简介

所谓RPC(remote procedure call 远程过程调用)框架实际是提供了一套机制，使得应用程序之间可以进行通信，而且也遵从server/client模型。使用的时候客户端调用server端提供的接口就像是调用本地的函数一样。

环境配置

创建一个maven项目

引入依赖

  <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-netty-shaded</artifactId>
      <version>1.33.1</version>
  </dependency>
  <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-protobuf</artifactId>
      <version>1.33.1</version>
  </dependency>
  <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-stub</artifactId>
      <version>1.33.1</version>
  </dependency>
  <dependency> <!-- necessary for Java 9+ -->
      <groupId>org.apache.tomcat</groupId>
      <artifactId>annotations-api</artifactId>
      <version>6.0.53</version>
      <scope>provided</scope>
  </dependency>

引入protocol buffer转Java的Maven插件

    <build>
        <extensions>
            <extension>
                <groupId>kr.motd.maven</groupId>
                <artifactId>os-maven-plugin</artifactId>
                <version>1.6.2</version>
            </extension>
        </extensions>
        <plugins>
            <plugin>
                <groupId>org.xolstice.maven.plugins</groupId>
                <artifactId>protobuf-maven-plugin</artifactId>
                <version>0.6.1</version>
                <configuration>
                    <protocArtifact>com.google.protobuf:protoc:3.12.0:exe:${os.detected.classifier}</protocArtifact>
                    <pluginId>grpc-java</pluginId>
                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.33.1:exe:${os.detected.classifier}</pluginArtifact>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>compile-custom</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

项目结构

proto文件编写

syntax = "proto3";

option java_multiple_files = true;
option java_package = "com.unclezs";
option java_outer_classname = "MyGrpcService";
option objc_class_prefix = "HLW";

// The greeting service definition.
service MyGrpcServer {
  // Sends a greeting
  rpc handle (Request) returns (Response) {}
}

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

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

生成代码

服务端代码

package com.unclezs.grpc;

import com.sun.xml.internal.ws.client.sei.ResponseBuilder;
import com.unclezs.MyGrpcServerGrpc;
import com.unclezs.Request;
import com.unclezs.Response;
import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.stub.StreamObserver;

import java.io.IOException;

public class HelloWorldServer {

    private int port = 50051;
    private Server server;

    /**
     * 启动服务
     * @throws IOException
     */
    private void start() throws IOException {
        server = ServerBuilder.forPort(port)
                              .addService(new MyGrpcServerGrpcImpl())
                              .build()
                              .start();

        System.out.println("service start...");

        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 MyGrpcServerGrpcImpl extends MyGrpcServerGrpc.MyGrpcServerImplBase {

        @Override
        public void handle(Request req, StreamObserver<Response> responseObserver) {
            //获取参数
            System.out.println("收到的信息:"+req.getName());

            //这里可以放置具体业务处理代码 start

            //这里可以放置具体业务处理代码 end
            Response response= Response.newBuilder().setMessage("我收到了"+req.getName()).build();
            responseObserver.onNext(response);
            responseObserver.onCompleted();
        }
    }
}

客户端代码

package com.unclezs.grpc;

import com.unclezs.MyGrpcServerGrpc;
import com.unclezs.Request;
import com.unclezs.Response;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.StatusRuntimeException;
import java.util.concurrent.TimeUnit;

public class HelloWorldClient {

    private final ManagedChannel channel; //一个gRPC信道
    private final MyGrpcServerGrpc.MyGrpcServerBlockingStub blockingStub;//阻塞/同步 存根

   //初始化信道和存根
    public HelloWorldClient(String host,int port){
        this(ManagedChannelBuilder.forAddress(host, port)
                                  // Channels are secure by default (via SSL/TLS). For the example we disable TLS to avoid
                                  // needing certificates.
                                  .usePlaintext());
    }

    /** Construct client for accessing RouteGuide server using the existing channel. */
    private HelloWorldClient(ManagedChannelBuilder<?> channelBuilder) {
        channel = channelBuilder.build();
        blockingStub = MyGrpcServerGrpc.newBlockingStub(channel);
    }

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

    //客户端方法
    public  void greet(String name){
        Request request = Request.newBuilder().setName(name).build();
        Response response;
        try {
            response = blockingStub.handle(request);
        } catch (StatusRuntimeException e) {
            System.out.println("RPC调用失败:"+e.getMessage());
            return;
        }
        System.out.println("服务器返回信息:"+response.getMessage());
    }

    public static void main(String[] args) throws InterruptedException {
        HelloWorldClient client = new HelloWorldClient("127.0.0.1",50051);
        try {
            for(int i=0;i<5;i++){
                client.greet("world:"+i);
            }
        }finally {
            client.shutdown();
        }
    }
}

启动后测试

参考

gRPC 官方文档中文版 (opens new window)