Protobuf Plugin for Gradle
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README.md

❗️ Starting from version 0.7.6, the plugin requires Gradle 2.12 and later. Please check your Gradle version if you see the following error:

Error:Unable to load class 'org.gradle.api.internal.file.collections.DefaultDirectoryFileTreeFactory'.

❗️ Please read release notes before upgrading the plugin.

Protobuf Plugin for Gradle Status

The Gradle plugin that compiles Protocol Buffer (aka. Protobuf) definition files (*.proto) in your project. There are two pieces of its job:

  1. It assembles the Protobuf Compiler (protoc) command line and use it to generate Java source files out of your proto files.
  2. It adds the generated Java source files to the input of the corresponding Java compilation unit (sourceSet in a Java project; variant in an Android project), so that they can be compiled along with your Java sources.

For more information about the Protobuf Compiler, please refer to Google Developers Site.

Latest Version

The latest version is 0.8.6. It requires at least Gradle 2.12 and Java 7. It is available on Maven Central. To add dependency to it:

buildscript {
  repositories {
    mavenCentral()
  }
  dependencies {
    classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.6'
  }
}

To try out the head version, you can download the source and build it with ./gradlew install -x test (we skip tests here because they require Android SDK), then:

buildscript {
  repositories {
    mavenLocal()
  }
  dependencies {
    classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.6-SNAPSHOT'
  }
}

Examples

A stand-alone example project is located under exampleProject. Run ../gradlew build under that directory to test it out.

Directories that start with testProject can also serve as usage examples for advanced options, although they cannot be compiled as individual projects.

Adding the plugin to your project

This plugin must work with either the Java plugin or the Android plugin.

Using the apply method

The Java plugin or the Android plugin must be applied before the Protobuf plugin:

apply plugin: 'java'
apply plugin: 'com.google.protobuf'
apply plugin: 'com.android.application'  // or 'com.android.library'
apply plugin: 'com.google.protobuf'

The experimental Android plugin is not supported yet (#85).

Using the Gradle plugin DSL

The order of the plugins doesn't matter:

plugins {
  id "com.google.protobuf" version "0.8.6"
  id "java"
}

Configuring Protobuf compilation

The Protobuf plugin assumes Protobuf files (*.proto) are organized in the same way as Java source files, in sourceSets. The Protobuf files of a sourceSet (or variant in an Android project) are compiled in a single protoc run, and the generated files are added to the input of the Java compilation run of that sourceSet (or variant).

Customizing source directories

The plugin adds a new sources block named proto alongside java to every sourceSet. By default, it includes all *.proto files under src/$sourceSetName/proto. You can customize it in the same way as you would customize the java sources.

Java projects: use the top-level sourceSet:

sourceSets {
  main {
    proto {
      // In addition to the default 'src/main/proto'
      srcDir 'src/main/protobuf'
      srcDir 'src/main/protocolbuffers'
      // In addition to the default '**/*.proto' (use with caution).
      // Using an extension other than 'proto' is NOT recommended,
      // because when proto files are published along with class files, we can
      // only tell the type of a file from its extension.
      include '**/*.protodevel'
    }
    java {
      ...
    }
  }
  test {
    proto {
      // In addition to the default 'src/test/proto'
      srcDir 'src/test/protocolbuffers'
    }
  }
}

Android projects: use android.sourceSets:

android {
  sourceSets {
    main {
      proto {
        ...
      }
      java {
        ...
      }
    }
  }
}

Customizing Protobuf compilation

The plugin adds a protobuf block to the project. It provides all the configuration knobs.

Locate external executables

By default the plugin will search for the protoc executable in the system search path. We recommend you to take the advantage of pre-compiled protoc that we have published on Maven Central:

protobuf {
  ...
  // Configure the protoc executable
  protoc {
    // Download from repositories
    artifact = 'com.google.protobuf:protoc:3.0.0'
  }
  ...
}

You may also specify a local path.

protobuf {
  ...
  protoc {
    path = '/usr/local/bin/protoc'
  }
  ...
}

Multiple assignments are allowed in the protoc block. The last one wins.

