Java中使用GRPC

0.编写.proto文件：

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;

service Greeter {
    rpc SayHello (HelloRequest) returns (HelloReply) {}
}

message HelloRequest {
    string name = 1;
}

message HelloReply {
    string message = 1;
}

1.编译.proto生成对应Java源文件：

protoc --grpc_out=..\java --plugin=protoc-gen-grpc=D:\Dev\protoc\protoc-gen-grpc-java-1.9.1-windows-x86_64.exe helloworld.proto

2.编写Server端代码：

package io.grpc.examples.helloworld;

import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.stub.StreamObserver;

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

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

    private Server server;

    private void start() throws IOException {
        int port = 50051;
        server = NettyServerBuilder.forPort(port)
                .addService(new GreeterImpl())
                .build()
                .start();
        logger.info("Server started, listening on " + port);
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
            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();
        }
    }

    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();
    }

    static class GreeterImpl extends GreeterGrpc.GreeterImplBase {

        @Override
        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
            String name = req.getName();
            logger.log(Level.INFO, "Received name: " + name);
            HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + name).build();
            responseObserver.onNext(reply);
            responseObserver.onCompleted();
        }
    }
}

3.编写Client端代码：

package io.grpc.examples.helloworld;

import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.StatusRuntimeException;

import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;

public class HelloWorldClient {
    private static final Logger logger = Logger.getLogger(HelloWorldClient.class.getName());

    private final ManagedChannel channel;
    private final GreeterGrpc.GreeterBlockingStub blockingStub;

    private HelloWorldClient(String host, int port) {
        this(ManagedChannelBuilder.forAddress(host, port)
                // needing certificates.
                .usePlaintext()
                .build());
    }

    private HelloWorldClient(ManagedChannel channel) {
        this.channel = channel;
        blockingStub = GreeterGrpc.newBlockingStub(channel);
    }

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

    private void greet(String name) {
        logger.info("Will try to greet " + 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 Exception {
        HelloWorldClient client = new HelloWorldClient("localhost", 50051);
        try {
            for(int i=0; i<10; i++){
                String user = "World!";
                if (args.length > 0) {
                    user = args[0]; /* Use the arg as the name to greet if provided */
                }
                client.greet(user);
                Thread.sleep(3000);
            }
        } finally {
            client.shutdown();
        }
    }
}

4.分别运行Server、Client代码，运行截图如下：

 注：官方代码Server端的ServerBuilder已过时，如用较新的GRPC库，需改成NettyServerBuilder。