target for generation. Must not be null. |
javaVersion
|
String
|
1.6
|
- | The Java version used for defining the project SDK. |
wildcards
|
Set<String>
|
['!?*.java', '!?*.groovy']
|
- | The wildcard resource patterns. Must not be null. |
Table 29.5. IdeaWorkspace task
Property | Type | Default Value | Default Value with Java Plugin | Description |
outputFile
|
File
|
|
- | The .iws file. Used to look for existing files and as the target for generation. Must not be null. |
All IDEA tasks provide the same hooks and behavior for customizing the generated content.
However, the workspace file can effectively only be manipulated via the withXml
hook,
because its corresponding domain object is essentially empty.
The tasks recognize existing IDEA files, and merge them with the generated content.
Sections of existing IDEA files that are also the target of generated content will be amended or overwritten, depending on the particular section. The remaining sections will be left as-is.
To completely overwrite existing IDEA files, execute a clean task together with its corresponding generation task,
for example gradle cleanIdea idea
(in that order). If you want to make this
the default behavior, add idea.dependsOn(cleanIdea)
to your build script. This makes it
unnecessary to execute the clean task explicitly.
Complete overwrite works equally well for individual files, for example by executinggradle cleanIdeaModule ideaModule
.
The IDEA plugin provides domain classes modeling the sections of the IDEA files that are autogenerated by Gradle. The generation lifecycle is as follows:
beforeConfigured
hook is executedwhenConfigured
hook is executedwithXml
hook is executedThe following table lists the domain objects used for each of the IDEA task types:
Table 29.6. Task Hooks
Task type | beforeConfigured { arg -> } argument type |
whenConfigured { arg -> } argument type |
withXml { arg -> } argument type |
GenerateIdeaProject |
Project |
Project |
XmlProvider |
GenerateIdeaModule |
Module |
Module |
XmlProvider |
GenerateIdeaWorkspace |
Workspace |
Workspace |
XmlProvider |
A complete overwrite causes all existing content to be discarded,
thereby losing any changes made directly in the IDE. The beforeConfigured
hook makes it possible
to overwrite just certain parts of the existing content. The following example removes all existing dependencies
from the Module
domain object:
Example 29.2. Partial Overwrite for Module
build.gradle
ideaModule { beforeConfigured { module -> module.dependencies.clear() } }
The resulting module file will only contain Gradle-generated dependency entries, but
not any other dependency entries that may have been present in the original file. (In the case of dependency entries,
this is also the default behavior.) Other sections of the module file will be either left as-is or merged.
The same could be done for the module paths in the project file:
Example 29.3. Partial Overwrite for Project
build.gradle
ideaProject { beforeConfigured { project -> project.modulePaths.clear() } }
The whenConfigured
hook allows to manipulate the fully populated domain objects. Often this is the
preferred way to customize IDEA files. Here is how you would export all the dependencies of an IDEA module:
Example 29.4. Export Dependencies
build.gradle
ideaModule { whenConfigured { module -> module.dependencies*.exported = true } }
The withXml
hook allows to manipulate the in-memory XML representation just before the file gets written to disk.
Although Groovy's XML support makes up for a lot, this approach is less convenient than manipulating the domain objects.
In return, you get total control over the generated file, including sections not modeled by the domain objects.
Example 29.5. Customizing the XML
build.gradle
ideaProject { withXml { provider -> provider.node.component.find { it.@name == 'VcsDirectoryMappings' }.mapping.@vcs = 'Git' } }
The paths of the dependencies in the generated IDEA files are absolute. If you manually define a path variable pointing to the Gradle dependency cache, IDEA will automatically replace the absolute dependency paths with this path variable. If you use such a path variable, you need to tell the ideaModule task the name of this variable, so that it can do a proper merge without creating duplicates.
The Antlr plugin extends the Java plugin to add support for generating parsers using Antlr.
To use the Antlr plugin, include in your build script:
The Antlr plugin adds a number of tasks to your project, as shown below.
Table 30.1. Antlr plugin - tasks
Task name | Depends on | Type | Description |
generateGrammarSource
|
- | AntlrTask |
Generates the source files for all production Antlr grammars. |
generateTestGrammarSource
|
- | AntlrTask |
Generates the source files for all test Antlr grammars. |
generate
|
- | AntlrTask |
Generates the source files for all Antlr grammars for the given source set. |
The Antlr plugin adds the following dependencies to tasks added by the Java plugin.
Table 30.2. Antlr plugin - additional task dependencies
Task name | Depends on |
compileJava | generateGrammarSource |
compileTestJava | generateTestGrammarSource |
compileSourceSet Java |
generateSourceSet GrammarSource |
Table 30.3. Antlr plugin - project layout
Directory | Meaning |
src/main/antlr
|
Production Antlr grammar files. |
src/test/antlr
|
Test Antlr grammar files. |
src/
|
Antlr grammar files for the given source set. |
The Antlr plugin adds an antlr
dependency configuration. You use this to declare the
version of Antlr you wish to use.
Example 30.2. Declare Antlr version
build.gradle
repositories {
mavenCentral()
}
dependencies {
antlr 'antlr:antlr:2.7.7'
}
The Antlr plugin adds the following properties to each source set in the project.
Table 30.4. Antlr plugin - source set properties
Property name | Type | Default value | Description |
antlr
|
SourceDirectorySet (read-only)
|
Not null |
The Antlr grammar files of this source set. Contains all .g found in the Antlr
source directories, and excludes all other types of files.
|
antlr.srcDirs
|
Set<File> . Can set using anything described in Section 15.5, “Specifying a set of input files”.
|
[
|
The source directories containing the Antlr grammar files of this source set. |
The Project report plugin is currently a work in progress, and at this stage doesn't do particularly much. We plan to add much more to these reports in future releases of Gradle.
The Project report plugin adds some tasks to your project which generate reports containing useful
information about your build. Those tasks generate exactly the same content as the command line reports triggered
by gradle tasks
, gradle dependencies
and
gradle properties
(seeSection 10.5, “Obtaining information about your build”).
In contrast to the command line reports, the report plugin generates the reports into a file. There is also an
aggregating task that depends on all report tasks added by the plugin.
To use the Project report plugin, include in your build script:
apply plugin: 'project-report'
The project report plugin defines the following tasks:
Table 31.1. Project report plugin - tasks
Task name | Depends on | Type | Description |
dependencyReport
|
- | DependencyReportTask |
Generates the project dependency report. |
propertyReport
|
- | PropertyReportTask |
Generates the project property report. |
taskReport
|
- | TaskReportTask |
Generates the project task report. |
projectReport
|
dependencyReport , propertyReport , taskReport
|
Task |
Generates all project reports. |
The project report defines the following convention properties:
Table 31.2. Project report plugin - convention properties
Property name | Type | Default value | Description |
reportsDirName
|
String
|
reports
|
The name of the directory to generate reports into, relative to the build directory. |
reportsDir
|
File (read-only)
|
|
The directory to generate reports into. |
projects
|
Set<Project>
|
A one element set with the project the plugin was applied to.
|
The projects to generate the reports for. |
projectReportDirName
|
String
|
project
|
The name of the directory to generate the project report into, relative to the reports directory. |
projectReportDir
|
File (read-only)
|
|
The directory to generate the project report into. |
These convention properties are provided by a convention object of type ProjectReportsPluginConvention
.
The Gradle announce plugin enables you to publish messages on succeeded tasks to your favourite platforms. It supports
To use the announce plugin, include in your build script:
After that, configure you username and password (if required for the service you want to announce to) with:
Example 32.2. Configure the announce plugin
build.gradle
announce { username = 'myId' password = 'myPassword' }
Finally, you can use announce with any task by attaching it via task.dolast() as shown below
Example 32.3. Using the announce plugin
build.gradle
task helloWorld << { ant.echo(message: "hello") } helloWorld.doLast { announce("Build complete", "notify-send") announce("Build complete", "twitter") }
As you can see, the syntax in .doLast
is
announce("MESSAGE", "TARGET")
Where MESSAGE is any GString you pass (and might have constructed before). And TARGET might one of the following:
Table 32.1. announce plugin targets
target literal | target | configuration parameters | more information |
username , password | |||
snarl | Snarl Windows Notification Service | ||
growl | Growl Mac OS X Notification Service | ||
notify-send | Notify Ubuntu Notification Service | You need to have notify-send installed for this. Run sudo apt-get install libnotify-bin
on Ubuntu to install it. |
The Gradle application plugin extends the language plugins with common application related tasks. It allows running and bundling applications for the jvm.
To use the application plugin, include in your build script:
To define the main-class for the application you have to set the mainClassName
property as shown below
Example 33.2. Configure the application main class
build.gradle
mainClassName = "org.gradle.sample.Main"
Then, you can run the application by running gradle run
. Gradle will take care of building the application classes,
along with their runtime dependencies, and starting the application with the correct classpath.
The plugin can also build a distribution for your application. The distribution will package up the runtime dependencies of the application
along with some OS specific start scripts. You can run gradle install
to create an image of the application in
build/install/
. You can run projectName
gradle distZip
to create a
ZIP containing the distribution.
The Application plugin adds the following tasks to the project.
Table 33.1. Application plugin - tasks
Task name | Depends on | Type | Description |
run
|
classes
|
JavaExec |
Starts the application. |
startScripts
|
jar
|
CreateStartScripts |
Creates OS specific scripts to run the project as a JVM application. |
install
|
jar , startScripts
|
Sync |
Installs the application into a specified directory. |
distZip
|
jar , startScripts
|
Zip |
Creates a full distribution ZIP archive including runtime libraries and OS specific scripts. |
The application plugin adds some properties to the project, which you can use to configure its behaviour. See Project
.
This chapter gives an overview of issues related with dependency management and presents how Gradle can be used to overcome them.
Gradle offers a very good support for dependency management. If you are familiar with Maven or Ivy approach you will be delighted to learn that:
All the concepts that you already know and like are still there and are fully supported by Gradle. The current dependency management solutions all require to work with XML descriptor files and are usually based on remote repositories for downloading the dependencies. Gradle fully supports this approach.
Gradle works perfectly with your existent dependency management infrastructure, be it Maven or Ivy. All the repositories you have set up with your custom POM or ivy files can be used as they are. No changes necessary.
Additionally, Gradle offers a simpler approach, which might be better suited for some projects.
We think dependency management is very important for almost any project. Yet the kind of dependency management you need depends on the complexity and the environment of your project. Is your project a distribution or a library? Is it part of an enterprise environment, where it is integrated into other projects builds or not? But all types of projects share the following requirements:
The version of the jar must be easy to recognize. Sometimes the version is in the Manifest file of the jar, often not. And even if, it is rather painful to always look into the Manifest file to learn about the version. Therefore we think that you should only use jars which have their version as part of their file name.
It hopes to be clear what are the first level dependencies and what are the transitive ones. There are different ways to achieve this. We will look at this later.
Conflicting versions of the same jar should be detected and either resolved or cause an exception.
Why do we think this is necessary? Without a dependency management as described above, your are likely to burn your fingers sooner or later. If it is unclear which version of a jar your are using, this can introduce subtle bugs which are very hard to find. For example there might be a project which uses Hibernate 3.0.4. There are some problems with Hibernate so a developer installs version 3.0.5 of Hibernate on her machine. This did not solve the problem but she forgot to roll back Hibernate to 3.0.4. Weeks later there is an exception on the integration machine which can't be reproduced on the developer machine. Without a version in the jar name this problem might take a long time to debug. Version in the jar names increases the expressiveness of your project and makes it easier to maintain.
Why is transitive dependency management so important? If you don't know which dependencies are first level dependencies and which ones are transitive you will soon lose control over your build. Even Gradle has already 20+ jars. An enterprise project using Spring, Hibernate, etc. easily ends up with 100+ jars. There is no way to memorize where all these jars come from. If you want to get rid of a first level dependency you can't be sure which other jars you should remove. Because a dependency of a first level dependency might also be a first level dependency itself. Or it might be a transitive dependency of another of your first level dependencies. Many first level dependencies are runtime dependencies and the transitive dependencies are of course all runtime dependencies. So the compiler won't help you much here. The end of the story is, as we have seen very often, no one dares to remove any jar any longer. The project classpath is a complete mess and if a classpath problem arises, hell on earth invites you for a ride. In one of my former projects, I found some ldap related jar in the classpath, whose sheer presence, as I found out after much research, accelerated LDAP access. So removing this jar would not have led to any errors at compile or runtime.
Gradle offers you different ways to express what are first level and what are transitive dependencies. Gradle allows you for example to store your jars in CVS or SVN without XML descriptor files and still use transitive dependency management. Gradle also validates your dependency hierarchy against the reality of your code by using only the first level dependencies for compiling.
In your dependency description you tell Gradle which version of a dependency is needed by another dependency. This frequently leads to conflicts. Different dependencies rely on different versions of another dependency. The JVM unfortunately does not offer yet any easy way, to have different versions of the same jar in the classpath (see Section 34.2.4, “Dependency management and Java”). What Gradle offers you is a resolution strategy, by default the newest version is used. To deal with problems due to version conflicts, reports with dependency graphs are also very helpful. Such reports are another feature of dependency management.
Traditionally, Java has offered no support at all for dealing with libraries and versions. There are
no standard ways to say that
foo-1.0.jar
depends on a bar-2.0.jar
. This has led to proprietary solutions. The most popular ones
are Maven and Ivy. Maven is a complete build system whereas Ivy focuses solely on dependency management.
Both approaches rely on descriptor XML files, which contains information about the dependencies of a particular jar. Both also use repositories where the actual jars are placed together with their descriptor files. And both offer resolution for conflicting jar versions in one form or the other. Yet we think the differences of both approaches are significant in terms of flexibility and maintainability. Beside this, Ivy fully supports the Maven dependency handling. So with Ivy you have access to both worlds. We like Ivy very much. Gradle uses it under the hood for its dependency management. Ivy is most often used via Ant and XML descriptors. But it also has an API. We integrate deeply with Ivy via its API. This enables us to build new concepts on top of Ivy which Ivy does not offer itself.
Right now there is a lot of movement in the field of dependency handling. There is OSGi and there is JSR-294. [10] OSGi is available already, JSR-294 is supposed to be shipped with Java 7. These technologies deal, amongst many other things, also with a painful problem which is neither solved by Maven nor by Ivy. This is enabling different versions of the same jar to be used at runtime.
People who know Ivy have come across most of the concepts we are going to introduce now. But Gradle does not
use any XML for declaring the dependencies (e.g. no ivy.xml
file). It has its own
notation which is part of the Gradle build file.
Dependencies are grouped in configurations. Configurations have a name, a number of other properties,
and they can extend each other. For examples see: Section 9.1, “Artifact configurations”.
If you use the Java plugin, Gradle adds a number of pre-defined configurations to your build. The
plugin also assigns configurations to tasks. See Section 20.5, “Dependency management”
for details. Of course you can add your add custom configurations on top of that. There are many use cases
for custom configurations. This is very handy for example for adding dependencies not needed for
building or testing your software (e.g. additional JDBC drivers to be shipped with your distribution).
