Chapter 36. The Eclipse Plugin

The Eclipse plugin generates files that are used by the Eclipse IDE, thus making it possible to import the project into Eclipse (File - Import... - Existing Projects into Workspace). Both external dependencies (including associated source and javadoc files) and project dependencies are considered.

Since 1.0-milestone-4 WTP-generating code was refactored into a separate plugin called eclipse-wtp. So if you are interested in WTP integration then only apply the eclipse-wtp plugin. Otherwise applying eclipse plugin is enough. This change was requested by Eclipse users who take advantage of war or ear plugin but they don't use Eclipse WTP. Internally, eclipse-wtp also applies the eclipse plugin so you don't need to apply both of those plugins.

What exactly the Eclipse plugin generates depends on which other plugins are used:

Table 36.1. Eclipse plugin behavior

NoneGenerates minimal .project file.
JavaAdds Java configuration to .project. Generates .classpath and JDT settings file.
GroovyAdds Groovy configuration to .project file.
ScalaAdds Scala support to .project and .classpath files.
WarAdds web application support to .project file. Generates WTP settings files only if eclipse-wtp plugin was applied.
EarAdds ear application support to .project file. Generates WTP settings files only if eclipse-wtp plugin was applied.

The Eclipse plugin is open to customization and provides a standardized set of hooks for adding and removing content from the generated files.

36.1. Usage

To use the Eclipse plugin, include this in your build script:

Example 36.1. Using the Eclipse plugin


apply plugin: 'eclipse'

The Eclipse plugin adds a number of tasks to your projects. The main tasks that you will use are the eclipse and cleanEclipse tasks.

36.2. Tasks

The Eclipse plugin adds the tasks shown below to a project.

Table 36.2. 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 Removes the .project file.
cleanEclipseClasspath - Delete Removes 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 - GenerateEclipseProject Generates the .project file.
eclipseClasspath - GenerateEclipseClasspath Generates the .classpath file.
eclipseJdt - GenerateEclipseJdt Generates the .settings/org.eclipse.jdt.core.prefs file.
eclipseWtpComponent - GenerateEclipseWtpComponent Generates the .settings/org.eclipse.wst.common.component file only if eclipse-wtp plugin was applied.
eclipseWtpFacet - GenerateEclipseWtpFacet Generates the .settings/org.eclipse.wst.common.project.facet.core.xml file only if eclipse-wtp plugin was applied.

36.3. Configuration

Table 36.3. Configuration of the Eclipse plugin

Model Reference name Description
EclipseModel eclipse Top level element that enables configuration of the Eclipse plugin in a DSL-friendly fashion
EclipseProject eclipse.project Allows configuring project information
EclipseClasspath eclipse.classpath Allows configuring classpath information
EclipseJdt eclipse.jdt Allows configuring jdt information (source/target java compatibility)
EclipseWtpComponent eclipse.wtp.component Allows configuring wtp component information only if eclipse-wtp plugin was applied.
EclipseWtpFacet eclipse.wtp.facet Allows configuring wtp facet information only if eclipse-wtp plugin was applied.

36.4. Customizing the generated files

The Eclipse plugin allows you to customise the generated metadata files. The plugin provides a DSL for configuring model objects that model the Eclipse view of the project. These model objects are then merged with the existing Eclipse XML metadata to ultimately generate new metadata. The model objects provide lower level hooks for working with domain objects representing the file content before and after merging with the model configuration. They also provide a very low level hook for working directly with the raw XML for adjustment before it is persisted, for fine tuning and configuration that the Eclipse plugin does not model.

36.4.1. Merging

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. Disabling merging with a complete overwrite

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.

36.4.2. Hooking into the generation lifecycle

The Eclipse plugin provides objects modeling the sections of the Eclipse files that are generated by Gradle. The generation lifecycle is as follows:

  1. The file is read; or a default version provided by Gradle is used if it does not exist
  2. The beforeMerged hook is executed with a domain object representing the existing file
  3. The existing content is merged with the configuration inferred from the Gradle build or defined explicitly in the eclipse DSL
  4. The whenMerged hook is executed with a domain object representing contents of the file to be persisted
  5. The withXml hook is executed with a raw representation of the xml that will be persisted
  6. The final XML is persisted

The following table lists the domain object used for each of the Eclipse model types:

Table 36.4. Advanced configuration hooks

Model beforeMerged { arg -> } argument type whenMerged { arg -> } argument type withXml { arg -> } argument type
EclipseProject Project Project XmlProvider
EclipseClasspath Classpath Classpath XmlProvider
EclipseJdt Jdt Jdt
EclipseWtpComponent WtpComponent WtpComponent XmlProvider
EclipseWtpFacet WtpFacet WtpFacet XmlProvider Partial overwrite of existing content

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

Example 36.2. Partial Overwrite for Classpath


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:

Example 36.3. Partial Overwrite for Project


eclipse.project.file.beforeMerged { project ->
} Modifying the fully populated domain objects

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:

Example 36.4. Export Dependencies


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

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.

Example 36.5. Customizing the XML


apply plugin: 'eclipse-wtp'

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