You may also run protoc with codegen plugins. You need to define all the codegen plugins you will use in the plugins block, by specifying the downloadable artifact or a local path, in the same syntax as in the protoc block above. This will not apply the plugins. You need to configure the tasks in the generateProtoTasks block introduced below to apply the plugins defined here.

protobuf {
  ...
  // Configure the codegen plugins
  plugins {
    // Define a plugin with name 'grpc'
    grpc {
      artifact = 'io.grpc:protoc-gen-grpc-java:1.0.0-pre2'
      // or
      // path = 'tools/protoc-gen-grpc-java'
    }
    // Any other plugins
    ...
  }
  ...
}

The syntax for artifact follows Artifact Classifiers where the default classifier is project.osdetector.classifier (ie "${project.osdetector.os}-${project.osdetector.arch}") and the default extension is "exe". Non-C++ implementations of codegen plugins can be used if a constant classifier is specified (eg "com.example:example-generator:1.0.0:-jvm8_32").

Customize code generation tasks

The Protobuf plugin generates a task for each protoc run, which is for a sourceSet in a Java project, or a variant in an Android project. The task has configuration interfaces that allow you to control the type of outputs, the codegen plugins to use, and parameters.

You must configure these tasks in the generateProtoTasks block, which provides you helper functions to conveniently access tasks that are tied to a certain build element, and also ensures you configuration will be picked up correctly by the plugin.

DONOTs:

  • DO NOT assume the names of the tasks, as they may change.
  • DO NOT configure the tasks outside of the generateProtoTasks block, because there are subtle timing constraints on when the tasks should be configured.
protobuf {
  ...
  generateProtoTasks {
    // all() returns the collection of all protoc tasks
    all().each { task ->
      // Here you can configure the task
    }

    // In addition to all(), you may select tasks by various criteria:

    // (Java-only) returns tasks for a sourceSet
    ofSourceSet('main')

    // (Android-only selectors)
    // Returns tasks for a flavor
    ofFlavor('demo')
    // Returns tasks for a buildType
    ofBuildType('release')
    // Returns tasks for a variant
    ofVariant('demoRelease')
    // Returns non-androidTest tasks
    ofNonTest()
    // Return androidTest tasks
    ofTest()
  }
}

Each code generation task has two collections:

  • builtins: code generators built in protoc, e.g., java, cpp, python.
  • plugins: code generation plugins that work with protoc, e.g., grpc. They must be defined in the protobuf.plugins block in order to be added to a task.

Configure what to generate

Code generation is done by protoc builtins and plugins. Each builtin/plugin generate a certain type of code. To add or configure a builtin/plugin on a task, list its name followed by a braces block. Put options in the braces if wanted. For example:

task.builtins {
  // This yields
  // "--java_out=example_option1=true,example_option2:/path/to/output"
  // on the protoc commandline, which is equivalent to
  // "--java_out=/path/to/output --java_opt=example_option1=true,example_option2"
  // with the latest version of protoc.
  java {
    option 'example_option1=true'
    option 'example_option2'
  }
  // Add cpp output without any option.
  // DO NOT omit the braces if you want this builtin to be added.
  // This yields
  // "--cpp_out=/path/to/output" on the protoc commandline.
  cpp { }
}

task.plugins {
  // Add grpc output without any option.  grpc must have been defined in the
  // protobuf.plugins block.
  // This yields
  // "--grpc_out=/path/to/output" on the protoc commandline.
  grpc { }
}

Default outputs

Java projects: the java builtin is added by default: without any further specification, Java classes will be generated during the build process.

Python output can be generated by adding the python builtin:

protobuf {
  generatedFilesDir = "$projectDir/generated"

  generateProtoTasks {
    all().each { task ->
      task.builtins {
        // Generates Python code in the output folder:
        python { }

        // If you wish to avoid generating Java files:
        remove java
      }
    }
  }
}

See this section for details about where the code will be generated.