The configurations are managed by a configurations
object. The closure you pass to
the configurations object is applied against its API. To learn more about this API have a look at
ConfigurationContainer
.
Module dependencies are the most common dependencies. They correspond to a dependency in an external repository.
Example 34.1. Module dependencies
build.gradle
dependencies { runtime group: 'org.springframework', name: 'spring-core', version: '2.5' runtime 'org.springframework:spring-core:2.5', 'org.springframework:spring-aop:2.5' runtime( [group: 'org.springframework', name: 'spring-core', version: '2.5'], [group: 'org.springframework', name: 'spring-aop', version: '2.5'] ) runtime('org.hibernate:hibernate:3.0.5') { transitive = true } runtime group: 'org.hibernate', name: 'hibernate', version: '3.0.5', transitive: true runtime(group: 'org.hibernate', name: 'hibernate', version: '3.0.5') { transitive = true } }
Gradle provides different notations for module dependencies. There is a string notation and
a map notation. A module dependency has an API which allows for further configuration. Have a look at
ExternalModuleDependency
to learn all about the API.
This API provides properties and configuration methods. Via the string notation you can define a subset
the properties. With the map notation you can define all properties. To have access to the complete API,
either with the map or with the string notation, you can assign a single dependency to a configuration
together with a closure.
If you declare a module dependency, Gradle looks for a corresponding module descriptor file (pom.xml
or
ivy.xml
) in the repositories. If such a module descriptor file exists, it is parsed and the artifacts of
this module (e.g. hibernate-3.0.5.jar
) as well as its dependencies (e.g. cglib) are downloaded. If no such
module descriptor file exists, Gradle looks for a file called hibernate-3.0.5.jar
to retrieve. In Maven
a module can only have one and only one artifact. In Gradle and Ivy a module can have multiple artifacts.
Each artifact can have a different set of dependencies.
As said above, if no module descriptor file can be found, Gradle by default
downloads a jar with the name of the module. But sometimes, even if the repository contains module descriptors, you want to download only the artifact jar, without
the dependencies.
[11]
And sometimes you want to download a zip from a repository, that does not have module descriptors.
Gradle provides an artifact only notation for those use cases - simply prefix the extension that you want to be downloaded with '@'
sign:
Example 34.2. Artifact only notation
build.gradle
dependencies { runtime "org.groovy:groovy:1.5.6@jar" runtime group: 'org.groovy', name: 'groovy', version: '1.5.6', ext: 'jar' }
An artifact only notation creates a module dependency which downloads only the artifact file with
the specified extension. Existing module descriptors are ignored.
The Maven dependency management has the notion of classifiers. [12] Gradle supports this. To retrieve classified dependencies from a maven repository you can write:
Example 34.3. Dependency with classifier
build.gradle
compile "org.gradle.test.classifiers:service:1.0:jdk15@jar" otherConf group: 'org.gradle.test.classifiers', name: 'service', version: '1.0', classifier: 'jdk14'
As you can see in the example, classifiers can be used together with setting an explicit extension (artifact only notation).
Client module dependencies enable you to declare transitive dependencies directly in your build script. They are a replacement for a module descriptor XML file in an external repository.
Example 34.4. Client module dependencies - transitive dependencies
build.gradle
dependencies { runtime module("org.codehaus.groovy:groovy-all:1.7.10") { dependency("commons-cli:commons-cli:1.0") { transitive = false } module(group: 'org.apache.ant', name: 'ant', version: '1.8.2') { dependencies "org.apache.ant:ant-launcher:1.8.2@jar", "org.apache.ant:ant-junit:1.8.2" } } }
This declares a dependency of your project on Groovy. Groovy itself has dependencies. But Gradle does
not look for an XML descriptor to figure them out but gets the information from the build file. The
dependencies of a client module can be normal module dependencies or artifact dependencies or another
client module. Have also a look at the API documentation: ClientModule
In the current release client modules have one limitation. Let's say your project is a library and you want this library to be uploaded to your company's Maven or Ivy repository. Gradle uploads the jars of your project to the company repository together with the XML descriptor file of the dependencies. If you use client modules the dependency declaration in the XML descriptor file is not correct. We will improve this in a future release of Gradle.
Gradle distinguishes between external dependencies and dependencies on projects which are part of the same multi-project build. For the latter you can declare Project Dependencies.
For more information see the API documentation for ProjectDependency
Multi-project builds are discussed in Chapter 38, Multi-project Builds.
File dependencies allow you to directly add a set of files to a configuration, without first adding them to a repository. This can be useful if you cannot, or do not want to, place certain files in a repository. Or if you do not want to use any repositories at all for storing your dependencies.
To add some files as a dependency for a configuration, you simply pass a file collection as a dependency:
Example 34.6. File dependencies
build.gradle
dependencies { runtime files('libs/a.jar', 'libs/b.jar') runtime fileTree(dir: 'libs', include: '*.jar') }
File dependencies are not included in the published dependency descriptor for your project. However, file dependencies are included in transitive project dependencies within the same build. This means they cannot be used outside the current build, but they can be used with the same build.
You can declare which tasks produce the files for a file dependency. You might do this when, for example, the files are generated by the build.
Example 34.7. Generated file dependencies
build.gradle
dependencies { compile files("$buildDir/classes") { builtBy 'compile' } } task compile << { println 'compiling classes' } task list(dependsOn: configurations.compile) << { println "classpath = ${configurations.compile.collect {File file -> file.name}}" }
Output of gradle -q list
> gradle -q list compiling classes classpath = [classes]
You can declare a dependency on the API of the current version of Gradle by using the
DependencyHandler.gradleApi()
method. This is
useful when you are developing custom Gradle tasks or plugins.
You can exclude a transitive dependency either by configuration or by dependency:
Example 34.9. Excluding transitive dependencies
build.gradle
configurations { compile.exclude module: 'commons' all*.exclude group: 'org.gradle.test.excludes', module: 'reports' } dependencies { compile("org.gradle.test.excludes:api:1.0") { exclude module: 'shared' } }
If you define
an exclude for a particular configuration, the excluded transitive dependency will be filtered for all
dependencies when resolving this configuration or any inheriting configuration.
If you want to exclude a transitive dependency from all your
configurations you can use the Groovy spread-dot operator to express this in a concise way, as shown in the example.
When defining an exclude, you can
specify either only the organization or only the module name or both.
Have also a look at the API documentation of Dependency
and
Configuration
.
All attributes for a dependency are optional, except the name. It depends on the repository type, which information is need for actually finding the dependencies in the repository. See Section 34.5, “Repositories”. If you work for example with Maven repositories, you need to define the group, name and version. If you work with filesystem repositories you might only need the name or the name and the version.
Example 34.10. Optional attributes of dependencies
build.gradle
dependencies { runtime ":junit:4.8.2", ":testng" runtime name: 'testng' }
You can also assign collections or arrays of dependency notations to a configuration:
Example 34.11. Collections and arrays of dependencies
build.gradle
List groovy = ["org.codehaus.groovy:groovy-all:1.7.10@jar", "commons-cli:commons-cli:1.0@jar", "org.apache.ant:ant:1.8.2@jar"] List hibernate = ['org.hibernate:hibernate:3.0.5@jar', 'somegroup:someorg:1.0@jar'] dependencies { runtime groovy, hibernate }
In Gradle a dependency can have different configurations (as your project can have different configurations). If you don't specify anything explicitly, Gradle uses the default configuration of the dependency. For dependencies from a Maven repository, the default configuration is the only available one anyway. If you work with Ivy repositories and want to declare a non-default configuration for your dependency you have to use the map notation and declare:
Example 34.12. Dependency configurations
build.gradle
dependencies { runtime group: 'org.somegroup', name: 'somedependency', version: '1.0', configuration: 'someConfiguration' }
To do the same for project dependencies you need to declare:
Example 34.13. Dependency configurations for project
build.gradle
dependencies { compile project(path: ':api', configuration: 'spi') }
You can generate dependency reports from the command line (see Section 10.5.3, “Listing project dependencies”). With the help of the Project report plugin (see Chapter 31, The Project Report Plugin) such a report can be created by your build.
For the examples below we have the following dependencies setup:
Example 34.14. Configuration.copy
build.gradle
configurations { sealife alllife.extendsFrom sealife } dependencies { sealife "sea.mammals:orca:1.0", "sea.fish:shark:1.0", "sea.fish:tuna:1.0" alllife "air.birds:albatros:1.0" }
The dependencies have the following transitive dependencies:
shark-1.0 -> seal-2.0, tuna-1.0
orca-1.0 -> seal-1.0
tuna-1.0 -> herring-1.0
You can use the configuration to access the declared dependencies or a subset of those:
Example 34.15. Accessing declared dependencies
build.gradle
task dependencies << {
configurations.alllife.dependencies.each { dep -> println dep.name }
println()
configurations.alllife.allDependencies.each { dep -> println dep.name }
println()
configurations.alllife.allDependencies.findAll { dep -> dep.name != 'orca' }.each { dep -> println dep.name }
}
Output of gradle -q dependencies
> gradle -q dependencies albatros albatros orca shark tuna albatros shark tuna
dependencies
returns only the dependencies belonging explicitly to the configuration.
allDependencies
includes the dependencies from extended
configurations.
To get the library files of the configuration dependencies you can do:
Example 34.16. Configuration.files
build.gradle
task allFiles << { configurations.sealife.files.each { file -> println file.name } }
Output of gradle -q allFiles
> gradle -q allFiles orca-1.0.jar seal-2.0.jar shark-1.0.jar tuna-1.0.jar herring-1.0.jar
Sometimes you want the library files of a subset of the configuration dependencies (e.g. of a single dependency).
Example 34.17. Configuration.files with spec
build.gradle
task files << {
configurations.sealife.files { dep -> dep.name == 'orca' }.each { file ->
println file.name
}
}
Output of gradle -q files
> gradle -q files orca-1.0.jar seal-2.0.jar
The Configuration.files
method always retrieves all artifacts of the whole configuration. It
then filters the retrieved files by specified dependencies. As you can see in the example, transitive dependencies are included.
You can also copy a configuration. You can optionally specify that only a subset of dependencies from the orginal configuration
should be copied. The copying methods come in two flavors. The copy
method copies only the dependencies belonging
explicitly to the configuration. The copyRecursive
method copies all the dependencies, including the dependencies from extended
configurations.
Example 34.18. Configuration.copy
build.gradle
task copy << {
configurations.alllife.copyRecursive { dep -> dep.name != 'orca' }.allDependencies.each { dep ->
println dep.name
}
println()
configurations.alllife.copy().allDependencies.each { dep ->
println dep.name
}
}
Output of gradle -q copy
> gradle -q copy albatros shark tuna albatros
It is important to note that the returned files of the copied configuration are often but not always the same than the returned files of the dependency subset of the original configuration. In case of version conflicts between dependencies of the subset and dependencies not belonging to the subset the resolve result might be different.
Example 34.19. Configuration.copy vs. Configuration.files
build.gradle
task copyVsFiles << { configurations.sealife.copyRecursive { dep -> dep.name == 'orca' }.each { file -> println file.name } println() configurations.sealife.files { dep -> dep.name == 'orca' }.each { file -> println file.name } }
Output of gradle -q copyVsFiles
> gradle -q copyVsFiles orca-1.0.jar seal-1.0.jar orca-1.0.jar seal-2.0.jar
In the example above, orca
has a dependency on seal-1.0
whereas
shark
has a dependency on seal-2.0
. The original configuration has therefore a version
conflict which is resolved to the newer seal-2.0
version. The files
method therefore
returns seal-2.0
as a transitive dependency of orca
. The copied configuration only has orca
as a dependency and therefore there is no version conflict and seal-1.0
is returned as a transitive
dependency.
Once a configuration is resolved it is immutable. Changing its state or the state of one of its dependencies will cause an exception. You can always copy a resolved configuration. The copied configuration is in the unresolved state and can be freshly resolved.
To learn more about the API of the configuration class see the API documentation:
Configuration
.
Gradle repository management, based on Apache Ivy, gives you a lot of freedom regarding repository layout and retrieval policies. Additionally Gradle provides various convenience method to add preconfigured repositories.
To add the central Maven2 repository (http://repo1.maven.org/maven2) simply type:
Now Gradle will look for your dependencies in this repository.
Quite often certain jars are not in the official Maven repository for licensing reasons (e.g. JTA), but its POMs are.
Example 34.21. Adding several Maven repositories
build.gradle
repositories { mavenCentral name: 'single-jar-repo', urls: "http://repo.mycompany.com/jars" mavenCentral name: 'multi-jar-repos', urls: ["http://repo.mycompany.com/jars1", "http://repo.mycompany.com/jars2"] }
Gradle will look first in the central Maven repository for the POM and the JAR. If the JAR can't be found there, it will look for it in the other repositories.
For adding a custom Maven repository you can say:
Example 34.22. Adding custom Maven repository
build.gradle
repositories {
mavenRepo urls: "http://repo.mycompany.com/maven2"
}
To declare additional repositories to look for jars (like above in the example for the central Maven repository), you can say:
Example 34.23. Adding additional Maven repositories for JAR files
build.gradle
repositories { mavenRepo urls: ["http://repo2.mycompany.com/maven2", "http://repo.mycompany.com/jars"] }
The first URL is used to look for POMs and JARs. The subsequent URLs are used to look for JARs.
To use the local Maven cache as a repository you can say:
Example 34.24. Adding the local Maven cache as a repository
build.gradle
repositories { mavenLocal() }
To access a password protected Maven repository (basic authentication) you need to use one of Ivy features:
Example 34.25. Accessing password protected Maven repository
build.gradle
org.apache.ivy.util.url.CredentialsStore.INSTANCE.addCredentials("REALM", "HOST", "USER", "PASSWORD");
Host name should not include "http://"
prefix. It is advisable to keep your login and password in gradle.properties
rather than directly in the build file.
If you want to use a (flat) filesytem directory as a repository, simply type:
Example 34.26. Flat repository resolver
build.gradle
repositories { flatDir name: 'localRepository', dirs: 'lib' flatDir dirs: ['lib1', 'lib2'] }
This adds repositories which look into one or more directories for finding dependencies. If you only work with flat directory resolvers you don't need to set all attributes of a dependency. See Section 34.3.8, “Optional attributes”
The methods above for creating preconfigured repositories share some common behavior. For all of them, defining a name for the repository is optional. If no name is defined a default name is calculated, depending on the type of the repository. You might want to assign a name, if you want to access the declared repository. For example if you want to use it also for uploading your project artifacts. An explicit name might also be helpful when studying the debug output.
The values passed as arguments to the repository methods can be of any type, not just String. The value
that is actually used, is the toString
result of the argument object.
When Gradle downloads dependencies from remote repositories it stores them in a local cache located at
USER_HOME/.gradle/cache
. When Gradle downloads dependencies from one of its
predefined local resolvers (e.g. Flat Directory resolver), the cache is not used as an intermediate
storage for dependency artifacts. The cache is always used for caching module descriptors.
Gradle, thanks to Ivy under its hood, is extremely flexible regarding repositories:
There are many options for the protocol to communicate with the repository (e.g. filesystem, http, ssh, ...)
