Grpc系列一 第一个hello world 例子

1. 概念

gRPC的定义：

• 一个高性能、通用的开源RPC框架
• 主要面向移动应用开发： gRPC提供了一种简单的方法来精确地定义服务和为iOS、Android和后台支持服务自动生成可靠性很强的客户端功能库。
• 基于HTTP/2协议标准而设计，基于ProtoBuf(Protocol Buffers)序列化协议开发
• 支持众多开发语言

2. Hello world Demo

主要流程：
1. 通过.proto文件定义服务
2. 通过protocol buffer compiler插件生成客户端和服务端
3. 通过grpc API生成客户端和服务端代码

2.1 定义RPC服务 proto

// 如果使用此注释，则使用proto3; 否则使用proto2syntax = "proto3";// 生成类的包名option java_package = "com.hry.spring.grpc.simple";//生成的数据访问类的类名，如果没有指定此值，则生成的类名为proto文件名的驼峰命名方法option java_outer_classname = "GreeterEntity";option java_multiple_files = true;service Greeter {  rpc SayHello (HelloRequest) returns (HelloReply) {}}message HelloRequest {  string name = 1;}message HelloReply {  string message = 1;}

2.2 生成基础类

通过proto里的方法生成基础类
通过Protobuf3 的第一个Java demo的步骤生成protobuf3相关代码，如HelloReply,HelloReplyOrBuilder,HelloRequest,HelloRequestOrBuilder，详细见github代码
生成GreeterGrpc

a. 配置pom.xml，指定proto文件

<!-- grpc 依赖jar --><dependency>    <groupId>io.grpc</groupId>    <artifactId>grpc-netty</artifactId>    <version>1.3.0</version></dependency><dependency>    <groupId>io.grpc</groupId>    <artifactId>grpc-protobuf</artifactId>    <version>1.3.0</version></dependency><dependency>    <groupId>io.grpc</groupId>    <artifactId>grpc-stub</artifactId>    <version>1.3.0</version></dependency><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.springframework.boot</groupId>            <artifactId>spring-boot-maven-plugin</artifactId>        </plugin>        <!-- 根据proto文件生成java -->        <plugin>            <groupId>org.xolstice.maven.plugins</groupId>            <artifactId>protobuf-maven-plugin</artifactId>            <version>0.5.0</version>            <configuration>                <protocArtifact>com.google.protobuf:protoc:3.2.0:exe:${os.detected.classifier}</protocArtifact>                <pluginId>grpc-java</pluginId>                <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.3.0:exe:${os.detected.classifier}</pluginArtifact>                <protoSourceRoot>src/main/resources/com/hry/spring/grpc/simple/</protoSourceRoot>            </configuration>            <executions>                <execution>                    <goals>                        <goal>compile</goal>                        <goal>compile-custom</goal>                    </goals>                </execution>            </executions>        </plugin>    </plugins></build>

b. 执行pom.xml，在target/generated-sources/protobuf/grpc-java/com/hry/spring/grpc/simple/ 目录GreeterGrpc.java
GreeterGrpc封装基本的GRPC功能，后续的客户端和服务端都从这个类引申出来。GreeterGrpc类见gibhub

2.3 服务端

服务端代码

public class HelloWorldServer {    private static final Logger logger = LoggerFactory.getLogger(HelloWorldServer.class);    private Server server;    private void start() throws IOException {        /* The port on which the server should run */        int port = 50051;        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() {                // Use stderr here since the logger may have been reset by its                // JVM shutdown hook.                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();        }    }    /**     * Await termination on the main thread since the grpc library uses daemon     * threads.     */    private void blockUntilShutdown() throws InterruptedException {        if (server != null) {            server.awaitTermination();        }    }    /**     * Main launches the server from the command line.     */    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) {            HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + req.getName()).build();            responseObserver.onNext(reply);            responseObserver.onCompleted();        }    }}

2.4 客户端

客户端主代码

public class HelloWorldClient {    private static final Logger logger =  LoggerFactory.getLogger(HelloWorldClient.class);    private final ManagedChannel channel;    private final GreeterGrpc.GreeterBlockingStub blockingStub;    /**     * Construct client connecting to HelloWorld server at {@code host:port}.     */    public HelloWorldClient(String host, int port) {        this(ManagedChannelBuilder.forAddress(host, port)                // Channels are secure by default (via SSL/TLS). For the example                // we disable TLS to avoid                // needing certificates.                .usePlaintext(true));    }    /**     * Construct client for accessing RouteGuide server using the existing     * channel.     */    HelloWorldClient(ManagedChannelBuilder<?> channelBuilder) {        channel = channelBuilder.build();        blockingStub = GreeterGrpc.newBlockingStub(channel);    }    public void shutdown() throws InterruptedException {        channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);    }    /** Say hello to server. */    public 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.error("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 {            String user = "world";            if (args.length > 0) {                user = args[0];             }            client.greet(user);        } finally {            client.shutdown();        }    }}

2.4 运行

先运行服务端，再运行客户端，关键日志打印如下：

21:35:35.208 [main] INFO com.hry.spring.grpc.simple.HelloWorldClient - Will try to greet world ...21:35:35.847 [main] INFO com.hry.spring.grpc.simple.HelloWorldClient - Greeting: Hello world

3. 代码

见github代码