Protobuf Plugin for Gradle
The Gradle plugin that compiles Protocol Buffer (aka. Protobuf) definition
files (*.proto
) in your project. There are two pieces of its job:
- It assembles the Protobuf Compiler (
protoc
) command line and uses it to generate Java source files out of your proto files. - 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.
- Note if you are generating non-Java/Kotlin source files, they will not be included for compilation automatically, you will need to add them to sources for language-specific compilations. See details in Default options section.
For more information about the Protobuf Compiler, please refer to Google Developers Site.
Latest Version
The latest version is 0.9.4
. It requires at least Gradle 5.6 and Java 8.
To use it with Groovy DSL:
plugins {
id "com.google.protobuf" version "0.9.4"
}
Development Version
To try out the head version, you can download the source and build it
with ./gradlew publishToMavenLocal -x test
(we skip tests here because they
require Android SDK), then in settings.gradle
:
pluginManagement {
repositories {
gradlePluginPortal()
mavenLocal()
}
}
And in build.gradle
:
plugins {
id "com.google.protobuf" version "0.10.0-SNAPSHOT"
}
Examples
Stand-alone examples are available for each of gradle's supported languages.
- Groovy (Default)
- Run
../../gradlew build
under the example directory to test it out.
- Run
- Kotlin (Experimental)
- Run
./gradlew build
under the Kotlin example directory to test it out. This example is set up with Gradle 4.10, the minimum required version.
- Run
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.
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. For a codegen
plugin named as "foo", protoc
will by default use
protoc-gen-foo
from system search path. You can also specify a
downloadable artifact or a local path for it in the plugins
block,
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 {
...
// Locate the codegen plugins
plugins {
// Locate a plugin with name 'grpc'. This step is optional.
// If you leave it empty, it uses the current directory.
// If you don't specify it, protoc will try to use "protoc-gen-grpc" from
// system search path.
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().configureEach { 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 inprotoc
, e.g.,java
,cpp
,python
.plugins
: code generation plugins that work withprotoc
, e.g.,grpc
. They must be defined in theprotobuf.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 generates 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 {
generateProtoTasks {
all().configureEach { task ->
task.builtins {
// Generates Python code
python { }
// If you wish to avoid generating Java files:
remove java
}
}
}
}
Note the generated Python code will not be included for compilation, you will need to add them as sources to Python's compilation tasks manually. 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, the lite runtime is the recommended Protobuf library for Android.
For Protobuf versions from 3.0.x through 3.7.x, lite code generation is provided as a protoc plugin (protobuf-lite). Example:
dependencies {
// You need to depend on the lite runtime library, not protobuf-java
implementation '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:3.7.0'
}
plugins {
javalite {
// The codegen for lite comes as a separate artifact
artifact = 'com.google.protobuf:protoc-gen-javalite:3.0.0'
}
}
generateProtoTasks {
all().configureEach { 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 { }
}
}
}
}
Starting from Protobuf 3.8.0, lite code generation is built into protoc's "java" output. Example:
dependencies {
// You need to depend on the lite runtime library, not protobuf-java
implementation 'com.google.protobuf:protobuf-javalite:3.8.0'
}
protobuf {
protoc {
artifact = 'com.google.protobuf:protoc:3.8.0'
}
generateProtoTasks {
all().configureEach { task ->
task.builtins {
java {
option "lite"
}
}
}
}
}
Generate descriptor set files
{ task ->
// If true, will generate a descriptor_set.desc file under
// task.outputBaseDir. 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
Generated files are under task.outputBaseDir
with a subdirectory per
builtin and plugin. This produces a folder structure of
$buildDir/generated/source/proto/$sourceSet/$builtinPluginName
.
The subdirectory name, which is by default $builtinPluginName
, can 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 {
// Use subdirectory 'grpcjava' instead of the default 'grpc'
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.
Protos in dependencies (e.g. upstream jars) can be put in either in the compile
configuration or the protobuf
configuration.
If the dependency is put in the compile
configuration, the proto files are
extracted to an extracted-include-protos
directory and added to the --proto_path
flag of the protoc command line, so that they can be imported by the proto files
of the current project. The imported proto files will not be compiled since
they have already been compiled in their own projects. Example:
dependencies {
implementation project(':someProjectWithProtos')
testImplementation files("lib/some-testlib-with-protos.jar")
}
If the dependency is put in the protobuf
configuration, the proto files are
extracted to a extracted-protos
directory and added to the protoc command
line as files to compile, in the same protoc invocation as the current project's
proto files (if any). Example:
dependencies {
// protos can be from a local package,
protobuf files('lib/protos.tar.gz')
// ... a local directory,
protobuf files('ext/') // NEVER use fileTree(). See issue #248.
// ... or an artifact from a repository
testProtobuf 'com.example:published-protos:1.0.0'
}
protoc
artifacts
Pre-compiled 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.
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