gRPC + protobuf + idea + maven + Java Client/Server实践

RPC（Remote Procedure Call）是指远程过程调用，也就是说两台服务器A，B，一个应用部署在A服务器上，想要调用B服务器上应用提供的函数/方法，由于不在一个内存空间，不能直接调用，需要通过网络来表达调用的语义和传达调用的数据。

之前本人介绍过Java简单实现RPC的例子,这里将继续介绍如何快速使用工业级别的RPC技术gRPC。

gRPC是谷歌搞的一个RPC协议，它配套protobuf使用。用户可以通过protobuffer自定义传输数据的格式。

使用过程可以概述为三点：

• 在.proto文件中定义服务。
• 使用协议缓冲区编译器生成服务器和客户端代码。
• 使用Java gRPC API为您的服务编写一个简单的客户端和服务器

1. 新建maven项目，并导入pom文件

   <dependency>
     <groupId>io.grpc</groupId>
     <artifactId>grpc-netty-shaded</artifactId>
     <version>1.23.0</version>
   </dependency>
   <dependency>
     <groupId>io.grpc</groupId>
     <artifactId>grpc-protobuf</artifactId>
     <version>1.23.0</version>
   </dependency>
   <dependency>
     <groupId>io.grpc</groupId>
     <artifactId>grpc-stub</artifactId>
     <version>1.23.0</version>
   </dependency>
   

   <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:3.10.0:exe:${os.detected.classifier}</protocArtifact>
           <pluginId>grpc-java</pluginId>
           <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.23.0:exe:${os.detected.classifier}</pluginArtifact>
         </configuration>
         <executions>
           <execution>
             <goals>
               <goal>compile</goal>
               <goal>compile-custom</goal>
             </goals>
           </execution>
         </executions>
       </plugin>
     </plugins>
   </build>
   

2. 新建proto文件

   syntax = "proto3";
   
   package com.chenqh.proto;
   
   // 生成代码所在包
   option java_package = "com.chenqh.proto";
   // 生成代码类名
   option java_outer_classname = "StudentProto";
   option java_multiple_files = true;
   
   service StudentService{
       rpc GetRealNameByUsername(MyRequest) returns (MyResponse){}
   }
   
   message MyRequest {
       string username = 1;
   }
   message MyResponse {
       string realname = 2;
   }
   

3. 执行命令mvn generate-sources

   

   生成接口如下所示

   

4. 服务端实现接口

   package grpc;
   
   import com.chenqh.proto.MyRequest;
   import com.chenqh.proto.MyResponse;
   import com.chenqh.proto.StudentServiceGrpc;
   import io.grpc.stub.StreamObserver;
   
   public class StudentServiceImpl extends StudentServiceGrpc.StudentServiceImplBase {
       @Override
       public void getRealNameByUsername(MyRequest request, StreamObserver<MyResponse> responseObserver) {
           System.out.println("has received information from client : "+ request.getUsername());
           responseObserver.onNext(MyResponse.newBuilder().setRealname("proto response").build());
           responseObserver.onCompleted();
       }
   }
   

   package grpc;
   
   import io.grpc.ServerBuilder;
   import io.grpc.Server;
   
   import java.io.IOException;
   
   public class GrpcServer {
       private Server server;
   
       private void start() throws IOException {
           /* The port on which the server should run */
           int port = 8899;
           server = ServerBuilder.forPort(port)
                   .addService(new StudentServiceImpl())
                   .build()
                   .start();
           // 回调钩子
           Runtime.getRuntime().addShutdownHook(new Thread() {
               @Override
               public void run() {
                   // Use stderr here since the logger may have been reset by its JVM shutdown hook.
                   System.err.println("*** shutting down gRPC server since JVM is shutting down");
                   GrpcServer.this.stop();
                   System.err.println("*** server shut down");
               }
           });
       }
       private void stop() {
           if (server != null) {
               server.shutdown();
           }
       }
   
       private void awaitTermination() throws InterruptedException {
           if(null != this.server){
               this.server.awaitTermination();
           }
       }
   
       public static void main(String[] args) throws InterruptedException, IOException {
           GrpcServer server = new GrpcServer();
           server.start();
           server.awaitTermination();
       }
   }
   

5. 客户端调用接口

   package grpc;
   
   
   import com.chenqh.proto.MyRequest;
   import com.chenqh.proto.MyResponse;
   import com.chenqh.proto.StudentServiceGrpc;
   import io.grpc.ManagedChannel;
   import io.grpc.ManagedChannelBuilder;
   
   import java.util.concurrent.TimeUnit;
   
   public class Client {
       public static void main(String[] args) throws InterruptedException {
           ManagedChannel managedChannel = ManagedChannelBuilder
                   .forAddress("localhost",8899).usePlaintext(true).build();
           StudentServiceGrpc.StudentServiceBlockingStub blockingStub =
                   StudentServiceGrpc.newBlockingStub(managedChannel);
           //服务端返回单条消息
           MyResponse myResponse = blockingStub.
                   getRealNameByUsername(MyRequest.newBuilder().setUsername("proto  request").build());
           System.out.println(myResponse.getRealname());
           managedChannel.shutdown().awaitTermination(3, TimeUnit.SECONDS);
   
       }
   }
   

6. 启动服务端

   

7. 启动客户端