Each repository can have its own layout.
Let's say, you declare a dependency on the
junit:junit:3.8.2
library.
Now how does Gradle find it in the repositories? Somehow the dependency information has to be mapped to a
path. In contrast to Maven, where this path is fixed, with Gradle you can define a pattern that defines
what the path will look like. Here are some examples:
[13]
// Maven2 layout (if a repository is marked as Maven2 compatible, the organization (group) is split into subfolders according to the dots.) someroot/[organisation]/[module]/[revision]/[module]-[revision].[ext] // Typical layout for an ivy repository (the organization is not split into subfolder) someroot/[organisation]/[module]/[revision]/[type]s/[artifact].[ext] // Simple layout (the organization is not used, no nested folders.) someroot/[artifact]-[revision].[ext]
To add any kind of repository (you can pretty easy write your own ones) you can do:
Example 34.27. Definition of a custom repository
build.gradle
repositories { add(new org.apache.ivy.plugins.resolver.FileSystemResolver()) { name = 'repo' addIvyPattern "$projectDir/repo/[organisation]/[module]-ivy-[revision].xml" addArtifactPattern "$projectDir/repo/[organisation]/[module]-[revision](-[classifier]).[ext]" descriptor = 'optional' checkmodified = true } }
An overview of which Resolvers are offered by Ivy and thus also by Gradle can be found here. With Gradle you just don't configure them via XML but directly via their API.
Many projects rely on the Maven2 repository. This is not without problems.
The IBibilio repository can be down or has a very long response time.
The pom.xml
's of many projects have wrong information (as one example, the POM of
commons-httpclient-3.0
declares JUnit as a runtime dependency).
For many projects there is not one right set of dependencies (as more or less imposed by the
pom
format).
If your project relies on the IBibilio repository you are likely to need an additional custom repository, because:
You might need dependencies that are not uploaded to IBibilio yet.
You want to deal properly with wrong metadata in a IBibilio pom.xml
.
You don't want to expose people who want to build your project, to the downtimes or sometimes very long response times of IBibilio.
It is not a big deal to set-up a custom repository. [14] But it can be tedious, to keep it up to date. For a new version, you have always to create the new XML descriptor and the directories. And your custom repository is another infrastructure element which might have downtimes and needs to be updated. To enable historical builds, you need to keep all the past libraries and you need a backup. It is another layer of indirection. Another source of information you have to lookup. All this is not really a big deal but in its sum it has an impact. Repository Manager like Artifactory or Nexus make this easier. But for example open source projects don't usually have a host for those products.
This is a reason why some projects prefer to store their libraries in their version control system. This approach is fully supported by Gradle. The libraries can be stored in a flat directory without any XML module descriptor files. Yet Gradle offers complete transitive dependency management. You can use either client module dependencies to express the dependency relations, or artifact dependencies in case a first level dependency has no transitive dependencies. People can check out such a project from svn and have everything necessary to build it.
If you are working with a distributed version control system like Git you probably don't want to use the version control system to store libraries as people check out the whole history. But even here the flexibility of Gradle can make your life easier. For example you can use a shared flat directory without XML descriptors and yet you can have full transitive dependency management as described above.
You could also have a mixed strategy. If your main concern is bad metadata in the pom.xml
and maintaining
custom XML descriptors,
Client Modules
offer an alternative. But you can of course still use Maven2 repo and your custom repository as a
repository for
jars only
and still enjoy
transitive
dependency management. Or you can only provide client modules for POMs with bad metadata. For the
jars and the correct POMs you still use the remote repository.
There is another way to deal with transitive dependencies without XML descriptor files. You can do this with Gradle, but we don't recommend it. We mention it for the sake of completeness and comparison with other build tools.
The trick is to use only artifact dependencies and group them in lists. That way you have somehow
expressed, what are your first level dependencies and what are transitive dependencies (see
Section 34.3.8, “Optional attributes”).
But the draw-back is, that for the Gradle dependency management all dependencies are considered first level dependencies. The
dependency reports don't show your real dependency graph and the
compile
task uses all dependencies, not just the first level dependencies. All in all, your build is less
maintainable and reliable than it could be when using client modules. And you don't gain anything.
[10] JSR 294: Improved Modularity Support in the JavaTM Programming Language, http://jcp.org/en/jsr/detail?id=294
[11] Gradle supports partial multiproject builds (seeChapter 38, Multi-project Builds).
[12] http://www.sonatype.com/books/maven-book/reference/pom-relationships-sect-project-relationships.html
[13] At http://ant.apache.org/ivy/history/latest-milestone/concept.html you can learn more about ivy patterns.
[14] If you want to shield your project from the downtimes of IBibilio things get more complicated. You probably want to set-up a repository proxy for this. In an enterprise environment this is rather common. For an open source project it looks like overkill.
This chapter is about how you declare what are the artifacts of your project and how to work with them (e.g. upload them). We define the artifacts of the projects as the files the project want to provide to the outside world. This can be a library or a distribution or any other file. Usually artifacts are archives, but not necessarily. In the Maven world a project can provide only one artifact. With Gradle a project can provide as many artifacts as needed.
Like dependencies, artifacts are grouped by configurations. In fact, a configuration can contain both, artifacts and dependencies, at the same time. To assign an artifact to a configuration, you can write:
Example 35.1. Assignment of an artifact to a configuration
build.gradle
task myJar(type: Jar) artifacts { archives myJar }
What do you gain by assigning an artifact to a configuration? For each configuration (also for the custom
ones added by you) Gradle provides the tasks upload[ConfigurationName]
and
build[ConfigurationName]
.
[15]
Execution of these tasks will build or upload the artifacts belonging to
the respective configuration.
Table Table 20.5, “Java plugin - dependency configurations” shows the configurations added by the Java plugin. Two of the
configurations are relevant for the usage with artifacts. The archives
configuration is the standard
configuration to assign your artifacts to. The Java plugin automatically assigns the default jar to this
configuration. We will talk more about the default
configuration in Section 35.4, “More about project libraries”.
As with dependencies, you can declare as many custom configurations as you like and assign artifacts to them.
It is important to note that the custom archives you are creating as part of your build are not automatically assigned to any configuration. You have to explicitly do this assignment.
We have said that there is a specific upload task for each configuration. But before you can do an upload, you have to configure the upload task and define where to upload. The repositories you have defined (as described in Section 34.5, “Repositories”) are not automatically used for uploading. In fact, some of those repositories allow only for artifacts downloading. Here is an example how you can configure the upload task of a configuration:
Example 35.2. Configuration of the upload task
build.gradle
repositories { flatDir(name: 'fileRepo', dirs: "$projectDir/repo") } uploadArchives { uploadDescriptor = false repositories { add project.repositories.fileRepo add(new org.apache.ivy.plugins.resolver.SshResolver()) { name = 'sshRepo' user = 'username' userPassword = 'pw' host = "http://repo.mycompany.com" } } }
As you can see, you can either use a reference to an existing repository or create a new repository. As described in Section 34.5.5, “More about Ivy resolvers”, you can use all the Ivy resolvers suitable for the purpose of uploading.
Uploading to a Maven repository is described in Section 36.6, “Interacting with Maven repositories”.
If your project is supposed to be used as a library, you need to define what are the artifacts of this library
and what are the dependencies of these artifacts. The Java plugin adds a default
configuration for
this purpose. This configuration extends both the archives
and the runtime
configuration,
with the implicit assumption that the runtime
dependencies are the dependencies of the archives
configuration. Of course this is fully customizable. You can add your own custom configuration or let the the
existing configurations extends from other configurations. You might have different group of artifacts which have
a different set of dependencies. This mechanism is very powerful and flexible.
If someone wants to use your project as a library, she simply needs to declare on which configuration of
the dependency to depend on.
A Gradle dependency offers the configuration
property to declare this. If this
is not specified, the default
configuration is used (see Section 34.3.9, “Dependency configurations”).
Using your project as a library
can either happen from within a multi-project build or by retrieving your project from a repository. In
the latter case, an ivy.xml descriptor in the repository is supposed to contain all the neccesary information. If you
work with Maven repositories you don't have the flexibility as described above. For how to publish to a Maven
repository, see the section Section 36.6, “Interacting with Maven repositories”.
[15] To be exact, the Base plugin provides those tasks. The BasePlugin is automatically applied, if you use the Java plugin.
This chapter is a work in progress
The Maven plugin adds support for deploying artifacts to Maven repositories.
To use the Maven plugin, include in your build script:
The Maven plugin defines the following tasks:
Table 36.1. Maven plugin - tasks
Task name | Depends on | Type | Description |
install
|
All tasks that build the associated archives. | Upload |
Installs the associated artifacts to the local Maven cache, including Maven metadata generation.
By default the install task is associated with the archives configuration. This
configuration has by default only the default jar as an element. To learn more about installing to the
local repository, see: Section 36.6.3, “Installing to the local repository” |
The Maven plugin defines the following convention properties:
Table 36.2. Maven plugin - properties
Property name | Type | Default value | Description |
pomDirName
|
String
|
poms
|
The path of the directory to write the generated POMs, relative to the build directory. |
pomDir
|
File (read-only)
|
|
The directory where the generated POMs are written to. |
conf2ScopeMappings
|
|
n/a
|
Instructions for mapping Gradle configurations to Maven scopes. See Section 36.6.4.2, “Dependency mapping”. |
These properties are provided by a MavenPluginConvention
convention object.
The maven plugin provides a factory method for creating a POM. This is useful if you need a POM without the context of uploading to a Maven repo.
Example 36.2. Creating a stand alone pom.
build.gradle
task writeNewPom << { pom { project { inceptionYear '2008' licenses { license { name 'The Apache Software License, Version 2.0' url 'http://www.apache.org/licenses/LICENSE-2.0.txt' distribution 'repo' } } } }.writeTo("$buildDir/newpom.xml") }
Amongst other things, Gradle supports the same builder syntax as polyglot Maven. To learn more about the Gradle Maven POM object, see
MavenPom
. See also: MavenPluginConvention
With Gradle you can deploy to remote Maven repositories or install to your local Maven repository. This includes all Maven metadata manipulation and works also for Maven snapshots. In fact, Gradle's deployment is 100 percent Maven compatible as we use the native Maven Ant tasks under the hood.
Deploying to a Maven repository is only half the fun if you don't have a POM. Fortunately Gradle can generate this POM for you using the dependency information it has.
Let's assume your project produces just the default jar file. Now you want to deploy this jar file to a remote Maven repository.
Example 36.3. Upload of file to remote Maven repository
build.gradle
apply plugin: 'maven' uploadArchives { repositories.mavenDeployer { repository(url: "file://localhost/tmp/myRepo/") } }
That is all. Calling the
uploadArchives
task will generate the POM and deploys the artifact and the pom to the specified repository.
There is some more work to do if you need support for other protocols than file
. In
this case the native Maven code we delegate to needs additional libraries. Which libraries depend on the
protocol you need. The available protocols and the corresponding libraries are listed in Table 36.3, “Protocol jars for Maven deployment” (those libraries have again transitive dependencies which have transitive
dependencies).
[16]
For example to use the ssh protocol you can do:
Example 36.4. Upload of file via SSH
build.gradle
configurations { deployerJars } repositories { mavenCentral() } dependencies { deployerJars "org.apache.maven.wagon:wagon-ssh:1.0-beta-2" } uploadArchives { repositories.mavenDeployer { name = 'sshDeployer' // optional configuration = configurations.deployerJars repository(url: "scp://repos.mycompany.com/releases") { authentication(userName: "me", password: "myPassword") } } }
There are many configuration options for the Maven deployer. The configuration is done via a Groovy builder. All the elements of this tree are Java beans. To configure the simple attributes you pass a map to the bean elements. To add another bean elements to its parent, you use a closure. In the example above repository and authentication are such bean elements. Table 36.4, “Configuration elements of the MavenDeployer” lists the available bean elements and a link to the javadoc of the corresponding class. In the javadoc you can see the possible attributes you can set for a particular element.
In Maven you can define repositories and optionally snapshot repositories. If no snapshot repository
is defined, releases and snapshots are both deployed to the
repository
element. Otherwise snapshots are deployed to the
snapshotRepository
element.
Table 36.3. Protocol jars for Maven deployment
Protocol | Library |
http | org.apache.maven.wagon:wagon-http:1.0-beta-2 |
ssh | org.apache.maven.wagon:wagon-ssh:1.0-beta-2 |
ssh-external | org.apache.maven.wagon:wagon-ssh-external:1.0-beta-2 |
scp | org.apache.maven.wagon:wagon-scp:1.0-beta-2 |
ftp | org.apache.maven.wagon:wagon-ftp:1.0-beta-2 |
webdav | org.apache.maven.wagon:wagon-webdav-jackrabbit:1.0-beta-6 |
file | - |
Table 36.4. Configuration elements of the MavenDeployer
Element | Javadoc |
root |
MavenDeployer
|
repository | org.apache.maven.artifact.ant.RemoteRepository |
authentication | org.apache.maven.artifact.ant.Authentication |
releases | org.apache.maven.artifact.ant.RepositoryPolicy |
snapshots | org.apache.maven.artifact.ant.RepositoryPolicy |
proxy | org.apache.maven.artifact.ant.Proxy |
snapshotRepository | org.apache.maven.artifact.ant.RemoteRepository |
The Maven plugin adds an install
task to your project. This task depends on all the archives
task of the archives
configuration. It installs those archives to your local Maven repository.
If the default location for the local repository is redefined in a Maven settings.xml
, this is
considered by this task.
The Maven POMs for uploading are automatically generated by Gradle. The groupId, artifactId, version and packaging
values are taken from the project object. The dependency elements are created from the Gradle dependency declarations.
You can find the generated POMs in the directory
<buildDir>/poms
. You can further customize the POM via the API of the
MavenPom
object.
You might want the artifact deployed to the maven repository to have a different version or name than the artifact generated by Gradle. To customize these you can do:
Example 36.5. Customization of pom
build.gradle
uploadArchives { repositories.mavenDeployer { repository(url: "file://localhost/tmp/myRepo/") pom.version = '1.0Maven' pom.artifactId = 'myMavenName' } }
Or you want to add new elements like license information.
Example 36.6. Builder style customization of pom
build.gradle
uploadArchives { repositories.mavenDeployer { repository(url: "file://localhost/tmp/myRepo/") pom.project { licenses { license { name 'The Apache Software License, Version 2.0' url 'http://www.apache.org/licenses/LICENSE-2.0.txt' distribution 'repo' } } } } }
We use a builder here. You could also add the artifactId and groupId via the builder.
The pom object offers a whenConfigure
method, if you need to modify the
autogenerated content.
Example 36.7. Modifying auto-generated content
build.gradle
[installer, deployer]*.pom*.whenConfigured {pom -> pom.dependencies.find {dep -> dep.groupId == 'group3' && dep.artifactId == 'runtime' }.optional = true }
If you have more than one artifact to publish, things work a little bit differently. SeeSection 36.6.4.1, “Multiple artifacts per project”.
