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grpc
8.1K Stars 2.8K Forks Apache License 2.0 4.6K Commits 492 Opened issues

Description

The Java gRPC implementation. HTTP/2 based RPC

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gRPC-Java - An RPC library and framework

gRPC-Java works with JDK 7. gRPC-Java clients are supported on Android API levels 16 and up (Jelly Bean and later). Deploying gRPC servers on an Android device is not supported.

TLS usage typically requires using Java 8, or Play Services Dynamic Security Provider on Android. Please see the Security Readme.

Homepage: grpc.io
Mailing List: [email protected]

Join the chat at https://gitter.im/grpc/grpc Build Status Coverage Status

Getting Started

For a guided tour, take a look at the quick start guide or the more explanatory gRPC basics.

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

Download

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

pom.xml
:
xml

  io.grpc
  grpc-netty-shaded
  1.34.0


  io.grpc
  grpc-protobuf
  1.34.0


  io.grpc
  grpc-stub
  1.34.0

 
  org.apache.tomcat
  annotations-api
  6.0.53
  provided

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

gradle
implementation 'io.grpc:grpc-netty-shaded:1.34.0'
implementation 'io.grpc:grpc-protobuf:1.34.0'
implementation 'io.grpc:grpc-stub:1.34.0'
compileOnly 'org.apache.tomcat:annotations-api:6.0.53' // necessary for Java 9+

For Android client, use

grpc-okhttp
instead of
grpc-netty-shaded
and
grpc-protobuf-lite
instead of
grpc-protobuf
:
gradle
implementation 'io.grpc:grpc-okhttp:1.34.0'
implementation 'io.grpc:grpc-protobuf-lite:1.34.0'
implementation 'io.grpc:grpc-stub:1.34.0'
compileOnly 'org.apache.tomcat:annotations-api:6.0.53' // necessary for Java 9+

Development snapshots are available in Sonatypes's snapshot repository.

Generated Code

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):
xml

  
    
      kr.motd.maven
      os-maven-plugin
      1.6.2
    
  
  
    
      org.xolstice.maven.plugins
      protobuf-maven-plugin
      0.6.1
      
        com.google.protobuf:protoc:3.12.0:exe:${os.detected.classifier}
        grpc-java
        io.grpc:protoc-gen-grpc-java:1.34.0:exe:${os.detected.classifier}
      
      
        
          
            compile
            compile-custom
          
        
      
    
  

For protobuf-based codegen integrated with the Gradle build system, you can use protobuf-gradle-plugin: ```gradle plugins { id 'com.google.protobuf' version '0.8.14' }

protobuf { protoc { artifact = "com.google.protobuf:protoc:3.12.0" } plugins { grpc { artifact = 'io.grpc:protoc-gen-grpc-java:1.34.0' } } generateProtoTasks { all()*.plugins { grpc {} } } } ```

The prebuilt protoc-gen-grpc-java binary uses glibc on Linux. If you are compiling on Alpine Linux, you may want to use the Alpine grpc-java package which uses musl instead.

API Stability

APIs annotated with

@Internal
are for internal use by the gRPC library and should not be used by gRPC users. APIs annotated with
@ExperimentalApi
are subject to change in future releases, and library code that other projects may depend on should not use these APIs.

We recommend using the grpc-java-api-checker (an Error Prone plugin) to check for usages of

@ExperimentalApi
and
@Internal
in any library code that depends on gRPC. It may also be used to check for
@Internal
usage or unintended
@ExperimentalApi
consumption in non-library code.

How to Build

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

High-level Components

At a high level there are three distinct layers to the library: Stub, Channel, and 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 are easy and encouraged.

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.

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. 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:

  1. The Netty-based transport is the main transport implementation based on Netty. It is for both the client and the server.
  2. The OkHttp-based transport is a lightweight transport based on OkHttp. It is mainly for use on Android and is for client only.
  3. The in-process transport is for when a server is in the same process as the client. It is useful for testing, while also being safe for production use.

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