Chapter 29. The Eclipse Plugin

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 tasks.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 executing gradle cleanEclipseClasspath eclipseClasspath.

A complete overwrite causes all existing content to be discarded, thereby losing any changes made directly in the IDE. The beforeMerged 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:

eclipse.classpath.file {
    beforeMerged { 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:

eclipse.project.file.beforeMerged { project ->
    project.natures.clear()
}

The whenMerged 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:

eclipse.classpath.file {
    whenMerged { classpath ->
        classpath.entries.findAll { entry -> entry.kind == 'lib' }*.exported = false
    }
}

The withXmlhook 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.

apply plugin: 'eclipse-wtp'

eclipse.wtp.facet.file.withXml { provider ->
    provider.asNode().fixed.find { it.@facet == 'jst.java' }.@facet = 'jst2.java'
}