To customize the settings for the Maven installer (seeSection 36.6.3, “Installing to the local repository”), you can do:
Example 36.8. Customization of Maven installer
build.gradle
configure(install.repositories.mavenInstaller) { pom.project { version '1.0Maven' artifactId 'myName' } }
In contrast to the example above we use the builder here for changing groupId and artifactId.
Maven can only deal with one artifact per project. This is reflected in the structure of the
Maven POM. We think there are many situations where it makes sense to have more than one artifact per
project. In such a case you need to generate multiple POMs. In such a case you have to explicitly declare each artifact
you want to publish to a Maven repository. The MavenDeployer
and the MavenInstaller
both provide an API for this:
Example 36.9. Generation of multiple poms
build.gradle
uploadArchives { repositories.mavenDeployer { repository(url: "file://localhost/tmp/myRepo/") addFilter('api') {artifact, file -> artifact.name == 'api' } addFilter('service') {artifact, file -> artifact.name == 'service' } pom('api').version = 'mySpecialMavenVersion' } }
You need to declare a filter for each artifact you want to publish. This filter defines a boolean expression for
which Gradle artifact it accepts. Each filter has a POM associated with it which you can configure.
To learn more about this have a look at PomFilterContainer
and its associated classes.
The Maven plugin configures the default mapping between the Gradle configurations added by the
Java and War plugin and the Maven scopes. Most
of the time you don't need to touch this and you can safely skip this section. The mapping
works like the following. You can map a configuration to one and only one scope. Different
configurations can be mapped to one or different scopes. One can assign also a priority to a particular
configuration-to-scope mapping. Have a look at
Conf2ScopeMappingContainer
to learn more. To access the mapping configuration you can say:
Example 36.10. Accessing a mapping configuration
build.gradle
task mappings << { println conf2ScopeMappings.mappings }
Gradle exclude rules are converted to Maven excludes if possible. Such a conversion is possible if in the Gradle exclude rule the group as well as the module name is specified (as Maven needs both in contrast to Ivy). Per-configuration excludes are also included in the Maven POM, if they are convertible.
We said earlier, that the core of Gradle is a language for dependency based programming. In Gradle terms this means that you can define tasks and dependencies between tasks. Gradle guarantees that these tasks are executed in the order of their dependencies, and that each task is executed only once. Those tasks form a Directed Acyclic Graph. There are build tools that build up such a dependency graph as they execute their tasks. Gradle builds the complete dependency graph before any task is executed. This lies at the heart of Gradle and makes many things possible which would not be possible otherwise.
Your build scripts configure this dependency graph. Therefore they are strictly speaking build configuration scripts.
A Gradle build has three distinct phases.
Gradle supports single and multi-project builds. During the initialization phase, Gradle
determines which projects are going to take part in the build, and creates a
Project
instance for each of these projects.
The build scripts of all projects which are part of the build are executed. This configures the project objects.
Gradle determines the subset of the tasks, created and configured during the configuration phase, to be executed. The subset is determined by the task name arguments passed to the gradle command and the current directory. Gradle then executes each of the selected tasks.
Beside the build script files, Gradle defines a settings file. The settings file is determined by Gradle
via a naming convention. The default name for this file is settings.gradle
. Later in
this chapter we explain, how Gradle looks for a settings file.
The settings file gets executed during the initialization phase. A multiproject build must have a
settings.gradle
file in the root project of the multiproject hierarchy. It is required because in the
settings file it is defined, which projects are taking part in the multi-project build (see
Chapter 38, Multi-project Builds). For a single-project build, a settings file is optional.
You might need it for example, to add libraries to your build script classpath (see Chapter 41, Organizing Build Logic). Let's first do some introspection with a single project
build:
Example 37.1. Single project build
settings.gradle
println 'This is executed during the initialization phase.'
build.gradle
println 'This is executed during the configuration phase.' task configured { println 'This is also executed during the configuration phase.' } task test << { println 'This is executed during the execution phase.' }
Output of gradle test
> gradle test This is executed during the initialization phase. This is executed during the configuration phase. This is also executed during the configuration phase. :test This is executed during the execution phase. BUILD SUCCESSFUL Total time: 1 secs
For a build script, the property access and method calls are delegated to a project object. Similarly
property access and method calls within the settings file is delegated to a settings object. Have a look at
Settings
.
A multi-project build is a build where you build more than one project during a single execution of Gradle. You have to declare the projects taking part in the multiproject build in the settings file. There is much more to say about multi-project builds in the chapter dedicated to this topic (see Chapter 38, Multi-project Builds).
Multi-project builds are always represented by a tree with a single root. Each element in the tree
represent a project. A project has a virtual and a physical path. The virtual path denotes the position
of the project in the multi-project build tree. The project tree is created in the
settings.gradle
file. By default it is assumed that the location of the settings
file is also the location of the root project. But you can redefine the location of the root project
in the settings file.
In the settings file you can use a set of methods to build the project tree. Hierarchical and flat physical layouts get special support.
The include
method takes as an argument a relative virtual path to the root
project. This relative virtual path is assumed to be equal to the relative physical path of the
subproject to the root project. You only need to specify the leafs of the tree. Each parent path of
the leaf project is assumed to be another subproject which obeys to the physical path assumption
described above.
The includeFlat
method takes directory names as an argument. Those directories
need to exist at the same level as the root project directory. The location of those directories
are considered as child projects of the root project in the virtual multi-project tree.
The multi-project tree created in the settings file is made up of so called project descriptors. You can modify these descriptors in the settings file at any time. To access a descriptor you can do:
Example 37.4. Modification of elements of the project tree
settings.gradle
println rootProject.name
println project(':projectA').name
Using this descriptor you can change the name, project directory and build file of a project.
Example 37.5. Modification of elements of the project tree
settings.gradle
rootProject.name = 'main' project(':projectA').projectDir = new File(settingsDir, '../my-project-a') project(':projectA').buildFileName = 'projectA.gradle'
Have a look at ProjectDescriptor
for more details.
How does Gradle know whether to do a single or multiproject build? If you trigger a multiproject build
from the directory where the settings file is, things are easy. But Gradle also allows you to execute the
build from within any subproject taking part in the build.
[17]
If you execute Gradle from within a project that has no settings.gradle
file,
Gradle does the following:
It searches for a settings.gradle
in a directory called master
which has the same nesting level as the current dir.
If no settings.gradle
is found, it searches the parent directories for the existence of a
settings.gradle
file.
If no settings.gradle
file is found, the build is executed as a single project build.
If a settings.gradle
file is found, Gradle checks if the current project is part of the
multiproject hierarchy defined in the found settings.gradle
file. If not, the build is executed as a
single project build. Otherwise a multiproject build is executed.
What is the purpose of this behavior? Somehow Gradle has to find out, whether the project you are into, is
a subproject of a multiproject build or not. Of course, if it is a subproject, only the subproject and its
dependent projects are build. But Gradle needs to create the build configuration for the whole multiproject
build (see Chapter 38, Multi-project Builds). Via the -u
command line option, you can tell Gradle not to look in the parent hierarchy for a settings.gradle
file. The
current project is then always build as a single project build. If the current project contains a
settings.gradle
file, the -u
option has no meaning. Such a build is always executed as:
a single project build, if the settings.gradle
file does not define a multiproject hierarchy
a multiproject build, if the settings.gradle
file does define a multiproject hierarchy.
The auto search for a settings file does only work for multi-project builds with a physical hierarchical or flat layout. For a flat layout you must additionally obey to the naming convention described above. Gradle supports arbitrary physical layouts for a multiproject build. But for such arbitrary layouts you need to execute the build from the directory where the settings file is located. For how to run partial builds from the root see Section 38.4, “Running tasks by their absolute path”. In our next release we want to enable partial builds from subprojects by specifying the location of the settings file as a command line parameter. Gradle creates Project objects for every project taking part in the build. For a single project build this is only one project. For a multi-project build these are the projects specified in Settings object (plus the root project). Each project object has by default a name equals to the name of its top level directory. Every project except the root project has a parent project and might have child projects.
For a single project build, the workflow of the after initialization phases are pretty simple. The build script is executed against the project object that was created during the initialization phase. Then Gradle looks for tasks with names equal to those passed as command line arguments. If these task names exist, they are executed as a separate build in the order you have passed them. The configuration and execution for multi-project builds is discussed in Chapter 38, Multi-project Builds.
Your build script can receive notifications as the build progresses through its lifecyle. These notifications generally take 2 forms: You can either implement a particular listener interface, or you can provide a closure to execute when the notification is fired. The examples below use closures. For details on how to use the listener interfaces, refer to the API documentation.
You can receive a notification immediately before and after a project is evaluated. This can be used to do things like performing additional configuration once all the definitions in a build script have been applied, or for some custom logging or profiling.
Below is an example which adds a test
task to each project with the
hasTests
property set to true.
Example 37.6. Adding of test task to each project which has certain property set
build.gradle
allprojects { afterEvaluate { project -> if (project.hasTests) { println "Adding test task to $project" project.task('test') << { println "Running tests for $project" } } } }
projectA.gradle
hasTests = true
Output of gradle -q test
> gradle -q test Adding test task to project ':projectA' Running tests for project ':projectA'
This example uses method Project.afterEvaluate()
to add a closure which is executed
after the project is evaluated.
It is also possible to receive notifications when any project is evaluated. This example performs
some custom logging of project evaluation. Notice that the afterProject
notification
is received regardless of whether the project evaluates successfully or fails with an exception.
Example 37.7. Notifications
build.gradle
gradle.afterProject {project, projectState -> if (projectState.failure) { println "Evaluation of $project FAILED" } else { println "Evaluation of $project succeeded" } }
Output of gradle -q test
> gradle -q test Evaluation of root project 'buildProjectEvaluateEvents' succeeded Evaluation of project ':projectA' succeeded Evaluation of project ':projectB' FAILED
You can also add a ProjectEvaluationListener
to the
Gradle
to receive these events.
You can receive a notification immediately after a task is added to a project. This can be used to set some default values or add behaviour before the task is made available in the build file.
The following example sets the srcDir
property of each task as it is created.
Example 37.8. Setting of certain property to all tasks
build.gradle
tasks.whenTaskAdded { task -> task.srcDir = 'src/main/java' } task a println "source dir is $a.srcDir"
Output of gradle -q a
> gradle -q a source dir is src/main/java
You can also add an Action
to a
TaskContainer
to receive these events.
You can receive a notification immediately after the task execution graph has been populated. We have seen this already in Section 5.13, “Configure by DAG”.
You can also add a TaskExecutionGraphListener
to the
TaskExecutionGraph
to receive these events.
You can receive a notification immediately before and after any task is executed.
The following example logs the start and end of each task execution. Notice that the
afterTask
notification is received regardless of whether the task completes
successfully or fails with an exception.
Example 37.9. Logging of start and end of each task execution
build.gradle
task ok task broken(dependsOn: ok) << { throw new RuntimeException('broken') } gradle.taskGraph.beforeTask { Task task -> println "executing $task ..." } gradle.taskGraph.afterTask { Task task, TaskState state -> if (state.failure) { println "FAILED" } else { println "done" } }
Output of gradle -q broken
> gradle -q broken executing task ':ok' ... done executing task ':broken' ... FAILED
You can also use a TaskExecutionListener
to the
TaskExecutionGraph
to receive these events.
The powerful support for multi-project builds is one of Gradle's unique selling points. This topic is also the most intellectually challenging.
Let's start with a very simple multi-project build. After all Gradle is a general purpose build tool at its core, so the projects don't have to be java projects. Our first examples are about marine life.
We have the following project tree. This is a multi-project build with a root project
water
and a subproject bluewhale
.
Example 38.1. Multi-project tree - water & bluewhale projects
Build layout
water/ build.gradle settings.gradle bluewhale/
Note: The code for this example can be found at samples/userguide/multiproject/firstExample/water
which is in both the binary and source distributions of Gradle.
settings.gradle
include 'bluewhale'
And where is the build script for the bluewhale
project? In Gradle build scripts are optional.
Obviously for a single project build, a project without a build script doesn't make much sense. For
multiproject builds the situation is different. Let's look at the build script for the water
project and
execute it:
Example 38.2. Build script of water (parent) project
build.gradle
Closure cl = { task -> println "I'm $task.project.name" } task hello << cl project(':bluewhale') { task hello << cl }
Output of gradle -q hello
> gradle -q hello I'm water I'm bluewhale
Gradle allows you to access any project of the multi-project build from any build script. The Project
API provides a method called project()
, which takes a path as an argument and returns
the Project object for this path. The capability to configure a project build from any build script we
call cross project configuration. Gradle implements this via
configuration injection.
We are not that happy with the build script of the water
project. It is inconvenient to add the task
explicitly for every project. We can do better. Let's first add another project called
krill
to our multi-project build.
Example 38.3. Multi-project tree - water, bluewhale & krill projects
Build layout
water/ build.gradle settings.gradle bluewhale/ krill/
Note: The code for this example can be found at samples/userguide/multiproject/addKrill/water
which is in both the binary and source distributions of Gradle.
settings.gradle
include 'bluewhale', 'krill'
Now we rewrite the water
build script and boil it down to a single line.
Example 38.4. Water project build script
build.gradle
allprojects {
task hello << { task -> println "I'm $task.project.name" }
}
Output of gradle -q hello
> gradle -q hello I'm water I'm bluewhale I'm krill
Is this cool or is this cool? And how does this work? The Project API provides a property
allprojects
which returns a list with the current project and all its subprojects underneath it. If you call
allprojects
with a closure, the statements of the closure are delegated to the projects associated with
allprojects
. You could also do an iteration via allprojects.each
, but
that would be more verbose.
Other build systems use inheritance as the primary means for defining common behavior. We also offer inheritance for projects as you will see later. But Gradle uses configuration injection as the usual way of defining common behavior. We think it provides a very powerful and flexible way of configuring multiproject builds.
The Project API also provides a property for accessing the subprojects only.
Example 38.5. Defining common behaviour of all projects and subprojects
build.gradle
allprojects { task hello << {task -> println "I'm $task.project.name" } } subprojects { hello << {println "- I depend on water"} }
Output of gradle -q hello
> gradle -q hello I'm water I'm bluewhale - I depend on water I'm krill - I depend on water
You can add specific behavior on top of the common behavior. Usually we put the project specific
behavior in the build script of the project where we want to apply this specific behavior. But as we
have already seen, we don't have to do it this way. We could add project specific behavior for the
bluewhale
project like this:
Example 38.6. Defining specific behaviour for particular project
build.gradle
allprojects { task hello << {task -> println "I'm $task.project.name" } } subprojects { hello << {println "- I depend on water"} } project(':bluewhale').hello << { println "- I'm the largest animal that has ever lived on this planet." }
Output of gradle -q hello
> gradle -q hello I'm water I'm bluewhale - I depend on water - I'm the largest animal that has ever lived on this planet. I'm krill - I depend on water
As we have said, we usually prefer to put project specific behavior into the build script of this
project. Let's refactor and also add some project specific behavior to the krill
project.
