java使用gRPC框架

官方文档

https://grpc.io/docs/languages/java/quickstart/

官方example

https://github.com/grpc/grpc-java

1.定义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;

// 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;
}

proto定义，参考官方文档

https://github.com/grpc/grpc-java/blob/master/examples/src/main/proto/helloworld.proto

2.编译proto文件

1.使用protoc命令编译

在项目目录下运行编译命令，里面使用了protoc-gen-grpc-java执行文件，需要参考：编译grpc-java项目生成protoc-gen-grpc-java文件

protoc --plugin=protoc-gen-grpc-java=./protoc-gen-grpc-java -I=./ --java_out=./src/main/java/ --grpc-java_out=./src/main/java/ ./src/main/proto/helloworld.proto

得到proto文件中定义的model和service的java代码

2.使用maven插件编译

当然也可以使用maven插件来生成proto model和service的java代码，需要在pom.xml中添加插件，如下

    <build>
        <extensions>
            <extension>
                <groupId>kr.motd.maven</groupId>
                <artifactId>os-maven-plugin</artifactId>
                <version>1.5.0.Final</version>
            </extension>
        </extensions>
        <plugins>
            <plugin>
                <groupId>org.xolstice.maven.plugins</groupId>
                <artifactId>protobuf-maven-plugin</artifactId>
                <version>0.5.1</version>
                <configuration>
                    <protocArtifact>com.google.protobuf:protoc:3.5.1-1:exe:${os.detected.classifier}</protocArtifact>
                    <pluginId>grpc-java</pluginId>
                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.14.0:exe:${os.detected.classifier}</pluginArtifact>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>compile-custom</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>

        </plugins>
    </build>

然后点击protobuf:compile和protobuf:comile-custome即可，参考：idea中.proto文件生成model类和service类

target目录下就会生成java代码

3.编写server和client

1.添加依赖

        <!-- log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <!--google-->
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>31.1-jre</version>
        </dependency>
        <!--grpc-->
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-netty-shaded</artifactId>
            <version>1.59.0</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-protobuf</artifactId>
            <version>1.59.0</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-stub</artifactId>
            <version>1.59.0</version>
        </dependency>

2.server代码

官方例子

https://github.com/grpc/grpc-java/blob/master/examples/src/main/java/io/grpc/examples/helloworld/HelloWorldServer.java

package com.interview.rpc;

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 org.apache.log4j.Logger;

import java.io.IOException;

public class HelloWorldServer {

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

    private int port = 50051;
    private Server server;

    public static void main(String[] args) throws IOException, InterruptedException {
        final HelloWorldServer server = new HelloWorldServer();
        server.start();
        server.blockUntilShutdown();
    }

    private void start() throws IOException {
        server = ServerBuilder.forPort(port)
                .addService(new GreeterImpl())
                .build()
                .start();
        logger.info("Server started, listening on " + port);

        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();
        }
    }

    // 实现 定义一个实现服务接口的类
    private 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();
            System.out.println("Message from gRPC-Client:" + req.getName());
            System.out.println("Message Response:" + reply.getMessage());
        }
    }

}

3.client代码

官方例子

https://github.com/grpc/grpc-java/blob/master/examples/src/main/java/io/grpc/examples/helloworld/HelloWorldClient.java

代码

package com.interview.rpc;

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

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

public class HelloWorldClient {

    private final ManagedChannel channel;
    private final GreeterGrpc.GreeterBlockingStub blockingStub;
    private static final Logger logger = Logger.getLogger(HelloWorldClient.class.getName());

    public static void main(String[] args) throws InterruptedException {
        HelloWorldClient client = new HelloWorldClient("127.0.0.1", 50051);
        try {
            String user = "world";
            if (args.length > 0) {
                user = args[0];
            }
            client.greet(user);
        } finally {
            client.shutdown();
        }
    }

    public HelloWorldClient(String host, int port) {
        channel = ManagedChannelBuilder.forAddress(host, port)
                .usePlaintext()
                .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;
        try {
            response = blockingStub.sayHello(request);
        } catch (StatusRuntimeException e) {
            logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
            return;
        }
        logger.info("Message from gRPC-Server: " + response.getMessage());
    }

}

4.运行server和client

参考：【RPC基础系列3】gRPC简单示例