commit	dc027ff34670e4e330bcdc04bfda93818b36399a	[log] [tgz]
author	Carl Mastrangelo <notcarl@google.com>	Mon Jun 27 15:46:04 2016 -0700
committer	Carl Mastrangelo <notcarl@google.com>	Tue Jun 28 16:10:38 2016 -0700
tree	3c008751f360e12c69e3b98ebaea8c36f65e5495
parent	4b17a2e31722b089193908c6233ea89c18e33a44 [diff]

tree: 3c008751f360e12c69e3b98ebaea8c36f65e5495

README.md

gRPC-Java - An RPC library and framework

gRPC-Java works with JDK 6. TLS usage typically requires using Java 8, or Play Services Dynamic Security Provider on Android. Please see the Security Readme.

Download

Download the JARs. Or for Maven with non-Android, add to your pom.xml:

<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-netty</artifactId>
  <version>0.14.0</version>
</dependency>
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-protobuf</artifactId>
  <version>0.14.0</version>
</dependency>
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-stub</artifactId>
  <version>0.14.0</version>
</dependency>

Or for Gradle with non-Android, add to your dependencies:

compile 'io.grpc:grpc-netty:0.14.0'
compile 'io.grpc:grpc-protobuf:0.14.0'
compile 'io.grpc:grpc-stub:0.14.0'

For Android client, use grpc-okhttp instead of grpc-netty and grpc-protobuf-nano or grpc-protobuf-lite instead of grpc-protobuf:

compile 'io.grpc:grpc-okhttp:0.14.0'
compile 'io.grpc:grpc-protobuf-nano:0.14.0'
compile 'io.grpc:grpc-stub:0.14.0'

Development snapshots are available in Sonatypes's snapshot repository.

For protobuf-based codegen, you can put your proto files in the src/main/proto and src/test/proto directories along with an appropriate plugin.

For protobuf-based codegen integrated with the Maven build system, you can use protobuf-maven-plugin:

<build>
  <extensions>
    <extension>
      <groupId>kr.motd.maven</groupId>
      <artifactId>os-maven-plugin</artifactId>
      <version>1.4.1.Final</version>
    </extension>
  </extensions>
  <plugins>
    <plugin>
      <groupId>org.xolstice.maven.plugins</groupId>
      <artifactId>protobuf-maven-plugin</artifactId>
      <version>0.5.0</version>
      <configuration>
        <!--
          The version of protoc must match protobuf-java. If you don't depend on
          protobuf-java directly, you will be transitively depending on the
          protobuf-java version that grpc depends on.
        -->
        <protocArtifact>com.google.protobuf:protoc:3.0.0-beta-2:exe:${os.detected.classifier}</protocArtifact>
        <pluginId>grpc-java</pluginId>
        <pluginArtifact>io.grpc:protoc-gen-grpc-java:0.14.0:exe:${os.detected.classifier}</pluginArtifact>
      </configuration>
      <executions>
        <execution>
          <goals>
            <goal>compile</goal>
            <goal>compile-custom</goal>
          </goals>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

For protobuf-based codegen integrated with the Gradle build system, you can use protobuf-gradle-plugin:

apply plugin: 'java'
apply plugin: 'com.google.protobuf'

buildscript {
  repositories {
    mavenCentral()
  }
  dependencies {
    // ASSUMES GRADLE 2.12 OR HIGHER. Use plugin version 0.7.5 with earlier
    // gradle versions
    classpath 'com.google.protobuf:protobuf-gradle-plugin:0.7.7'
  }
}

protobuf {
  protoc {
    // The version of protoc must match protobuf-java. If you don't depend on
    // protobuf-java directly, you will be transitively depending on the
    // protobuf-java version that grpc depends on.
    artifact = "com.google.protobuf:protoc:3.0.0-beta-2"
  }
  plugins {
    grpc {
      artifact = 'io.grpc:protoc-gen-grpc-java:0.14.0'
    }
  }
  generateProtoTasks {
    all()*.plugins {
      grpc {}
    }
  }
}

How to Build

If you are making changes to gRPC-Java, see the compiling instructions.

Navigating Around the Source

Here's a quick readers' guide to the code to help folks get started. At a high level there are three distinct layers to the library: Stub, Channel & Transport.

Stub

The Stub layer is what is exposed to most developers and provides type-safe bindings to whatever datamodel/IDL/interface you are adapting. gRPC comes with a plugin to the protocol-buffers compiler that generates Stub interfaces out of .proto files, but bindings to other datamodel/IDL should be trivial to add and are welcome.

Key Interfaces

Stream Observer

Channel

The Channel layer is an abstraction over Transport handling that is suitable for interception/decoration and exposes more behavior to the application than the Stub layer. It is intended to be easy for application frameworks to use this layer to address cross-cutting concerns such as logging, monitoring, auth etc. Flow-control is also exposed at this layer to allow more sophisticated applications to interact with it directly.

Common

Client

Server

Transport

The Transport layer does the heavy lifting of putting and taking bytes off the wire. The interfaces to it are abstract just enough to allow plugging in of different implementations. Transports are modeled as Stream factories. The variation in interface between a server Stream and a client Stream exists to codify their differing semantics for cancellation and error reporting.

Note the transport layer API is considered internal to gRPC and has weaker API guarantees than the core API under package io.grpc.

gRPC comes with three Transport implementations:

The Netty-based transport is the main transport implementation based on Netty. It is for both the client and the server.
The OkHttp-based transport is a lightweight transport based on OkHttp. It is mainly for use on Android and is for client only.
The inProcess transport is for when a server is in the same process as the client. It is useful for testing.

Common

Client

Server

Examples

Tests showing how these layers are composed to execute calls using protobuf messages can be found here https://github.com/google/grpc-java/tree/master/interop-testing/src/main/java/io/grpc/testing/integration