Example 38.7. Defining specific behaviour for project krill
Build layout
water/ build.gradle settings.gradle bluewhale/ build.gradle krill/ build.gradle
Note: The code for this example can be found at samples/userguide/multiproject/spreadSpecifics/water
which is in both the binary and source distributions of Gradle.
settings.gradle
include 'bluewhale', 'krill'
bluewhale/build.gradle
hello.doLast { println "- I'm the largest animal that has ever lived on this planet." }
krill/build.gradle
hello.doLast {
println "- The weight of my species in summer is twice as heavy as all human beings."
}
build.gradle
allprojects { task hello << {task -> println "I'm $task.project.name" } } subprojects { hello << {println "- I depend on water"} }
Output of gradle -q hello
> gradle -q hello I'm water I'm bluewhale - I depend on water - I'm the largest animal that has ever lived on this planet. I'm krill - I depend on water - The weight of my species in summer is twice as heavy as all human beings.
To show more of the power of configuration injection, let's add another project
called tropicalFish
and add more behavior to the build via the build script of the
water
project.
Example 38.8. Adding custom behaviour to some projects (filtered by project name)
Build layout
water/ build.gradle settings.gradle bluewhale/ build.gradle krill/ build.gradle tropicalFish/
Note: The code for this example can be found at samples/userguide/multiproject/addTropical/water
which is in both the binary and source distributions of Gradle.
settings.gradle
include 'bluewhale', 'krill', 'tropicalFish'
build.gradle
allprojects { task hello << {task -> println "I'm $task.project.name" } } subprojects { hello << {println "- I depend on water"} } configure(subprojects.findAll {it.name != 'tropicalFish'}) { hello << {println '- I love to spend time in the arctic waters.'} }
Output of gradle -q hello
> gradle -q hello I'm water I'm bluewhale - I depend on water - I love to spend time in the arctic waters. - I'm the largest animal that has ever lived on this planet. I'm krill - I depend on water - I love to spend time in the arctic waters. - The weight of my species in summer is twice as heavy as all human beings. I'm tropicalFish - I depend on water
The configure()
method takes a list as an argument and applies the
configuration to the projects in this list.
Using the project name for filtering is one option. Using dynamic project properties is another.
Example 38.9. Adding custom behaviour to some projects (filtered by project properties)
Build layout
water/ build.gradle settings.gradle bluewhale/ build.gradle krill/ build.gradle tropicalFish/ build.gradle
Note: The code for this example can be found at samples/userguide/multiproject/tropicalWithProperties/water
which is in both the binary and source distributions of Gradle.
settings.gradle
include 'bluewhale', 'krill', 'tropicalFish'
bluewhale/build.gradle
arctic = true
hello.doLast { println "- I'm the largest animal that has ever lived on this planet." }
krill/build.gradle
arctic = true
hello.doLast {
println "- The weight of my species in summer is twice as heavy as all human beings."
}
tropicalFish/build.gradle
arctic = false
build.gradle
allprojects { task hello << {task -> println "I'm $task.project.name" } } subprojects { hello { doLast {println "- I depend on water"} afterEvaluate { Project project -> if (project.arctic) { doLast { println '- I love to spend time in the arctic waters.' } } } } }
Output of gradle -q hello
> gradle -q hello I'm water I'm bluewhale - I depend on water - I'm the largest animal that has ever lived on this planet. - I love to spend time in the arctic waters. I'm krill - I depend on water - The weight of my species in summer is twice as heavy as all human beings. - I love to spend time in the arctic waters. I'm tropicalFish - I depend on water
In the build file of the water
project we use an afterEvaluate
notification. This means that the closure we are passing gets evaluated after
the build scripts of the subproject are evaluated. As the property arctic
is set in those build scripts, we have to do it this way. You will find more on this topic in
Section 38.6, “Dependencies - Which dependencies?”
When we have executed the hello
task from the root project dir things behaved in an
intuitive way. All the hello
tasks of the different projects were executed. Let's switch
to the bluewhale
dir and see what happens if we execute Gradle from there.
Example 38.10. Running build from subproject
Output of gradle -q hello
> gradle -q hello I'm bluewhale - I depend on water - I'm the largest animal that has ever lived on this planet. - I love to spend time in the arctic waters.
The basic rule behind Gradle's behavior is simple. Gradle looks down the hierarchy, starting with the
current dir, for tasks with the name
hello
an executes them. One thing is very important to note. Gradle
always
evaluates
every
project of the multi-project build and creates all existing task objects. Then, according to the task name
arguments and the current dir, Gradle filters the tasks which should be executed. Because of Gradle's
cross project configuration every project has to be evaluated before any
task gets executed. We will have a closer look at this in the next section. Let's now have our last marine
example. Let's add a task to bluewhale
and krill
.
Example 38.11. Evaluation and execution of projects
bluewhale/build.gradle
arctic = true hello << { println "- I'm the largest animal that has ever lived on this planet." } task distanceToIceberg << { println '20 nautical miles' }
krill/build.gradle
arctic = true hello << { println "- The weight of my species in summer is twice as heavy as all human beings." } task distanceToIceberg << { println '5 nautical miles' }
Output of gradle -q distanceToIceberg
> gradle -q distanceToIceberg 20 nautical miles 5 nautical miles
Here the output without the -q
option:
Example 38.12. Evaluation and execution of projects
Output of gradle distanceToIceberg
> gradle distanceToIceberg :bluewhale:distanceToIceberg 20 nautical miles :krill:distanceToIceberg 5 nautical miles BUILD SUCCESSFUL Total time: 1 secs
The build is executed from the water
project. Neither water
nor
tropicalFish
have a task with the name distanceToIceberg
. Gradle does
not care. The simple rule mentioned already above is: Execute all tasks down the hierarchy which have this
name. Only complain if there is no such task!
As we have seen, you can run a multi-project build by entering any subproject dir and execute the build from there. All matching task names of the project hierarchy starting with the current dir are executed. But Gradle also offers to execute tasks by their absolute path (see also Section 38.5, “Project and task paths”):
Example 38.13. Running tasks by their absolute path
Output of gradle -q :hello :krill:hello hello
> gradle -q :hello :krill:hello hello I'm water I'm krill - I depend on water - The weight of my species in summer is twice as heavy as all human beings. - I love to spend time in the arctic waters. I'm tropicalFish - I depend on water
The build is executed from the tropicalFish
project. We execute the hello
tasks of the water
, the krill
and the tropicalFish
project. The first two tasks are specified by there absolute path, the last task is executed on the name
matching mechanism described above.
A project path has the following pattern: It starts always with a colon, which denotes the root project.
The root project is the only project in a path that is not specified by its name. The path
:bluewhale
corresponds to the file system path
water/bluewhale
in the case of the example above.
The path of a task is simply its project path plus the task name. For example
:bluewhale:hello
. Within a project you can address a task of the same project just by its name.
This is interpreted as a relative path.
Originally Gradle has used the
'/'
character as a natural path separator. With the introduction of directory tasks (see Section 12.1, “Directory creation”) this was no longer possible, as the name of the directory task
contains the
'/'
character.
The examples from the last section were special, as the projects had no Execution Dependencies. They had only Configuration Dependencies. Here is an example where this is different:
Example 38.14. Dependencies and execution order
Build layout
messages/ settings.gradle consumer/ build.gradle producer/ build.gradle
Note: The code for this example can be found at samples/userguide/multiproject/dependencies/firstMessages/messages
which is in both the binary and source distributions of Gradle.
settings.gradle
include 'consumer', 'producer'
consumer/build.gradle
task action << { println("Consuming message: " + (rootProject.hasProperty('producerMessage') ? rootProject.producerMessage : 'null')) }
producer/build.gradle
task action << { println "Producing message:" rootProject.producerMessage = 'Watch the order of execution.' }
Output of gradle -q action
> gradle -q action Consuming message: null Producing message:
This did not work out. If nothing else is defined, Gradle executes the task in alphanumeric order.
Therefore
:consumer:action
is executed before :producer:action
. Let's try to solve this with a hack and
rename the producer project to aProducer
.
Example 38.15. Dependencies and execution order
Build layout
messages/ settings.gradle aProducer/ build.gradle consumer/ build.gradle
settings.gradle
include 'consumer', 'aProducer'
aProducer/build.gradle
task action << { println "Producing message:" rootProject.producerMessage = 'Watch the order of execution.' }
consumer/build.gradle
task action << { println("Consuming message: " + (rootProject.hasProperty('producerMessage') ? rootProject.producerMessage : 'null')) }
Output of gradle -q action
> gradle -q action Producing message: Consuming message: Watch the order of execution.
Now we take the air out of this hack. We simply switch to the consumer
dir and
execute the build.
Example 38.16. Dependencies and execution order
Output of gradle -q action
> gradle -q action Consuming message: null
For Gradle the two
action
tasks are just not related. If you execute the build from the
messages
project Gradle executes them both because they have the same name and they are down the hierarchy.
In the last example only one
action
was down the hierarchy and therefore it was the only task that got executed. We need something
better than this hack.
Example 38.17. Declaring dependencies
Build layout
messages/ settings.gradle consumer/ build.gradle producer/ build.gradle
Note: The code for this example can be found at samples/userguide/multiproject/dependencies/messagesWithDependencies/messages
which is in both the binary and source distributions of Gradle.
settings.gradle
include 'consumer', 'producer'
consumer/build.gradle
dependsOn(':producer') task action << { println("Consuming message: " + (rootProject.hasProperty('producerMessage') ? rootProject.producerMessage : 'null')) }
producer/build.gradle
task action << { println "Producing message:" rootProject.producerMessage = 'Watch the order of execution.' }
Output of gradle -q action
> gradle -q action Producing message: Consuming message: Watch the order of execution.
Running this from the consumer
directory gives:
Example 38.18. Declaring dependencies
Output of gradle -q action
> gradle -q action Producing message: Consuming message: Watch the order of execution.
We have now declared that the
consumer
project has an
execution dependency
on the
producer
project. For Gradle declaring
execution dependencies
between
projects
is syntactic sugar. Under the hood Gradle creates task dependencies out of them. You can also create
cross project tasks dependencies manually by using the absolute path of the tasks.
Let's change the naming of our tasks and execute the build.
Example 38.19. Project execution dependencies
consumer/build.gradle
dependsOn(':producer') task consume << { println("Consuming message: " + (rootProject.hasProperty('producerMessage') ? rootProject.producerMessage : 'null')) }
producer/build.gradle
task produce << { println "Producing message:" rootProject.producerMessage = 'Watch the order of execution.' }
Output of gradle -q consume
> gradle -q consume Consuming message: null
Oops. Why does this not work? The
dependsOn
command is created for projects with a common lifecycle. Provided you have two Java projects where
one depends on the other. If you trigger a compile for the dependent project you don't want that
all
tasks of the other project get executed. Therefore a
dependsOn
creates dependencies between tasks with equal names. To deal with the scenario above you would do
the following:
Example 38.20. Cross project task dependencies
consumer/build.gradle
task consume(dependsOn: ':producer:produce') << { println("Consuming message: " + (rootProject.hasProperty('producerMessage') ? rootProject.producerMessage : 'null')) }
producer/build.gradle
task produce << { println "Producing message:" rootProject.producerMessage = 'Watch the order of execution.' }
Output of gradle -q consume
> gradle -q consume Producing message: Consuming message: Watch the order of execution.
Let's have one more example with our producer-consumer build before we enter Java land. We add a property to the producer project and create now a configuration time dependency from consumer on producer.
Example 38.21. Configuration time dependencies
consumer/build.gradle
message = rootProject.hasProperty('producerMessage') ? rootProject.producerMessage : 'null' task consume << { println("Consuming message: " + message) }
producer/build.gradle
rootProject.producerMessage = 'Watch the order of evaluation.'
Output of gradle -q consume
> gradle -q consume Consuming message: null
The default
evaluation
order of the projects is alphanumeric (for the same nesting level). Therefore the
consumer
project is evaluated before the
producer
project and the
key
value of the
producer
is set
after
it is read by the
consumer
project. Gradle offers a solution for this.
Example 38.22. Configuration time dependencies - evaluationDependsOn
consumer/build.gradle
evaluationDependsOn(':producer') message = rootProject.hasProperty('producerMessage') ? rootProject.producerMessage : 'null' task consume << { println("Consuming message: " + message) }
Output of gradle -q consume
> gradle -q consume Consuming message: Watch the order of evaluation.
The command
evaluationDependsOn
triggers the evaluation of
producer
before
consumer
is evaluated. The example is a bit contrived for the sake of showing the mechanism. In
this
case there would be an easier solution by reading the key property at execution time.
Example 38.23. Configuration time dependencies
consumer/build.gradle
task consume << { println("Consuming message: " + (rootProject.hasProperty('producerMessage') ? rootProject.producerMessage : 'null')) }
Output of gradle -q consume
> gradle -q consume Consuming message: Watch the order of evaluation.
Configuration dependencies are very different to execution dependencies. Configuration dependencies are between projects whereas execution dependencies are always resolved to task dependencies. Another difference is that always all projects are configured, even when you start the build from a subproject. The default configuration order is top down, which is usually what is needed.
On the same nesting level the configuration order depends on the alphanumeric position. The most
common use case is to have multi-project builds that share a common lifecycle (e.g. all projects use the
Java plugin). If you declare with
dependsOn
a
execution dependency
between different projects, the default behavior of this method is to create also a
configuration
dependency between the two projects. Therefore it is likely that you don't have to define configuration
dependencies explicitly.
Gradle's multi-project features are driven by real life use cases. The first example for describing such a use case, consists of two webapplication projects and a parent project that creates a distribution out of them. [18] For the example we use only one build script and do cross project configuration.
Example 38.24. Dependencies - real life example - crossproject configuration
Build layout
webDist/ settings.gradle build.gradle date/ src/main/java/ org/gradle/sample/ DateServlet.java hello/ src/main/java/ org/gradle/sample/ HelloServlet.java
Note: The code for this example can be found at samples/userguide/multiproject/dependencies/webDist
which is in both the binary and source distributions of Gradle.
settings.gradle
include 'date', 'hello'
build.gradle
dependsOnChildren() allprojects { apply plugin: 'java' group = 'org.gradle.sample' version = '1.0' } subprojects { apply plugin: 'war' repositories { mavenCentral() } dependencies { compile "javax.servlet:servlet-api:2.5" } } task explodedDist(dependsOn: assemble) << { File explodedDist = mkdir(buildDir, 'explodedDist') subprojects.each {project -> project.tasks.withType(Jar).each {archiveTask -> copy { from archiveTask.archivePath into explodedDist } } } }
We have an interesting set of dependencies. Obviously the
date
and
hello
projects have a
configuration
dependency on webDist
, as all the build logic for the webapp projects is injected by
webDist
. The
execution
dependency is in the other direction, as
webDist
depends on the build artifacts of
date
and hello
. There is even a third dependency.
webDist
has a
configuration
dependency on
date
and
hello
because it needs to know the archivePath
. But it asks for this information at
execution time. Therefore we have no circular dependency.
Such and other dependency patterns are daily bread in the problem space of multi-project builds. If a build system does not support such patterns, you either can't solve your problem or you need to do ugly hacks which are hard to maintain and massively afflict your productivity as a build master.
