gRPC在Java中的实现与应用详解

// 文件：helloworld.proto
syntax = "proto3";
 
package helloworld;
 
// 定义服务
service Greeter {
  // 请求和响应消息
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}
 
// 请求消息
message HelloRequest {
  string name = 1;
}
 
// 响应消息
message HelloReply {
  string message = 1;
}

protoc --proto_path=src --java_out=build/gen src/helloworld.proto

// 文件：GreeterImpl.java
import io.grpc.stub.StreamObserver;
import helloworld.GreeterGrpc;
import helloworld.HelloRequest;
import helloworld.HelloReply;
 
public class GreeterImpl extends GreeterGrpc.GreeterImplBase {
 
    @Override
    public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
        HelloReply reply = HelloReply.newBuilder().setMessage("Hello, " + req.getName()).build();
        responseObserver.onNext(reply);
        responseObserver.onCompleted();
    }
}

// 文件：Server.java
import io.grpc.Server;
import io.grpc.ServerBuilder;
 
public class Server {
    private Server server;
 
    private void start() throws IOException {
        server = ServerBuilder.forPort(8080)
                .addService(new GreeterImpl())
                .build()
                .start();
        System.out.println("Server started, listening on 8080");
        Runtime.getRuntime().addShutdownHook(new Thread() {
            @Override
            public void run() {
                System.err.println("*** shutting down gRPC server since JVM is shutting down");
                Server.this.stop();
                System.err.println("*** server shut down");
            }
        });
    }
 
    private void stop() {
        if (server != null) {
            server.shutdown();
        }
    }
 
    private void blockUntilShutdown() throws InterruptedException {
        if (server != null) {
            server.awaitTermination();
        }
    }
 
    public static void main(String[] args) throws IOException, InterruptedException {
        final Server server = new Server();
        server.start();
        server.blockUntilShutdown();
    }
}

// 文件：Client.java
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import helloworld.GreeterGrpc;
import helloworld.HelloRequest;
import helloworld.HelloReply;
 
public class Client {
    private final ManagedChannel channel;
    private final GreeterGrpc.GreeterBlockingStub blockingStub;
 
    public Client(String host, int port) {
        channel = ManagedChannelBuilder.forAddress(host, port)
                .usePlaintext() // 为了简单，使用明文通信
                .build();
        blockingStub = GreeterGrpc.newBlockingStub(channel);
    }
 
    public void greet(String name) {
        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
        HelloReply response = blockingStub.sayHello(request);
        System.out.println("Greeting: " + response.getMessage());
    }
 
    public void shutdown() throws InterruptedException {
        channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);
    }
 
    public static void main(String[] args) throws InterruptedException {
        Client client = new Client("localhost", 8080);
        client.greet("world");
        client.shutdown();
    }
}

rpc SayHelloStream(stream HelloRequest) returns (stream HelloReply);