# Chapter 24. The Groovy Plugin

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. [9] 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.

## 24.1. Usage

To use the Groovy plugin, include in your build script:

Example 24.1. Using the Groovy plugin

`build.gradle`

    apply plugin: 'groovy'

## 24.2. Tasks

The Groovy plugin adds the following tasks to the project.

Table 24.1. 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`SourceSet`Groovy` | `compile`SourceSet`Java` | `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 24.2. Groovy plugin - additional task dependencies

Task name | Depends on
classes | compileGroovy
testClasses | compileTestGroovy
`sourceSet`Classes | compile`SourceSet`Groovy

Figure 24.1. Groovy plugin - tasks

## 24.3. Project layout

The Groovy plugin assumes the project layout shown in Table 24.3, “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. [10] 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 24.3. 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/`sourceSet`/java` | Java source for the given source set
`src/`sourceSet`/resources` | Resources for the given source set
`src/`sourceSet`/groovy` | Groovy source for the given source set. May also contain Java source for joint compilation.

### 24.3.1. Changing the project layout

TBD

Example 24.2. Custom Groovy source layout

`build.gradle`

    sourceSets {
        main {
            groovy {
                srcDir 'src/groovy'
            }
        }
    }

## 24.4. Dependency management

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 `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 24.3. 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 24.4. Configuration of Groovy plugin

`build.gradle`

    repositories {
        flatDir { dirs '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')
            }
        }
    }

## 24.5. Convention properties

The Groovy plugin does not add any convention properties to the project.

## 24.6. Source set properties

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 21.3, “Conventions”).

Table 24.4. 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 16.5, “Specifying a set of input files”. | `[`projectDir`/src/`name`/groovy]` | 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 24.5. 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.

## 24.7. CompileGroovy

The Groovy plugin adds a `GroovyCompile` instance for each source set in the project. The task type extends the `Compile` task (see Section 23.11, “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 24.6. Groovy plugin - CompileGroovy properties

Task Property | Type | Default Value
`classpath` | `FileCollection` | ``sourceSet`.compileClasspath`
`source` | `FileTree`. Can set using anything described in Section 16.5, “Specifying a set of input files”. | ``sourceSet`.groovy`
`destinationDir` | `File`. | ``sourceSet`.output.classesDir`
`groovyClasspath` | `FileCollection` | `groovy` configuration

[9] 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.

[10] We are using the same conventions as introduced by Russel Winders Gant tool (http://gant.codehaus.org).