Android projects: no default output will be added. Since Protobuf 3.0.0, protobuf-lite is the recommended Protobuf library for Android, and you will need to add it as a codegen plugin. For example:

dependencies {
  // You need to depend on the lite runtime library, not protobuf-java
  compile 'com.google.protobuf:protobuf-lite:3.0.0'
}

protobuf {
  protoc {
    // You still need protoc like in the non-Android case
    artifact = 'com.google.protobuf:protoc:3.0.0'
  }
  plugins {
    javalite {
      // The codegen for lite comes as a separate artifact
      artifact = 'com.google.protobuf:protoc-gen-javalite:3.0.0'
    }
  }
  generateProtoTasks {
    all().each { task ->
      task.builtins {
        // In most cases you don't need the full Java output
        // if you use the lite output.
        remove java
      }
      task.plugins {
        javalite { }
      }
    }
  }
}

Generate descriptor set files

{ task ->
  // If true, will generate a descriptor_set.desc file under
  // $generatedFilesBaseDir/$sourceSet. Default is false.
  // See --descriptor_set_out in protoc documentation about what it is.
  task.generateDescriptorSet = true

  // Allows to override the default for the descriptor set location
  task.descriptorSetOptions.path =
    "${projectDir}/build/descriptors/{$task.sourceSet.name}.dsc"

  // If true, the descriptor set will contain line number information
  // and comments. Default is false.
  task.descriptorSetOptions.includeSourceInfo = true

  // If true, the descriptor set will contain all transitive imports and
  // is therefore self-contained. Default is false.
  task.descriptorSetOptions.includeImports = true
}

Change where files are generated

By default generated Java files are under $generatedFilesBaseDir/$sourceSet/$builtinPluginName, where $generatedFilesBaseDir is $buildDir/generated/source/proto by default, and is configurable. E.g.,

protobuf {
  ...
  generatedFilesBaseDir = "$projectDir/src/generated"
}

The subdirectory name, which is by default $builtinPluginName, can also be changed by setting the outputSubDir property in the builtins or plugins block of a task configuration within generateProtoTasks block (see previous section). E.g.,

{ task ->
  task.plugins {
    grpc {
      // Write the generated files under
      // "$generatedFilesBaseDir/$sourceSet/grpcjava"
      outputSubDir = 'grpcjava'
    }
  }
}

Protos in dependencies

If a Java project contains proto files, they will be packaged in the jar files along with the compiled classes. If a compile configuration has a dependency on a project or library jar that contains proto files, they will be added to the --proto_path flag of the protoc command line, so that they can be imported in the proto files of the dependent project. The imported proto files will not be compiled since they have already been compiled in their own projects. Example:

dependencies {
  compile project(':someProjectWithProtos')
  testCompile files("lib/some-testlib-with-protos.jar")
}

If there is a project, package or published artifact that contains just protos files, whose compiled classes are absent, and you want to use these proto files in your project and compile them, you can add it to protobuf dependencies. Example:

dependencies {
  protobuf files('lib/protos.tar.gz')
  testProtobuf 'com.example:published-protos:1.0.0'
}

Pre-compiled protoc artifacts

This Maven Central directory lists pre-compiled protoc artifacts that can be used by this plugin.

Tips for IDEs

IntelliJ IDEA

Be sure to enable delegate IDE build/run actions to Gradle so that Intellij does not use its internal build mechanism to compile source code. This plugin ensures that code generation happens before Gradle's build step. If the setting is off, Intellij's own build system will be used instead of Gradle.

Enable the setting with:

Settings -> Build, Execution, Deployment
  -> Build Tools -> Gradle -> Runner
  -> Delegate IDE build/run actions to gradle.

This plugin integrates with the idea plugin and automatically registers the proto files and generated Java code as sources.

apply plugin: 'idea'

protobuf {
    ...
    generatedFilesBaseDir = "$projectDir/gen"
}

clean {
    delete protobuf.generatedFilesBaseDir
}

idea {
    module {
        // proto files and generated Java files are automatically added as
        // source dirs.
        // If you have additional sources, add them here:
        sourceDirs += file("/path/to/other/sources");
    }
}

Testing the plugin

testProject* are testing projects that uses this plugin to compile .proto files. Because the tests include an Android project, you need to install Android SDK Tools.

After you made any change to the plugin, be sure to run these tests.

$ ./gradlew test