sbt plugin for compiling protobuf files
Scala Protocol Buffer
Latest commit 6bce04a Apr 10, 2017 @xuwei-k xuwei-k add multi-project example


A plugin for sbt that transforms *.proto files into gazillion-loc Java source files, and potentially to other languages too.

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Adding the plugin dependency

In your project, create a file for plugin library dependencies project/plugins.sbt and add the following lines:

addSbtPlugin("com.github.gseitz" % "sbt-protobuf" % "0.5.5")

The dependency to "" % "protobuf-java" is automatically added to the Compile scope. The version for protobuf-java can be controlled by the setting version in protobufConfig (set to 3.2.0 by default).

Importing sbt-protobuf settings

To actually "activate" the plugin, its settings need to be included in the build.

import sbtprotobuf.{ProtobufPlugin=>PB}

import sbt._

import sbtprotobuf.{ProtobufPlugin=>PB}

object MyBuild extends Build {
  lazy val myproject = Project(
    id = "myproject",
    base = file(".")
    PB.protobufSettings : _*
    /* custom settings here */

Declaring dependencies

Assuming an artifact contains both *.proto files as well as the binaries of the generated *.java files, you can specify the dependency like so:

libraryDependencies += "some.groupID" % "some.artifactID" % "1.0" % // #1

libraryDependencies += "some.groupID" % "some.artifactID" % "1.0" // #2

Line #1 tells sbt-protobuf that the specified artifact contains *.proto files which it needs to extract and add to the --proto_path for protoc. Internally the setting externalIncludePath is used to track 3rd party proto files.

Line #2 adds the artifact to the regular compile classpath.

The *.proto files of dependencies are extracted and added to the --proto_path parameter for protoc, but are not compiled.

Compiling external proto files

Sometimes it's desirable to compile external proto files (eg. because the library is compiled with an older version of protoc). This can be achieved by adding the following setting:

sourceDirectories in PB.protobufConfig += (externalIncludePath in PB.protobufConfig).value

Packaging proto files

*.proto files can be included in the jar file by adding the following setting to your build definition:

unmanagedResourceDirectories in Compile += (sourceDirectory in PB.protobufConfig).value

Changing the location of the generated java files

By default, the compiled proto files are created in <project-dir>/target/<scala-version>/src_managed/main/compiled_protobuf. Changing the location to <project-dir>/src/generated can be done by adding the following setting to your build definition:

javaSource in PB.protobufConfig := ((sourceDirectory in Compile).value / "generated")

WARNING: The content of this directory is removed by the clean task. Don't set it to a directory containing files you hold dear to your heart.


1,If you occurred compile error,as [...] is already defined as object [...] you could change the compile order as compileOrder := CompileOrder.JavaThenScala,the default is mixed.

2,The inner message's name could not be the .proto's file name.that will cause problem too,you could change the inner message's name or the .proto file name or add the option java_outer_classname = "NewNameNotAsTheFileName"; to you .proto file.

Additional options to protoc

All options passed to protoc are configured via the protobufProtocOptions. To add options, for example to run a custom plugin, add them to this setting key. For example:

protocOptions in PB.protobufConfig ++= Seq("--custom-option")

Additional target directories

The source directories where the files are generated, and the globs used to identify the generated files, are configured by generatedTargets in PB.protobufConfig. In case only Java files are generated, this setting doesn't need to change, since it automatically inherits the value of javaSource in PB.protobufConfig, paired with the glob *.java. In case other types of source files are generated, for example by using a custom plugin (see previous section), the corresponding target directories and source file globs must be configured by adding them to this setting. For example:

generatedTargets in PB.protobufConfig ++= {
  Seq((sourceDirectory in Compile).value / "generated" / "scala", "*.scala")

This plugin uses the generatedTargets setting to:

  • add the generated source directories to cleanFiles and managedSourceDirectories
  • collect the generated files after running protoc and return them to SBT for the compilation phase


All settings and tasks are in the protobuf scope. If you want to execute the protobufGenerate task directly, just run protobuf:protobufGenerate.


namename in shellbuilt-in keydefaultdescription
sourceDirectory sourceDirectory x "src/main/protobuf" Path containing *.proto files.
sourceDirectories sourceDirectories x sourceDirectory This setting is used to collect all directories containing *.proto files to compile
javaSource javaSource x "$sourceManaged/compiled_protobuf" Path for the generated *.java files.
version version x "3.2.0" Which version of the protobuf library should be used. A dependency to "" % "protobuf-java" % "$version" is automatically added to libraryDependencies
protoc protobufProtoc "protoc"The path to the 'protoc' executable.
includePaths protobufIncludePaths Seq($generated-source, protobufExternalIncludePath)The path for additional *.proto files.
externalIncludePath protobufExternalIncludePath target/protobuf_externalThe path to which protobuf:libraryDependencies are extracted and which is used as protobuf:protobufIncludePath for protoc
protocOptions protobufProtocOptions --java_out=[java generated source directory from generatedTargets] the list of options passed to the protoc binary
generatedTargets protobufGeneratedTargets (file(java source directory based on javaSource in PB.protobufConfig), "*.java") the list of target directories and source file globs for the generated files


generateprotobufGeneratePerforms the hardcore compiling action and is automatically executed as a "source generator" in the Compile scope.
unpackDependenciesprotobufUnpackDependenciesExtracts proto files from libraryDependencies into protobufExternalInludePatch
runProtoc protobufRunProtoc A function that executes the protobuf compiler with the given arguments, returning the exit code. The default implementation runs the executable referenced by the `protoc` setting.


sbt-protobuf is based on softprops/coffeescripted-sbt for the sbt-0.10 specific parts and codahale/protobuf-sbt for the protobuf specifics.