maven集成Protobuff并创建GRpc示例

1. 创建protobuff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;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

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

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

具体写法可以搜索：protobuff

2. 添加gRPC-java的依赖：

<dependency>
    <groupId>io.grpc</groupId>
    <artifactId>grpc-all</artifactId>
    <version>${grpc-version}</version>
</dependency>

我的grpc-version为1.8.0

可以在maven查看grpc-all的各个版本，每个版本对应的protobuff-java版本不一样，1.8.0对应的是3.4.0，但我后面的插件对应的版本是3.3.1，所以会下两个版本。看其他帖子说必须得保证两个版本一致，但我的不一致也可以。

3. 添加protocol buffers编译插件:

可以搜maven protoc查看相关资料

<build>
    <extensions>
        <extension>
            <groupId>kr.motd.maven</groupId>
            <artifactId>os-maven-plugin</artifactId>
            <version>1.4.1.Final</version>
        </extension>
    </extensions>
    <plugins>
        <plugin>
            <groupId>org.xolstice.maven.plugins</groupId>
            <artifactId>protobuf-maven-plugin</artifactId>
            <version>0.5.0</version>
            <configuration>
                <!--
                    The version of protoc must match protobuf-java. If you don't depend on
                    protobuf-java directly, you will be transitively depending on the
                    protobuf-java version that grpc depends on.
                -->
                <protocArtifact>com.google.protobuf:protoc:3.5.0:exe:${os.detected.classifier}</protocArtifact>
                <pluginId>grpc-java</pluginId>
                <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc-version}:exe:${os.detected.classifier}</pluginArtifact>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                        <goal>compile-custom</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

其中os-maven-plugin用于识别你的操作系统的版本，提供${os.detected.classifier}参数供后面使用，没有其他的作用。我使用了1.5.0-Final，结果得不到${os.detected.classifier}属性，所以换了低版本的1.4.1.Final
grpc-version和你grpc-all依赖的版本一致，我的是1.8.0
该插件用于配置protoc，会生成相应的插件：
4. 运行第一个插件（compile）：
生成一堆java文件和一个.exe文件，可以看到生成的protoc后面有一串3.5.0，这个是在写protobuf-maven-plugin插件的时候在<configuration></configuration>中配置的。后缀windows-x86_64的系统版本标识，是由os-maven-plugin插件获得的。
5. 运行第二个插件（compile-custom）：
他会生成一个exe文件和一个java文件
6. 编写服务端代码：

package com.zj.layoutserver.server;
import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.examples.helloworld.GreeterGrpc;
import io.grpc.examples.helloworld.HelloReply;
import io.grpc.examples.helloworld.HelloRequest;
import io.grpc.stub.StreamObserver;

import java.io.IOException;

public class HelloWorldServer {


    private int port = 50051;
    private Server server;

    private void start() throws IOException {
        server = ServerBuilder.forPort(port)
                .addService(new GreeterImpl())
                .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 GreeterImpl extends GreeterGrpc.GreeterImplBase {


        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
            System.out.println("service:"+req.getName());
            HelloReply reply = HelloReply.newBuilder().setMessage(("Hello: " + req.getName())).build();
            responseObserver.onNext(reply);
            responseObserver.onCompleted();
        }
    }
}

7. 编写客户端代码：

package com.zj.layoutserver.client;

import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.examples.helloworld.GreeterGrpc;
import io.grpc.examples.helloworld.HelloReply;
import io.grpc.examples.helloworld.HelloRequest;

import java.util.concurrent.TimeUnit;

public class HelloWorldClient {

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


    public HelloWorldClient(String host,int port){
        channel = ManagedChannelBuilder.forAddress(host,port)
                .usePlaintext(true)
                .build();

        blockingStub = GreeterGrpc.newBlockingStub(channel);
    }


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

    public  void greet(String name){
        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
        HelloReply response = blockingStub.sayHello(request);
        System.out.println(response.getMessage());

    }

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

    }
}

然后依次运行服务端和客户端就可以了。

有很多原理可以参考网上的其他教程

maven集成Protobuff并创建GRpc示例

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