Java 开发 gRPC 服务和客户端

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Java 开发 gRPC 服务和客户端
新建一个普通的Maven项目：

配置pom文件，导入gRPC的依赖和插件

pom 中增加外部依赖

<dependency>
    <groupId>io.grpc</groupId>
    <artifactId>grpc-all</artifactId>
    <version>0.13.2</version>
</dependency>

注意，下面的增加 maven 插件： protobuf-maven-plugin: protobuf 的插件，不是 gRPC的插件，产生的代码只会是 protobuf 序列化、反序列化的代码，没有gRPC通讯部分的代码。

增加 maven 插件： protobuf-maven-plugin: 配置
```
<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>
        
        <protocArtifact>com.google.protobuf:protoc:3.0.0-beta-2:exe:${os.detected.classifier}</protocArtifact>
        <pluginId>grpc-java</pluginId>
        <pluginArtifact>io.grpc:protoc-gen-grpc-java:0.13.2:exe:${os.detected.classifier}</pluginArtifact>
      </configuration>
      <executions>
        <execution>
          <goals>
            <goal>compile</goal>
            <goal>compile-custom</goal>
          </goals>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>
```
```
完整的 pom 文件如下：
```
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ghj1976</groupId>
    <artifactId>myGRPCDemo2</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-all</artifactId>
            <version>0.13.2</version>
        </dependency>
    </dependencies>
    <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>
                    
                    <protocArtifact>com.google.protobuf:protoc:3.0.0-beta-2:exe:${os.detected.classifier}</protocArtifact>
                    <pluginId>grpc-java</pluginId>
                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:0.13.2:exe:${os.detected.classifier}</pluginArtifact>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>compile-custom</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

编写 proto 文件，并编译产生对应的 java文件

简单期间这里直接用的 helloworld.proto 文件，内容如下：

// Copyright 2015, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

syntax = "proto3";

option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldProto";
option objc_class_prefix = "HLW";

package helloworld;

// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
string name = 1;
}

// The response message containing the greetings
message HelloReply {
string message = 1;
}

生成 protobuf 序列化和反序列化代码

注意，这里我们使用的maven 插件是 protobuf的插件，只能产生protobuf的序列化和反序列化的代码，不能产生gRPC通讯的代码。

如果我们只需要产生这部分代码是，才需要使用这个插件。

这个插件的用法参考下图：

如果用命令行生成，则命令是：

$ protoc --java_out=./java/ ./proto/helloworld.proto

生成 gRPC 通讯部分代码

这时候我们应该使用的是 protoc-gen-grpc-java插件。

这个插件的获取和编译方法请参考： http://www.cnblogs.com/ghj1976/p/5454881.html

我们这时候产生对应java代码的命令如下：

$ protoc --plugin=protoc-gen-grpc-java=/Users/ghj1976/project/github/grpc/grpc-java/compiler/build/exe/java_plugin/protoc-gen-grpc-java --grpc-java_out=./java/ ./proto/helloworld.proto

这两部生成的文件如下：

GreeterGrpc.java 是 protoc-gen-grpc-java 插件生成的，其他文件时 protoc 生成的。

编写服务器端代码

我们服务器端的代码如下，生成的文件在io.grpc.examples.helloworld，我们的服务器端代码在 com.ghj1976 ：

package com.ghj1976;

import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.examples.helloworld.GreeterGrpc;
import io.grpc.examples.helloworld.HelloReply;
import io.grpc.examples.helloworld.HelloRequest;
import io.grpc.stub.StreamObserver;

import java.io.IOException;
import java.util.logging.Logger;

/**
* Created by ghj1976 on 16/5/4.
*/
public class HelloWorldServer {

    private static final Logger logger = Logger.getLogger(HelloWorldServer.class.getName());

    private int port = 50051;
    private Server server;

    private void start() throws IOException{
        server = ServerBuilder.forPort(port)
                .addService(new GreeterImpl())
                .build()
                .start();
        logger.info("Server started, listening on "+ port);

        Runtime.getRuntime().addShutdownHook(new Thread(){

            @Override
            public void run(){

                System.err.println("*** shutting down gRPC server since JVM is shutting down");
                HelloWorldServer.this.stop();
                System.err.println("*** server shut down");
            }
        });
    }

    private void stop(){
        if (server != null){
            server.shutdown();
        }
    }

    // block 一直到退出程序
    private void blockUntilShutdown() throws InterruptedException {
        if (server != null){
            server.awaitTermination();
        }
    }

    public static void main(String[] args) throws IOException, InterruptedException {

        final HelloWorldServer server = new HelloWorldServer();
        server.start();
        server.blockUntilShutdown();
    }

    // 实现定义一个实现服务接口的类
    private class GreeterImpl extends GreeterGrpc.AbstractGreeter {

        @Override
        public void sayHello(HelloRequest req,StreamObserver<HelloReply> responseObserver){
            HelloReply reply = HelloReply.newBuilder().setMessage(("Hello "+req.getName())).build();
            responseObserver.onNext(reply);
            responseObserver.onCompleted();
        }
    }
}

运行这个类的 main 方法，就可以在 50051 端口启动服务。

go实现的服务器端代码在:

https://github.com/grpc/grpc-go/blob/master/examples/helloworld/greeter_server/main.go

编写客户端代码

为了实现跨语言的调用，我们可以用下面 go 实现的客户端来试验。

https://github.com/grpc/grpc-go/blob/master/examples/helloworld/greeter_client/main.go

如果用 Java 写客户端的话，则是下面代码：

package com.ghj1976;

import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.StatusRuntimeException;
import io.grpc.examples.helloworld.GreeterGrpc;
import io.grpc.examples.helloworld.HelloReply;
import io.grpc.examples.helloworld.HelloRequest;

import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Created by ghj1976 on 16/5/4.
*/
public class HelloWorldClient {

    private final ManagedChannel channel;
    private final GreeterGrpc.GreeterBlockingStub blockingStub;
    private static final Logger logger = Logger.getLogger(HelloWorldClient.class.getName());

    public HelloWorldClient(String host,int port){
        channel = ManagedChannelBuilder.forAddress(host,port)
                .usePlaintext(true)
                .build();

        blockingStub = GreeterGrpc.newBlockingStub(channel);
    }

    public void shutdown() throws InterruptedException {
        channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);
    }

    public void greet(String name){
        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
        HelloReply response;
        try{
            response = blockingStub.sayHello(request);
        } catch (StatusRuntimeException e)
        {
            logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
            return;
        }
        logger.info("Greeting: "+response.getMessage());
    }

    public static void main(String[] args) throws InterruptedException {
        HelloWorldClient client = new HelloWorldClient("127.0.0.1",50051);
        try{
            String user = "world";
            if (args.length > 0){
                user = args[0];
            }
            client.greet(user);
        }finally {
            client.shutdown();
        }
    }
}
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原文地址：https://www.cnblogs.com/ghj1976/p/5458176.html

Java 开发 gRPC 服务和客户端

新建一个普通的Maven项目：

配置pom文件，导入gRPC的依赖和插件

编写 proto 文件，并编译产生对应的 java文件

编写服务器端代码

编写客户端代码