There is one more thing to note from the current example. We have used the command
dependsOnChildren()
. It is a convenience method and calls the
dependsOn
method of the parent project for every child project (not every sub project). It declares a
execution
dependency of
webDist
on
date
and hello
.
Another use case would be a situation where the subprojects have a configuration
and
execution dependency on the parent project. This is the case when the parent project does configuration
injection into its subprojects, and additionally produces something at execution time that is needed by
its child projects (e.g. code generation). In this case the parent project would call the
childrenDependOnMe
method to create an execution dependency for the child projects. We might add an example for this in a
future version of the user guide.
What if one projects needs the jar produced by another project in its compile path? And not just the jar but also the transitive dependencies of this jar? Obviously this is a very common use case for Java multi-project builds. As already mentioned in Section 34.3.4, “Project dependencies”, Gradle offers project lib dependencies for this.
Example 38.25. Project lib dependencies
Build layout
java/ settings.gradle build.gradle api/ src/main/java/ org/gradle/sample/ api/ Person.java apiImpl/ PersonImpl.java services/personService/ src/ main/java/ org/gradle/sample/services/ PersonService.java test/java/ org/gradle/sample/services/ PersonServiceTest.java shared/ src/main/java/ org/gradle/sample/shared/ Helper.java
Note: The code for this example can be found at samples/userguide/multiproject/dependencies/java
which is in both the binary and source distributions of Gradle.
We have the projects shared
, api
andpersonService
.
personService
has a lib dependency on the other two projects. api
has a lib dependency on shared
.
[19]
Example 38.26. Project lib dependencies
settings.gradle
include 'api', 'shared', 'services:personService'
build.gradle
subprojects { apply plugin: 'java' group = 'org.gradle.sample' version = '1.0' repositories { mavenCentral() } dependencies { testCompile "junit:junit:4.8.2" } } project(':api') { dependencies { compile project(':shared') } } project(':services:personService') { dependencies { compile project(':shared'), project(':api') } } dependsOnChildren()
All the build logic is in the
build.gradle
of the root project.
[20]
A lib
dependency is a special form of an execution dependency. It causes the other project to be built first and
adds the jar with the classes of the other project to the classpath. It also adds the dependencies of the
other project to the classpath. So you can enter the
api
directory and trigger a gradle compile
. First
shared
is built and then
api
is built. Project dependencies enable partial multi-project builds.
If you come from Maven land you might be perfectly happy with this. If you come from Ivy land, you might expect some more fine grained control. Gradle offers this to you:
Example 38.27. Fine grained control over dependencies
build.gradle
subprojects { apply plugin: 'java' group = 'org.gradle.sample' version = '1.0' } project(':api') { configurations { spi } dependencies { compile project(':shared') } task spiJar(type: Jar) { baseName = 'api-spi' dependsOn classes from sourceSets.main.classes include('org/gradle/sample/api/**') } artifacts { spi spiJar } } project(':services:personService') { dependencies { compile project(':shared') compile project(path: ':api', configuration: 'spi') testCompile "junit:junit:4.8.2", project(':api') } }
The Java plugin adds per default a jar to your project libraries which contains all the classes. In this
example we create an
additional
library containing only the interfaces of the
api
project. We assign this library to a new dependency configuration. For the person
service we declare that the project should be compiled only against the
api
interfaces but tested with all classes from api
.
The build
task of the Java plugin is typically used to compile, test, and perform
code style checks (if the CodeQuality plugin is used) of a single project. In multi-project builds
you may often want to do all of these tasks across a range of projects. The buildNeeded
and buildDependents
tasks can help with this.
Let's use the project structure shown in Example 38.26, “Project lib dependencies”. In this example :services:personservice depends on both :api and :shared. The :api project also depends on :shared.
Assume you are working on a single project, the :api project. You have been making changes, but
have not built the entire project since performing a clean. You want to build any necessary supporting
jars, but only perform code quality and unit tests on the project you have changed.
The build
task does this.
Example 38.28. Build and Test Single Project
Output of gradle :api:build
> gradle :api:build :shared:compileJava :shared:processResources :shared:classes :shared:jar :api:compileJava :api:processResources :api:classes :api:jar :api:assemble :api:compileTestJava :api:processTestResources :api:testClasses :api:test :api:check :api:build BUILD SUCCESSFUL Total time: 1 secs
While you are working in a typical development cycle repeatedly building and testing changes to
the :api project (knowing that you are only changing files in this one project), you may not want to
even suffer the expense of :shared:compile checking to see what has changed in the :shared project.
Adding the -a
option will cause gradle to use cached jars to resolve any project lib
dependencies and not try to re-build the depended on projects.
Example 38.29. Partial Build and Test Single Project
Output of gradle -a :api:build
> gradle -a :api:build :api:compileJava :api:processResources :api:classes :api:jar :api:assemble :api:compileTestJava :api:processTestResources :api:testClasses :api:test :api:check :api:build BUILD SUCCESSFUL Total time: 1 secs
If you have just gotten the latest version of source from your version control system which included changes
in other projects that :api depends on, you might want to not only build all the projects you depend on,
but test them as well. The buildNeeded
task also tests all the projects from the
project lib dependencies of the testRuntime configuration.
Example 38.30. Build and Test Depended On Projects
Output of gradle :api:buildNeeded
> gradle :api:buildNeeded :shared:compileJava :shared:processResources :shared:classes :shared:jar :api:compileJava :api:processResources :api:classes :api:jar :api:assemble :api:compileTestJava :api:processTestResources :api:testClasses :api:test :api:check :api:build :shared:assemble :shared:compileTestJava :shared:processTestResources :shared:testClasses :shared:test :shared:check :shared:build :api:buildNeeded BUILD SUCCESSFUL Total time: 1 secs
You also might want to refactor some part of the :api project that is used in other projects.
If you make these types of changes, it is not sufficient to test just the :api
project, you also need to test all projects that depend on the :api project.
The buildDependents
task also tests all the projects that have a project lib dependency
(in the testRuntime configuration) on the specified project.
Example 38.31. Build and Test Dependent Projects
Output of gradle :api:buildDependents
> gradle :api:buildDependents :shared:compileJava :shared:processResources :shared:classes :shared:jar :api:compileJava :api:processResources :api:classes :api:jar :api:assemble :api:compileTestJava :api:processTestResources :api:testClasses :api:test :api:check :api:build :services:personService:compileJava :services:personService:processResources :services:personService:classes :services:personService:jar :services:personService:assemble :services:personService:compileTestJava :services:personService:processTestResources :services:personService:testClasses :services:personService:test :services:personService:check :services:personService:build :api:buildDependents BUILD SUCCESSFUL Total time: 1 secs
Finally, you may want to build and test everything in all projects. If the root project has declared
dependsOnChildren()
(as this one does), then any task you run against the root project
will cause that same named task to be run on all the children. So you can just run
gradle build
to build and test all projects.
Properties and methods declared in a project are inherited to all its subprojects. This is an alternative to configuration injection. But we think that the model of inheritance does not reflect the problem space of multi-project builds very well. In a future edition of this user guide we might write more about this.
Method inheritance might be interesting to use as Gradle's Configuration Injection does not support methods yet (but will in a future release).
You might be wondering why we have implemented a feature we obviously don't like that much. One reason is that it is offered by other tools and we want to have the check mark in a feature comparison :). And we like to offer our users a choice.
Writing this chapter was pretty exhausting and reading it might have a similar effect. Our final message
for this chapter is that multi-project builds with Gradle are usually
not
difficult. There are six elements you need to remember: allprojects
,
subprojects
, dependsOn
, childrenDependOnMe
,
dependsOnChildren
and project lib dependencies.
[21]
With those elements, and keeping in mind that Gradle has a distinct configuration and execution phase, you
have already a lot of flexibility. But when you enter steep territory Gradle does not become an obstacle and
usually accompanies and carries you to the top of the mountain.
[18] The real use case we had, was using http://lucene.apache.org/solr, where you need a separate war for each index your are accessing. That was one reason why we have created a distribution of webapps. The Resin servlet container allows us, to let such a distribution point to a base installation of the servlet container.
[19]
services
is also a project, but we use it just as a container. It has no build script and gets nothing
injected by another build script.
[20] We do this here, as it makes the layout a bit easier. We usually put the project specific stuff into the build script of the respective projects.
[21] So we are well in the range of the 7 plus 2 Rule :)
Gradle supports two types of task. One such type is the simple task, where you define the task with an action closure. We have seen these in Chapter 5, Build Script Basics. For this type of task, the action closure determines the behaviour of the task. This type of task is good for implementing one-off tasks in your build script.
The other type of task is the enhanced task, where the behaviour is built into the task, and the task provides some properties which you can use to configure the behaviour. We have seen these in Chapter 14, More about Tasks. Most Gradle plugins use enhanced tasks. With enhanced tasks, you don't need to implement the task behaviour as you do with simple tasks. You simply declare the task and configure the task using its properties. In this way, enhanced tasks let you reuse a piece of behaviour in many different places, possibly across different builds.
The behaviour and properties of an enhanced task is defined by the task's class. When you declare an enhanced task, you specify the type, or class of the task.
Implementing your own custom task class in Gradle is easy. You can implement a custom task class in pretty much any language you like, provided it ends up compiled to bytecode. In our examples, we are going to use Groovy as the implementation language, but you could use, for example, Java or Scala. In general, using Groovy is the easiest option, because the Gradle API is designed to work well with Groovy.
There are several places where you can put the source for the task class.
You can include the task class directly in the build script. This has the benefit that the task class is automatically compiled and included in the classpath of the build script without you having to do anything. However, the task class is not visible outside the build script, and so you cannot reuse the task class outside the build script it is defined in.
buildSrc
projectYou can put the source for the task class in the
directory.
Gradle will take care of compiling and testing the task class and making it available on the
classpath of the build script. The task class is visible to every build script used by the build.
However, it is not visible outside the build, and so you cannot reuse the task class outside the
build it is defined in.
Using the rootProjectDir
/buildSrc/src/main/groovybuildSrc
project approach keeps separate
the task declaration - that is, what the task should do - from the task implementation - that is,
how the task does it.
See Chapter 41, Organizing Build Logic for more details about the buildSrc
project.
You can create a separate project for your task class. This project produces and publishes a JAR which you can then use in multiple builds and share with others. Generally, this JAR might include some custom plugins, or bundle several related task classes into a single library. Or some combination of the two.
In our examples, we will start with the task class in the build script, to keep things simple. Then we will look at creating a standalone project.
To implement a custom task class, you extend DefaultTask
.
This task doesn't do anything useful, so let's add some behaviour. To do so, we add a method to the task
and mark it with the TaskAction
annotation. Gradle will call the
method when the task executes. You don't have to use a method to define the behaviour for the task. You
could, for instance, call doFirst()
or doLast()
with a closure in the
task constructor to add behaviour.
Example 39.2. A hello world task
build.gradle
task hello(type: GreetingTask) class GreetingTask extends DefaultTask { @TaskAction def greet() { println 'hello from GreetingTask' } }
Output of gradle -q hello
> gradle -q hello hello from GreetingTask
Let's add a property to the task, so we can customize it. Tasks are simply POGOs, and when you declare a
task, you can set the properties or call methods on the task object. Here we add a greeting
property, and set the value when we declare the greeting
task.
Example 39.3. A customizable hello world task
build.gradle
// Use the default greeting task hello(type: GreetingTask) // Customize the greeting task greeting(type: GreetingTask) { greeting = 'greetings from GreetingTask' } class GreetingTask extends DefaultTask { def String greeting = 'hello from GreetingTask' @TaskAction def greet() { println greeting } }
Output of gradle -q hello greeting
> gradle -q hello greeting hello from GreetingTask greetings from GreetingTask
Now we will move our task to a standalone project, so we can publish it and share it with others. This project is simply a Groovy project that produces a JAR containing the task class. Here is a simple build script for the project. It applies the Groovy plugin, and adds the Gradle API as a compile-time dependency.
Example 39.4. A build for a custom task
build.gradle
apply plugin: 'groovy'
dependencies {
compile gradleApi()
}
Note: The code for this example can be found at samples/customPlugin
which is in both the binary and source distributions of Gradle.
We just follow the convention for where the source for the task class should go.
Example 39.5. A custom task
src/main/groovy/org/gradle/GreetingTask.groovy
package org.gradle import org.gradle.api.DefaultTask import org.gradle.api.tasks.TaskAction class GreetingTask extends DefaultTask { String greeting = 'hello from GreetingTask' @TaskAction def greet() { println greeting } }
To use a task class in a build script, you need to add the class to the build script's classpath. To
do this, you use a buildscript { }
block, as described in Section 41.5, “External dependencies for the build script”.
The following example shows how you might do this when the JAR containing the task class has been published
to a local repository:
Example 39.6. Using a custom task in another project
usesCustomTask.gradle
buildscript { repositories { mavenRepo urls: uri('repo') } dependencies { classpath group: 'org.gradle', name: 'customPlugin', version: '1.0-SNAPSHOT' } } task greeting(type: org.gradle.GreetingTask) { greeting = 'howdy!' }
You can use the ProjectBuilder
class to create
Project
instances to use when you test your task class.
Example 39.7. Testing a custom task
src/test/groovy/org/gradle/GreetingTaskTest.groovy
class GreetingTaskTest { @Test public void canAddTaskToProject() { Project project = ProjectBuilder.builder().build() def task = project.task('greeting', type: GreetingTask) assertTrue(task instanceof GreetingTask) } }
A Gradle plugin packages up reusable pieces of build logic, which can be used across many different projects and builds. Gradle allows you to implement your own custom plugins, so you can reuse your build logic, and share it with others.
You can implement a custom plugin in any language you like, provided the implementation ends up compiled as bytecode. For the examples here, we are going to use Groovy as the implementation language. You could use Java or Scala instead, if you want.
There are several places where you can put the source for the plugin.
You can include the source for the plugin directly in the build script. This has the benefit that the plugin is automatically compiled and included in the classpath of the build script without you having to do anything. However, the plugin is not visible outside the build script, and so you cannot reuse the plugin outside the build script it is defined in.
buildSrc
projectYou can put the source for the plugin in the
directory.
Gradle will take care of compiling and testing the plugin and making it available on the
classpath of the build script. The plugin is visible to every build script used by the build.
However, it is not visible outside the build, and so you cannot reuse the plugin outside the
build it is defined in.
rootProjectDir
/buildSrc/src/main/groovy
See Chapter 41, Organizing Build Logic for more details about the buildSrc
project.
You can create a separate project for your plugin. This project produces and publishes a JAR which you can then use in multiple builds and share with others. Generally, this JAR might include some custom plugins, or bundle several related task classes into a single library. Or some combination of the two.
In our examples, we will start with the plugin in the build script, to keep things simple. Then we will look at creating a standalone project.
To create a custom plugin, you need to write an implementation of Plugin
.
Gradle instantiates the plugin and calls the plugin instance's Plugin.apply()
method when the
plugin is used with a project. The project
object is passed as a parameter, which the plugin can use to configure the project however it needs to.
The following sample contains a greeting plugin, which adds a hello
task to the project.
