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](SECURITY.md).
Homepage: www.grpc.io
Mailing List: grpc-io@googlegroups.com
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Or for Maven with non-Android, add to your `pom.xml`: ```xml io.grpc grpc-netty 1.4.0 io.grpc grpc-protobuf 1.4.0 io.grpc grpc-stub 1.4.0 ``` Or for Gradle with non-Android, add to your dependencies: ```gradle compile 'io.grpc:grpc-netty:1.4.0' compile 'io.grpc:grpc-protobuf:1.4.0' compile 'io.grpc:grpc-stub:1.4.0' ``` For Android client, use `grpc-okhttp` instead of `grpc-netty` and `grpc-protobuf-lite` or `grpc-protobuf-nano` instead of `grpc-protobuf`: ```gradle compile 'io.grpc:grpc-okhttp:1.4.0' compile 'io.grpc:grpc-protobuf-lite:1.4.0' compile 'io.grpc:grpc-stub:1.4.0' ``` [the JARs]: http://search.maven.org/#search%7Cga%7C1%7Cg%3A%22io.grpc%22%20AND%20v%3A%221.4.0%22 Development snapshots are available in [Sonatypes's snapshot repository](https://oss.sonatype.org/content/repositories/snapshots/). 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 1.4.1.Final org.xolstice.maven.plugins protobuf-maven-plugin 0.5.0 com.google.protobuf:protoc:3.3.0:exe:${os.detected.classifier} grpc-java io.grpc:protoc-gen-grpc-java:1.4.0:exe:${os.detected.classifier} compile compile-custom ``` [protobuf-maven-plugin]: https://www.xolstice.org/protobuf-maven-plugin/ For protobuf-based codegen integrated with the Gradle build system, you can use [protobuf-gradle-plugin][]: ```gradle 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:0.8.0' } } protobuf { protoc { artifact = "com.google.protobuf:protoc:3.2.0" } plugins { grpc { artifact = 'io.grpc:protoc-gen-grpc-java:1.4.0' } } generateProtoTasks { all()*.plugins { grpc {} } } } ``` [protobuf-gradle-plugin]: https://github.com/google/protobuf-gradle-plugin How to Build ------------ If you are making changes to gRPC-Java, see the [compiling instructions](COMPILING.md). 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](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 should be trivial to add and are welcome. #### Key Interfaces [Stream Observer](https://github.com/google/grpc-java/blob/master/stub/src/main/java/io/grpc/stub/StreamObserver.java) ### 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 * [Metadata - headers & trailers](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/Metadata.java) * [Status - error code namespace & handling](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/Status.java) #### Client * [Channel - client side binding](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/Channel.java) * [Client Call](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/ClientCall.java) * [Client Interceptor](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/ClientInterceptor.java) #### Server * [Server call handler - analog to Channel on server](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/ServerCallHandler.java) * [Server Call](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/ServerCall.java) ### 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: 1. The [Netty-based](https://github.com/google/grpc-java/blob/master/netty) transport is the main transport implementation based on [Netty](http://netty.io). It is for both the client and the server. 2. The [OkHttp-based](https://github.com/google/grpc-java/blob/master/okhttp) transport is a lightweight transport based on [OkHttp](http://square.github.io/okhttp/). It is mainly for use on Android and is for client only. 3. The [inProcess](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/inprocess) transport is for when a server is in the same process as the client. It is useful for testing. #### Common * [Stream](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/internal/Stream.java) * [Stream Listener](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/internal/StreamListener.java) #### Client * [Client Stream](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/internal/ClientStream.java) * [Client Stream Listener](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/internal/ClientStreamListener.java) #### Server * [Server Stream](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/internal/ServerStream.java) * [Server Stream Listener](https://github.com/google/grpc-java/blob/master/core/src/main/java/io/grpc/internal/ServerStreamListener.java) Examples -------- The [examples](https://github.com/grpc/grpc-java/tree/master/examples) and the [Android example](https://github.com/grpc/grpc-java/tree/master/examples/android) are standalone projects that showcase the usage of gRPC.