java grpc 样例

下面是一个简单的Java gRPC样例：

首先，需要定义一个.proto文件，用于描述gRPC服务和消息格式。例如，创建一个名为HelloWorld.proto的文件，并添加以下内容：

syntax = "proto3";

package com.example.grpc;

option java_multiple_files = true;
option java_package = "com.example.grpc";
option java_outer_classname = "HelloWorldProto";

service HelloWorldService {
  rpc sayHello (HelloRequest) returns (HelloResponse) {}
}

message HelloRequest {
  string name = 1;
}

message HelloResponse {
  string message = 1;
}

使用protoc编译器将.proto文件编译为Java代码。在命令行中运行以下命令：

$ protoc --java_out=. HelloWorld.proto

创建一个Java类，用于实现gRPC服务。例如，创建一个名为HelloWorldServer.java的文件，并添加以下内容：

package com.example.grpc;

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

import java.io.IOException;

public class HelloWorldServer {
    private Server server;

    private void start() throws IOException {
        int port = 50051;
        server = ServerBuilder.forPort(port)
                .addService(new HelloWorldServiceImpl())
                .build()
                .start();

        System.out.println("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 HelloWorldServiceImpl extends HelloWorldServiceGrpc.HelloWorldServiceImplBase {
        @Override
        public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
            String name = request.getName();
            String message = "Hello " + name + "!";
            HelloResponse response = HelloResponse.newBuilder().setMessage(message).build();
            responseObserver.onNext(response);
            responseObserver.onCompleted();
        }
    }
}

创建一个Java类，用于实现gRPC客户端。例如，创建一个名为HelloWorldClient.java的文件，并添加以下内容：

package com.example.grpc;

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

public class HelloWorldClient {
    private final ManagedChannel channel;
    private final HelloWorldServiceGrpc.HelloWorldServiceBlockingStub blockingStub;

    public HelloWorldClient(String host, int port) {
        channel = ManagedChannelBuilder.forAddress(host, port)
                .usePlaintext()
                .build();
        blockingStub = HelloWorldServiceGrpc.newBlockingStub(channel);
    }

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

    public void sayHello(String name) {
        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
        HelloResponse response = blockingStub.sayHello(request);
        System.out.println("Response: " + response.getMessage());
    }

    public static void main(String[] args) throws InterruptedException {
        HelloWorldClient client = new HelloWorldClient("localhost", 50051);
        client.sayHello("John Doe");
        client.shutdown();
    }
}

运行gRPC服务器和客户端代码。在命令行中分别运行以下命令：

$ java com.example.grpc.HelloWorldServer
$ java com.example.grpc.HelloWorldClient

这个样例演示了一个简单的gRPC服务和客户端的交互。服务器接收一个名字作为输入，并返回一个问候消息。客户端发送一个名字给服务器，并打印出服务器返回的问候消息