commit	cb2f62bbbf5c5a190a686e2be61e78df363b8b6e	[log] [tgz]
author	Eric Anderson <ejona@google.com>	Wed Mar 07 09:30:15 2018 -0800
committer	Eric Anderson <ejona@google.com>	Wed Mar 07 13:39:47 2018 -0800
tree	b9463e1e7a24f4c57f0e294af24e4cc29a783563
parent	ca7b3dad119438e66a3945d6f447eb4b80ba12f4 [diff]

tree: b9463e1e7a24f4c57f0e294af24e4cc29a783563

README.md

gRPC-Java - An RPC library and framework

gRPC-Java works with JDK 6. On Android, gRPC-Java supports Android API levels 14 and up (Ice Cream Sandwich and later).

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>1.10.0</version>
</dependency>
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-protobuf</artifactId>
  <version>1.10.0</version>
</dependency>
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-stub</artifactId>
  <version>1.10.0</version>
</dependency>

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

compile 'io.grpc:grpc-netty:1.10.0'
compile 'io.grpc:grpc-protobuf:1.10.0'
compile 'io.grpc:grpc-stub:1.10.0'

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

compile 'io.grpc:grpc-okhttp:1.10.0'
compile 'io.grpc:grpc-protobuf-lite:1.10.0'
compile 'io.grpc:grpc-stub:1.10.0'

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 (Eclipse and NetBeans users should also look at os-maven-plugin's IDE documentation):

<build>
  <extensions>
    <extension>
      <groupId>kr.motd.maven</groupId>
      <artifactId>os-maven-plugin</artifactId>
      <version>1.5.0.Final</version>
    </extension>
  </extensions>
  <plugins>
    <plugin>
      <groupId>org.xolstice.maven.plugins</groupId>
      <artifactId>protobuf-maven-plugin</artifactId>
      <version>0.5.0</version>
      <configuration>
        <protocArtifact>com.google.protobuf:protoc:3.5.1-1:exe:${os.detected.classifier}</protocArtifact>
        <pluginId>grpc-java</pluginId>
        <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.10.0:exe:${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:0.8.3'
  }
}

protobuf {
  protoc {
    artifact = "com.google.protobuf:protoc:3.5.1-1"
  }
  plugins {
    grpc {
      artifact = 'io.grpc:protoc-gen-grpc-java:1.10.0'
    }
  }
  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

The examples and the Android example are standalone projects that showcase the usage of gRPC.