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https://github.com/grpc/grpc-java

The Java gRPC implementation. HTTP/2 based RPC
https://github.com/grpc/grpc-java

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The Java gRPC implementation. HTTP/2 based RPC

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README 

        
gRPC-Java - An RPC library and framework

========================================



  

    Homepage:

    grpc.io

  

  

    Mailing List:

    [email protected]

  



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Supported Platforms

-------------------



gRPC-Java supports Java 8 and later. Android minSdkVersion 21 (Lollipop) and

later are supported with [Java 8 language desugaring][android-java-8].



TLS usage on Android typically requires Play Services Dynamic Security Provider.

Please see the [Security Readme](SECURITY.md).



Older Java versions are not directly supported, but a branch remains available

for fixes and releases. See [gRFC P5 JDK Version Support

Policy][P5-jdk-version-support].



Java version | gRPC Branch

------------ | -----------

7            | 1.41.x



[android-java-8]: https://developer.android.com/studio/write/java8-support#supported_features

[P5-jdk-version-support]: https://github.com/grpc/proposal/blob/master/P5-jdk-version-support.md#proposal



Getting Started

---------------



For a guided tour, take a look at the [quick start

guide](https://grpc.io/docs/languages/java/quickstart) or the more explanatory [gRPC

basics](https://grpc.io/docs/languages/java/basics).



The [examples](https://github.com/grpc/grpc-java/tree/v1.68.1/examples) and the

[Android example](https://github.com/grpc/grpc-java/tree/v1.68.1/examples/android)

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

  1.68.1

  runtime



  io.grpc

  grpc-protobuf

  1.68.1



  io.grpc

  grpc-stub

  1.68.1



 

  org.apache.tomcat

  annotations-api

  6.0.53

  provided



```



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

```gradle

runtimeOnly 'io.grpc:grpc-netty-shaded:1.68.1'

implementation 'io.grpc:grpc-protobuf:1.68.1'

implementation 'io.grpc:grpc-stub:1.68.1'

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:1.68.1'

implementation 'io.grpc:grpc-protobuf-lite:1.68.1'

implementation 'io.grpc:grpc-stub:1.68.1'

compileOnly 'org.apache.tomcat:annotations-api:6.0.53' // necessary for Java 9+

```



For [Bazel](https://bazel.build), you can either

[use Maven](https://github.com/bazelbuild/rules_jvm_external)

(with the GAVs from above), or use `@io_grpc_grpc_java//api` et al (see below).



[the JARs]:

https://search.maven.org/search?q=g:io.grpc%20AND%20v:1.68.1



Development snapshots are available in [Sonatypes's snapshot

repository](https://oss.sonatype.org/content/repositories/snapshots/).



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](https://github.com/trustin/os-maven-plugin#issues-with-eclipse-m2e-or-other-ides)):

```xml



  

    

      kr.motd.maven

      os-maven-plugin

      1.7.1

    

  

  

    

      org.xolstice.maven.plugins

      protobuf-maven-plugin

      0.6.1

      

        com.google.protobuf:protoc:3.25.5:exe:${os.detected.classifier}

        grpc-java

        io.grpc:protoc-gen-grpc-java:1.68.1:exe:${os.detected.classifier}

      

      

        

          

            compile

            compile-custom

          

        

      

    

  



```



[protobuf-maven-plugin]: https://www.xolstice.org/protobuf-maven-plugin/



For non-Android protobuf-based codegen integrated with the Gradle build system,

you can use [protobuf-gradle-plugin][]:

```gradle

plugins {

    id 'com.google.protobuf' version '0.9.4'

}



protobuf {

  protoc {

    artifact = "com.google.protobuf:protoc:3.25.5"

  }

  plugins {

    grpc {

      artifact = 'io.grpc:protoc-gen-grpc-java:1.68.1'

    }

  }

  generateProtoTasks {

    all()*.plugins {

      grpc {}

    }

  }

}

```



[protobuf-gradle-plugin]: https://github.com/google/protobuf-gradle-plugin



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.



[Alpine grpc-java package]: https://pkgs.alpinelinux.org/package/edge/community/x86_64/grpc-java



For Android protobuf-based codegen integrated with the Gradle build system, also

use protobuf-gradle-plugin but specify the 'lite' options:



```gradle

plugins {

    id 'com.google.protobuf' version '0.9.4'

}



protobuf {

  protoc {

    artifact = "com.google.protobuf:protoc:3.25.5"

  }

  plugins {

    grpc {

      artifact = 'io.grpc:protoc-gen-grpc-java:1.68.1'

    }

  }

  generateProtoTasks {

    all().each { task ->

      task.builtins {

        java { option 'lite' }

      }

      task.plugins {

        grpc { option 'lite' }

      }

    }

  }

}



```



For [Bazel](https://bazel.build), use the [`proto_library`](https://github.com/bazelbuild/rules_proto)

and the [`java_proto_library`](https://bazel.build/reference/be/java#java_proto_library) (no `load()` required) 

and `load("@io_grpc_grpc_java//:java_grpc_library.bzl", "java_grpc_library")` (from this project), as in

[this example `BUILD.bazel`](https://github.com/grpc/grpc-java/blob/master/examples/BUILD.bazel).



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](https://github.com/grpc/grpc-java-api-checker)

(an [Error Prone](https://github.com/google/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](COMPILING.md).



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](https://github.com/google/grpc-java/blob/master/compiler) 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 multiple Transport implementations:



1. The Netty-based HTTP/2 transport is the main transport implementation based

   on [Netty](https://netty.io). It is not officially supported on Android.

   There is a "grpc-netty-shaded" version of this transport. It is generally

   preferred over using the Netty-based transport directly as it requires less

   dependency management and is easier to upgrade within many applications.

2. The OkHttp-based HTTP/2 transport is a lightweight transport based on

   [Okio](https://square.github.io/okio/) and forked low-level parts of

   [OkHttp](https://square.github.io/okhttp/). It is mainly for use on Android.

3. The in-process transport is for when a server is in the same process as the

   client. It is used frequently for testing, while also being safe for

   production use.

4. The Binder transport is for Android cross-process communication on a single

   device.