gradle-apt-plugin

This plugin does a few things to make it easier/safer to use Java annotation processors in a Gradle build:

it adds configurations for your compile-time only dependencies (annotations, generally) and annotation processors;
automatically configures the corresponding JavaCompile and GroovyCompile tasks to make use of these configurations, when the java or groovy plugin is applied;
automatically configures IntelliJ IDEA and/or Eclipse when the idea or eclipse plugins are applied.

Using the plugin

The plugin is published to the Plugin Portal; see instructions there: https://plugins.gradle.org/plugin/net.ltgt.apt

Added configurations

The following configurations are added to any Java project:

compileOnly, extends compile
apt
testCompileOnly, extends testCompile
testApt

The *Only configurations are used to specify compile-time only dependencies such as annotations that will be processed by annotation processors. Annotation processors themselves are to be added to the apt and testApt configurations.

The *Only configurations are part of the classpath of the JavaCompile and GroovyCompile tasks, whereas the apt and testApt configurations are turned into -processorpath compiler arguments. Note that if those configurations are empty, an empty processor path (-processorpath :) will be passed to javac; this is a breaking change compared to the normal behavior of Gradle, as it means annotation processors won't be looked up in the tasks' classpath.

Example usage

After applying the plugin following the above instructions, those added configurations can be used when declaring dependencies:

dependencies {
  compile "com.google.dagger:dagger:2.0.2"
  apt     "com.google.dagger:dagger-compiler:2.0.2"

  // auto-factory contains both annotations and their processor, neither is needed at runtime
  compileOnly "com.google.auto.factory:auto-factory:1.0-beta3"
  apt         "com.google.auto.factory:auto-factory:1.0-beta3"
}

Groovy support

Starting with version 0.6, the plugin also configures GroovyCompile tasks added when the groovy plugin is applied. It does not however configure annotation processing for Groovy sources, only for Java sources used in joint compilation. Turn process annotations on Groovy sources, you'll have to configure your GroovyCompile tasks; e.g.

compileGroovy {
  groovyOptions.javaAnnotationProcessing = true
}

Usage with IDEs

When the idea or eclipse plugins are applied, the idea and eclipse tasks will auto-configure the generated files to enable annotation processing in the corresponding IDE.

When using the Gradle integration in IntelliJ IDEA however, rather than the idea task, you'll have to manually enable annotation processing: in Settings… → Build, Execution, Deployment → Compiler → Annotation Processors, check Enable annotation processing and Obtain processors from project classpath. To mimic the Gradle behavior and generated files behavior, you can configure the production and test sources directories to build/generated/source/apt/main and build/generated/source/apt/test respectively and choose to Store generated sources relative to: Module content root.

jkuipers / gradle-apt-plugin