Example 40.1. A custom plugin
build.gradle
apply plugin: GreetingPlugin class GreetingPlugin implements Plugin<Project> { def void apply(Project project) { project.task('hello') << { println "Hello from the GreetingPlugin" } } }
Output of gradle -q hello
> gradle -q hello Hello from the GreetingPlugin
One thing to note is that a new instance of a given plugin is created for each project it is applied to.
Most plugins need to obtain some configuration from the build script. One method for doing this is to use convention objects.
The Gradle Project
has a Convention
object
that helps keep track of all the settings and properties being passed to plugins. You can capture user input by telling
the Project Convention about your plugin. To capture input, simply add a Java Bean compliant class into the Convention's list of
plugins. Groovy is a good language choice for a plugin because plain old Groovy objects contain all the getter and setter methods
that a Java Bean requires.
Let's add a simple convention object to the project. Here we add a greeting
property to the
project, which allows you to configure the greeting.
Example 40.2. A custom plugin convention
build.gradle
apply plugin: GreetingPlugin greeting = 'Hi from Gradle' class GreetingPlugin implements Plugin<Project> { def void apply(Project project) { project.convention.plugins.greet = new GreetingPluginConvention() project.task('hello') << { println project.convention.plugins.greet.greeting } } } class GreetingPluginConvention { def String greeting = 'Hello from GreetingPlugin' }
Output of gradle -q hello
> gradle -q hello Hi from Gradle
In this example, GreetingPluginConvention
is a plain old Groovy object with a field called greeting
.
The convention object is added to the plugin list with the name greet
. The name of the variable in
the build needs to match the name of the field in the convention object. The name you choose for your plugin
(greet
) is arbitrary and can be whatever you choose.
Oftentimes, you have several related properties you need to specify on a single plugin. With Groovy plugins it is easy to offer a configuration closure block to group settings together. The following example shows you how to do this.
Example 40.3. A custom plugin with closure convention
build.gradle
apply plugin: GreetingPlugin greet { message = 'Hi from Gradle' } class GreetingPlugin implements Plugin<Project> { def void apply(Project project) { project.convention.plugins.greet = new GreetingPluginConvention() project.task('hello') << { println project.convention.plugins.greet.message } } } class GreetingPluginConvention { String message def greet(Closure closure) { closure.delegate = this closure() } }
Output of gradle -q hello
> gradle -q hello Hi from Gradle
In this example, several convention settings can be grouped together within the greet
closure.
The name of the closure block in the build script (greet
) needs a matching method on
the convention object, and that method must take a closure as an argument. Then, when the closure is executed,
the fields on the convention object will be mapped to the variables within the closure based on the standard
Groovy closure delegate feature. This technique is possible in other JVM languages but may not be as convenient
as in Groovy.
Now we will move our plugin to a standalone project, so we can publish it and share it with others. This project is simply a Groovy project that produces a JAR containing the plugin classes. Here is a simple build script for the project. It applies the Groovy plugin, and adds the Gradle API as a compile-time dependency.
Example 40.4. A build for a custom plugin
build.gradle
apply plugin: 'groovy'
dependencies {
compile gradleApi()
}
Note: The code for this example can be found at samples/customPlugin
which is in both the binary and source distributions of Gradle.
So how does Gradle find the Plugin
implementation? The answer is you need to provide a properties file in the jar's
META-INF/gradle-plugins
directory that matches the name of your plugin.
Example 40.5. Wiring for a custom plugin
src/main/resources/META-INF/gradle-plugins/greeting.properties
implementation-class=org.gradle.GreetingPlugin
Notice that the properties filename matches the plugin's name and is placed in the resources folder, and
that the implementation-class
property identifies the Plugin
implementation class.
To use a plugin in a build script, you need to add the plugin classes to the build script's classpath. To
do this, you use a buildscript { }
block, as described in Section 41.5, “External dependencies for the build script”.
The following example shows how you might do this when the JAR containing the plugin has been published
to a local repository:
Example 40.6. Using a custom plugin in another project
usesCustomPlugin.gradle
buildscript { repositories { mavenRepo urls: uri('repo') } dependencies { classpath group: 'org.gradle', name: 'customPlugin', version: '1.0-SNAPSHOT' } } apply plugin: 'greeting'
You can use the ProjectBuilder
class to create
Project
instances to use when you test your plugin implementation.
Example 40.7. Testing a custom plugin
src/test/groovy/org/gradle/GreetingPluginTest.groovy
class GreetingPluginTest { @Test public void greeterPluginAddsGreetingTaskToProject() { Project project = ProjectBuilder.builder().build() project.apply plugin: 'greeting' assertTrue(project.tasks.hello instanceof GreetingTask) } }
Gradle provides some utility classes for maintaining collections of object, which work well with the Gradle build language.
Example 40.8. Managing domain objects
build.gradle
apply plugin: DocumentationPlugin books { quickStart { sourceFile = file('src/docs/quick-start') } userGuide { } developerGuide { } } task books << { books.each { book -> println "$book.name -> $book.sourceFile" } } class DocumentationPlugin implements Plugin<Project> { def void apply(Project project) { def books = project.container(Book) { name -> new Book(name) } books.all { sourceFile = project.file("src/docs/$name") } project.convention.plugins.documentation = new DocumentationPluginConvention(books) } } class Book { final String name File sourceFile Book(String name) { this.name = name } } class DocumentationPluginConvention { final NamedDomainObjectContainer<Book> books DocumentationPluginConvention(NamedDomainObjectContainer<Book> books) { this.books = books } def books(Closure cl) { books.configure(cl) } }
Output of gradle -q books
> gradle -q books developerGuide -> /home/user/gradle/samples/userguide/organizeBuildLogic/customPluginWithDomainObjectContainer/src/docs/developerGuide quickStart -> /home/user/gradle/samples/userguide/organizeBuildLogic/customPluginWithDomainObjectContainer/src/docs/quick-start userGuide -> /home/user/gradle/samples/userguide/organizeBuildLogic/customPluginWithDomainObjectContainer/src/docs/userGuide
Gradle offers a variety of ways to organize your build logic. First of all you can put your build logic directly in the action closure of a task. If a couple of tasks share the same logic you can extract this logic into a method. If multiple projects of a multi-project build share some logic you can define this method in the parent project. If the build logic gets too complex for being properly modeled by methods you want have an OO Model. [22] Gradle makes this very easy. Just drop your classes in a certain directory and Gradle automatically compiles them and puts them in the classpath of your build script.
Here is a summary of the ways you can organise your build logic:
POGOs. You can declare and use plain old Groovy objects (POGOs) directly in your build script. The build script is written in Groovy, after all, and Groovy provides you with lots of excellent ways to organize code.
Inherited properties and methods. In a multi-project build, sub-projects inherit the properties and methods of their parent project.
Configuration injection. In a multi-project build, a project (usually the root project) can inject properties and methods into another project.
buildSrc
project. Drop the source for
your build classes into a certain directory and Gradle automatically compiles them and includes them
in the classpath of your build script.
Shared scripts. Define common configuration in an external build, and apply the script to multiple projects, possibly across different builds.
Custom tasks. Put your build logic into a custom task, and reuse that task in multiple places.
Custom plugins. Put your build build logic into a custom plugin,
and apply that plugin to multiple projects. The plugin must be in the classpath of your build script.
You can achieve this either by using build sources
or
by adding an external library that contains the plugin.
Execute an external build. Execute another Gradle build from the current build.
External libraries. Use external libraries directly in your build file.
Any method or property defined in a project build script is also visible to all the sub-projects. You can use this to define common configurations, and to extract build logic into methods which can be reused by the sub-projects.
Example 41.1. Using inherited properties and methods
build.gradle
srcDirName = 'src/java' def getSrcDir(project) { return project.file(srcDirName) }
child/build.gradle
task show << { // Use inherited property println 'srcDirName: ' + srcDirName // Use inherited method File srcDir = getSrcDir(project) println 'srcDir: ' + rootProject.relativePath(srcDir) }
Output of gradle -q show
> gradle -q show srcDirName: src/java srcDir: child/src/java
You can use the configuration injection technique discussed in Section 38.1, “Cross project configuration” and Section 38.2, “Subproject configuration” to inject properties and methods into various projects. This is generally a better option than inheritance, for a number of reasons: The injection is explicit in the build script, You can inject different logic into different projects, And you can inject any kind of configuration such as repositories, plug-ins, tasks, and so on. The following sample shows how this works.
Example 41.2. Using injected properties and methods
build.gradle
subprojects { // Inject a property and method srcDirName = 'src/java' srcDir = { file(srcDirName) } // Inject a task task show << { println 'project: ' + project.path println 'srcDirName: ' + srcDirName File srcDir = srcDir() println 'srcDir: ' + rootProject.relativePath(srcDir) } } // Inject special case configuration into a particular project project(':child2') { srcDirName = "$srcDirName/legacy" }
child1/build.gradle
// Use injected property and method. Here, we override the injected value srcDirName = 'java' def dir = srcDir()
Output of gradle -q show
> gradle -q show project: :child1 srcDirName: java srcDir: child1/java project: :child2 srcDirName: src/java/legacy srcDir: child2/src/java/legacy
If you run Gradle, it checks for the existence of a directory called buildSrc
. Just put
your build source code in this directory and stick to the layout convention for a Java/Groovy project (see
Table 20.4, “Java plugin - default project layout”). Gradle then automatically compiles and tests this code and puts it in
the classpath of your build script. You don't need to provide any further instruction. This can be a good
place to add your custom tasks and plugins.
For multi-project builds there can be only one buildSrc
directory, which has to be
in the root project.
This is probably good enough for most of the cases. If you need more flexibility, you can provide a
build.gradle
and a settings.gradle
file in the
buildSrc
directory. If you like, you can even have a multi-project build in there.
You can use the GradleBuild
task. You can use either of the
dir
or buildFile
properties to specify which build to execute,
and the tasks
property to specify which tasks to execute.
Example 41.3. Running another build from a build
build.gradle
task build(type: GradleBuild) { buildFile = 'other.gradle' tasks = ['hello'] }
other.gradle
task hello << {
println "hello from the other build."
}
Output of gradle -q build
> gradle -q build hello from the other build.
If your build script needs to use external libraries, you can add them to the script's classpath in the
build script itself. You do this using the buildscript()
method, passing in a closure which
declares the build script classpath.
Example 41.4. Declaring external dependencies for the build script
build.gradle
buildscript { repositories { mavenCentral() } dependencies { classpath group: 'commons-codec', name: 'commons-codec', version: '1.2' } }
The closure passed to the buildscript()
method configures a
ScriptHandler
instance. You declare the build script
classpath by adding dependencies to the classpath
configuration. This is the same way
you declare, for example, the Java compilation classpath. You can use any of the dependency types described
in Section 34.3, “How to declare your dependencies”, except project dependencies.
Having declared the build script classpath, you can use the classes in your build script as you would any other classes on the classpath. The following example adds to the previous example, and uses classes from the build script classpath.
Example 41.5. A build script with external dependencies
build.gradle
import org.apache.commons.codec.binary.Base64 buildscript { repositories { mavenCentral() } dependencies { classpath group: 'commons-codec', name: 'commons-codec', version: '1.2' } } task encode << { def byte[] encodedString = new Base64().encode('hello world\n'.getBytes()) println new String(encodedString) }
Output of gradle -q encode
> gradle -q encode aGVsbG8gd29ybGQK
For multi-project builds, the dependencies declared in the a project's build script, are available to the build scripts of all sub-projects.
For reasons we don't fully understand yet, external dependencies are not picked up by Ant's optional tasks. But you can easily do it in another way. [23]
Example 41.6. Ant optional dependencies
build.gradle
configurations { ftpAntTask } dependencies { ftpAntTask("org.apache.ant:ant-commons-net:1.8.2") { module("commons-net:commons-net:1.4.1") { dependencies "oro:oro:2.0.8:jar" } } } task ftp << { ant { taskdef(name: 'ftp', classname: 'org.apache.tools.ant.taskdefs.optional.net.FTP', classpath: configurations.ftpAntTask.asPath) ftp(server: "ftp.apache.org", userid: "anonymous", password: "me@myorg.com") { fileset(dir: "htdocs/manual") } } }
This is also nice example for the usage of client modules. The pom.xml in maven central for the ant-commons-net task does not provide the right information for this use case.
Gradle offers you a variety of ways of organizing your build logic. You can choose what is right for your domain and find the right balance between unnecessary indirections, and avoiding redundancy and a hard to maintain code base. It is our experience that even very complex custom build logic is rarely shared between different builds. Other build tools enforce a separation of this build logic into a separate project. Gradle spares you this unnecessary overhead and indirection.
[22] Which might range from a single class to something very complex.
[23] In fact, we think this is anyway the nicer solution. Only if your buildscript and Ant's optional
task need the same library you would have to define it two times. In such a
case it would be nice, if Ant's optional task would automatically pickup the classpath defined
in the gradesettings
.
Gradle provides a powerful mechanism to allow customizing the build based on the current environment. This mechanism also supports tools that wish to integrate with Gradle.
Initialization scripts (a.k.a. init scripts) are similar to other scripts in Gradle. These scripts, however, are run before the build starts. Here are several possible uses:
Set up properties based on the current environment (such as a developer's machine vs. a continuous integration server).
Supply personal information about the user to the build, such as repository or database authentication credentials.
Define machine specific details, such as where JDKs are installed.
Register build listeners. External tools that wish to listen to Gradle events might find this useful.
Register build loggers. You might wish to customise how Gradle logs the events that it generates.
One main limitation of init scripts is that they cannot access classes in the buildSrc project (see
Section 41.3, “Build sources in the buildSrc
project” for details of this feature).
There are two ways to use init scripts. Either put a file called init.gradle
in
,
or specify the file on the command line. The command line option is USER_HOME
/.gradle-I
or
--init-script
followed by the path to the script. The command line option can appear
more than once, each time adding another init script. If more than one init script is found they will all be
executed. This allows for a tool to specify an init script and the user to put home in their home directory
for defining the environment and both scripts will run when gradle is executed.
Similar to a Gradle build script, an init script is a groovy script. Each init script has a
Gradle
instance associated with it. Any property reference
and method call in the init script will delegate to this Gradle
instance.
Each init script also implements the Script
interface.
In Section 41.5, “External dependencies for the build script” is was explained how to add external dependencies to a
build script. Init scripts can similarly have external dependencies defined. You do this using the
initscript()
method, passing in a closure which declares the init script classpath.
Example 42.1. Declaring external dependencies for an init script
init.gradle
initscript { repositories { mavenCentral() } dependencies { classpath group: 'org.apache.commons', name: 'commons-math', version: '2.0' } }
The closure passed to the initscript()
method configures a
ScriptHandler
instance. You declare the init script
classpath by adding dependencies to the classpath
configuration. This is the same way
you declare, for example, the Java compilation classpath. You can use any of the dependency types described
in Section 34.3, “How to declare your dependencies”, except project dependencies.
Having declared the init script classpath, you can use the classes in your init script as you would any other classes on the classpath. The following example adds to the previous example, and uses classes from the init script classpath.
Example 42.2. An init script with external dependencies
init.gradle
import org.apache.commons.math.fraction.Fraction initscript { repositories { mavenCentral() } dependencies { classpath group: 'org.apache.commons', name: 'commons-math', version: '2.0' } } println Fraction.ONE_FIFTH.multiply(2)
Output of gradle --init-script init.gradle -q doNothing
> gradle --init-script init.gradle -q doNothing 2 / 5
Gradle is a new tool. You can't expect it to be installed on machines beyond your sphere of influence. An example are continuous integration server where Gradle is not installed and where you have no admin rights for the machine. Or what if you provide an open source project and you want to make it as easy as possible for your users to build it?
There is a simple and good Wrapper
task.
[24]
You can create such a task in your build script.
The build master usually explicitly executes this task. After such an execution you find the following new or updated files in your project directory (in case the default configuration of the wrapper task is used).
Example 43.2. Wrapper generated files
Build layout
simple/ gradlew gradlew.bat gradle/wrapper/ gradle-wrapper.jar gradle-wrapper.properties
All these files must be submitted to your version control system. The gradlew command can be used exactly the same way as the gradle command.
If you want to switch to a new version of Gradle you don't need to rerun the wrapper task. It is good enough
to change the respective entry in the gradle-wrapper.properties
file. But if there is for
example an improvement in the gradle-wrapper functionality you need to regenerate the wrapper files.
If you run Gradle with gradlew, Gradle checks if a Gradle distribution for the wrapper is available. If not it tries to download it, otherwise it delegates to the gradle command of this distribution with all the arguments passed originally to the gradlew command.
You can specify where the wrapper files should be stored (within your project directory):
Example 43.3. Configuration of wrapper task
build.gradle
task wrapper(type: Wrapper) { gradleVersion = '0.9' jarFile = 'wrapper/wrapper.jar' }
Build layout
customized/ gradlew gradlew.bat wrapper/ wrapper.jar wrapper.properties
You can specify the download URL of the wrapper distribution. You can also specify where the wrapper distribution should be stored and unpacked (either within the project or within the gradle user home dir). If the wrapper is run and there is local archive of the wrapper distribution Gradle tries to download it and stores it at the specified place. If there is no unpacked wrapper distribution Gradle unpacks the local archive of the wrapper distribution at the specified place. All the configuration options have defaults except the version of the wrapper distribution.
For the details on how to configure the wrapper, see Wrapper
If you don't want any download to happen when your project is build via gradlew, simply add the Gradle distribution zip to your version control at the location specified by your wrapper configuration.
If you build via the wrapper, any existing Gradle distribution installed on the machine is ignored.
The Wrapper task adds appropriate file permissions to allow the execution for the gradlew *NIX command.
Subversion preserves this file permission. We are not sure how other version control systems deal with this.
What should always work is to execute sh gradlew
.
Some rather exotic use cases might occur when working with the Gradle Wrapper. For example the continuos integration server goes down during unzipping the Gradle distribution. As the distribution directory exists gradlew delegates to it but the distribution is corrupt. Or the zip-distribution was not properly downloaded. When you have no admin right on the continuous integration server to remove the corrupt files, Gradle offers a solution via environment variables.
Table 43.1. Gradle wrapper environment variables
Variable Name | Meaning |
GRADLE_WRAPPER_ALWAYS_UNPACK | If set to true , the distribution directory gets always deleted when
gradlew
is run and the distribution zip is freshly unpacked. If the zip is not there, Gradle tries to
download it.
|
GRADLE_WRAPPER_ALWAYS_DOWNLOAD | If set to true , the distribution directory and the distribution zip gets always
deleted when gradlew
is run and the distribution zip is freshly downloaded.
|
[24] If you download the Gradle source distribution or check out Gradle from SVN, you can build Gradle via the Gradle wrapper. Gradle itself is continuously built by Bamboo and Teamcity via this wrapper. See http://www.gradle.org/ci-server.html
Listed below are some of the stand-alone samples which are included in the Gradle distribution. You can find these samples in the
directory of the distribution.GRADLE_HOME
/samples
Table A.1. Samples included in the distribution
Sample | Description |
announce
|
A project which uses the announce plugin |
application
|
A project which uses the application plugin |
codeQuality
|
A project which uses the code quality plugin. |
customBuildLanguage
|
This sample demonstrates how to add some custom elements to the build DSL. It also demonstrates the use of custom plug-ins to organize build logic. |
customPlugin
|
A project which implements a custom plugin and task. |
groovy/customizedLayout
|
Groovy project with a custom source layout |
groovy/groovy-1.5.6
|
Groovy project using Groovy 1.5.6 |
groovy/groovy-1.6.7
|
Groovy project using Groovy 1.6.7 |
groovy/mixedJavaAndGroovy
|
Project containing a mix of Java and Groovy source |
groovy/multiproject
|
Build made up of multiple Groovy projects. Also demonstrates how to exclude certain source files, and the use of a custom Groovy AST transformation. |
groovy/quickstart
|
Groovy quickstart sample |
java/base
|
Java base project |
java/customizedLayout
|
Java project with a custom source layout |
java/multiproject
|
This sample demonstrates how an application can be composed using multiple Java projects. |
java/quickstart
|
Java quickstart project |
java/withIntegrationTests
|
This sample demonstrates how to use a source set to add an integration test suite to a Java project. |
maven/pomGeneration
|
Demonstrates how to deploy and install to a Maven repository. Also demonstrates how to deploy a javadoc JAR along with the main JAR, how to customize the contents of the generated POM, and how to deploy snapshots and releases to different repositories. |
maven/quickstart
|
Demonstrates how to deploy and install artifacts to a Maven repository. |
osgi
|
A project which builds an OSGi bundle |
scala/customizedLayout
|
Scala project with a custom source layout |
scala/fsc
|
Sala project using the Fast Scala Compiler (fsc). |
scala/mixedJavaAndScala
|
A project containing a mix of Java and Scala source. |
scala/quickstart
|
Scala quickstart project |
toolingApi/build
|
An application which uses the tooling API to execute a Gradle build. |
toolingApi/model
|
An application which uses the tooling API to build the model for a project. |
webApplication/customised
|
Web application with customized WAR contents. |
webApplication/quickstart
|
Web application quickstart project |
This sample demonstrates how to add some custom elements to the build DSL. It also demonstrates the use of custom plug-ins to organize build logic.
The build is composed of 2 types of projects. The first type of project represents a product, and the second represents a product module. Each product includes one or more product modules, and each product module may be included in multiple products. That is, there is a many-to-many relationship between these products and product modules. For each product, the build produces a ZIP containing the runtime classpath for each product module included in the product. The ZIP also contains some product-specific files.
The custom elements can be seen in the build script for the product projects (for example,
basicEdition/build.gradle
). Notice that the build script uses the
product { }
element. This is a custom element.
The build scripts of each project contain only declarative elements. The bulk of the work is done by 2
custom plug-ins found in buildSrc/src/main/groovy
.
This sample demonstrates how an application can be composed using multiple Java projects.
This build creates a client-server application which is distributed as 2 archives. First, there is a client ZIP which includes an API JAR, which a 3rd party application would compile against, and a client runtime. Then, there is a server WAR which provides a web service.
For Gradle users it is important to understand how Groovy deals with script variables. Groovy has two types of script variables. One with a local scope and one with a script wide scope.
Example B.1. Variables scope: local and script wide
scope.groovy
String localScope1 = 'localScope1' def localScope2 = 'localScope2' scriptScope = 'scriptScope' println localScope1 println localScope2 println scriptScope closure = { println localScope1 println localScope2 println scriptScope } def method() { try {localScope1} catch(MissingPropertyException e) {println 'localScope1NotAvailable' } try {localScope2} catch(MissingPropertyException e) {println 'localScope2NotAvailable' } println scriptScope } closure.call() method()
Output of gradle
> gradle localScope1 localScope2 scriptScope localScope1 localScope2 scriptScope localScope1NotAvailable localScope2NotAvailable scriptScope
Variables which are declared with a type modifier are visible within closures but not visible within methods. This is a heavily discussed behavior in the Groovy community. [25]
It is important to keep in mind that Gradle has a distinct configuration and execution phase (see Chapter 37, The Build Lifecycle).
Example B.2. Distinct configuration and execution phase
build.gradle
classesDir = file('build/classes') classesDir.mkdirs() task clean(type: Delete) { delete 'build' } task compile(dependsOn: 'clean') << { if (!classesDir.isDirectory()) { println 'The class directory does not exist. I can not operate' // do something } // do something }
Output of gradle -q compile
> gradle -q compile The class directory does not exist. I can not operate
As the creation of the directory happens during the configuration phase, the
clean
task removes the directory during the execution phase.
[25] One of those discussions can be found here: http://www.nabble.com/script-scoping-question-td16034724.html
The gradle command has the following usage:
gradle
[option...] [task...]
The command-line options available for the gradle command are listed below:
-?
, -h
, --help
Shows a help message.
-C
, --cache
Specifies how compiled build scripts should be cached. Possible values are:
rebuild
or on
. Default value is
on
. See Section 12.7, “Caching”.
-D
, --system-prop
Sets a system property of the JVM, for example -Dmyprop=myvalue
.
-I
, --init-script
Specifies an initialization script. See Chapter 42, Initialization Scripts.
-P
, --project-prop
Sets a project property of the root project, for example
-Pmyprop=myvalue
.
-S
, --full-stacktrace
Print out the full (very verbose) stacktrace for any exceptions. See Chapter 16, Logging.
-a
, --no-rebuild
Do not rebuild project dependencies.
--all
Shows additional detail in the task listing. See Section 10.5.2, “Listing tasks”.
-b
, --build-file
Specifies the build file. See Section 10.4, “Selecting which build to execute”.
-c
, --settings-file
Specifies the settings file.
-d
, --debug
Log in debug mode (includes normal stacktrace). See Chapter 16, Logging.
-e
, --embedded
Specify an embedded build script.
-g
, --gradle-user-home
Specifies the Gradle user home directory.
--gui
Launches the Gradle GUI. See Chapter 11, Using the Gradle Graphical User Interface.
-i
, --info
Set log level to info. See Chapter 16, Logging.
-m
, --dry-run
Runs the build with all task actions disabled.
--no-color
Do not use color in the console output.
-p
, --project-dir
Specifies the start directory for Gradle. Defaults to current directory. See Section 10.4, “Selecting which build to execute”.
--profile
Profiles build execution time and generates a report in the <build_dir>/reports/profile directory.
-q
, --quiet
Log errors only. See Chapter 16, Logging.
-s
, --stacktrace
Print out the stacktrace also for user exceptions (e.g. compile error). See Chapter 16, Logging.
-u
, --no-search-upwards
Don't search in parent directories for a settings.gradle
file.
-v
, --version
Prints version info.
-x
, --exclude-task
Specifies a task to be excluded from execution. See Section 10.2, “Excluding tasks”.
The above information is printed to the console when you execute gradle -h
.
The following options are deprecated and will be removed in a future version of Gradle:
-n
, --dependencies
(deprecated) Show list of all project dependencies. You should use gradle dependencies
instead. See Section 10.5.3, “Listing project dependencies”.
-r
, --properties
(deprecated) Show list of all available project properties. You should use gradle properties
instead. See Section 10.5.4, “Listing project properties”.
-t
, --tasks
(deprecated) Show list of available tasks. You should use gradle tasks
instead. See Section 10.5.2, “Listing tasks”.
The following options are experimental:
--daemon
Uses the Gradle daemon to run the build. Starts the daemon if not running.
--foreground
Starts the Gradle daemon in the foreground.
--no-daemon
Do not use the Gradle daemon to run the build.
--stop
Stops the Gradle daemon if it is running.
The following system properties are available for the gradle command. Note that command-line options take precedence over system properties.
gradle.user.home
Specifies the Gradle user home directory.
org.gradle.daemon
When set to true
, use the Gradle daemon to run the build.
The following environment variables are available for the gradle command. Note that command-line options and system properties take precedence over environment variables.
GRADLE_OPTS
Specifies command-line arguments to use to start the JVM. This can be useful for setting
the system properties to use for running Gradle. For example you could set GRADLE_OPTS="-Dorg.gradle.daemon=true"
to use the Gradle daemon without needing to use the --daemon
option every time you
run Gradle.
GRADLE_USER_HOME
Specifies the Gradle user home directory.
Gradle has been mainly developed with Idea IntelliJ and its very good Groovy plugin. Gradle's build script
[26]
has also been developed with the support of this IDE. IntelliJ allows you to define any filepattern to be
interpreted as a Groovy script. In the case of Gradle you can define such a pattern for
build.gradle
and settings.gradle
. This will already help very much. What is missing is the classpath
to the Gradle binaries to offer content assistance for the Gradle classes. You might add the Gradle jar
(which you can find in your distribution) to your project's classpath. It does not really belong there, but
if you do this you have a fantastic IDE support for developing Gradle scripts. Of course if you use
additional libraries for your build scripts they would further pollute your project classpath.
We hope that in the future *.gradle
files
get special treatment by IntelliJ and you will be able to define a specific classpath for them.
There is a Groovy plugin for eclipse. We don't know in what state it is and how it would support Gradle. In the next edition of this user guide we can hopefully write more about this.
What we can do for you is to spare you typing things like
throw new org.gradle.api.tasks.StopExecutionException()
and just type
throw new StopExecutionException()
instead. We do this by automatically adding a set of import statements to the Gradle scripts before Gradle
executes them. Listed below are the imports added to each script.
Figure D.1. gradle-imports
import org.gradle.* import org.gradle.util.* import org.gradle.api.* import org.gradle.api.artifacts.* import org.gradle.api.artifacts.dsl.* import org.gradle.api.artifacts.maven.* import org.gradle.api.artifacts.specs.* import org.gradle.api.execution.* import org.gradle.api.file.* import org.gradle.api.initialization.* import org.gradle.api.invocation.* import org.gradle.api.java.archives.* import org.gradle.api.logging.* import org.gradle.api.plugins.* import org.gradle.plugins.ide.eclipse.* import org.gradle.plugins.ide.idea.* import org.gradle.api.plugins.quality.* import org.gradle.api.specs.* import org.gradle.api.tasks.* import org.gradle.api.tasks.bundling.* import org.gradle.api.tasks.diagnostics.* import org.gradle.api.tasks.compile.* import org.gradle.api.tasks.javadoc.* import org.gradle.api.tasks.testing.* import org.gradle.api.tasks.util.* import org.gradle.api.tasks.wrapper.* import org.gradle.process.*
A directed acyclic graph is a directed graph that contains no cycles. In Gradle each task to execute represents a node in the graph. A dependsOn relation to another task will add this other task as a node (if it is not in the graph already) and create a directed edge between those two nodes. Any dependsOn relation will be validated for cycles. There must be no way to start at certain node, follow a sequence of edges and end up at the original node.
A domain-specific language is a programming language or specification language dedicated to a particular problem domain, a particular problem representation technique, and/or a particular solution technique. The concept isn't new—special-purpose programming languages and all kinds of modeling/specification languages have always existed, but the term has become more popular due to the rise of domain-specific modeling.