gRPC学习记录(二)--Hello World

在上一篇的整体了解后,该篇则对应了快速上手,入门示例当然仍旧是Hello world,该一阶段不需要深究代码,所要求的的目的是先跑通,再回顾代码,然后分析需要什么知识,再去学什么.

1.Maven配置

首先是三个依赖包

 <properties>
        <grpc.version>1.0.3</grpc.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-netty</artifactId>
            <version>${grpc.version}</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-protobuf</artifactId>
            <version>${grpc.version}</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-stub</artifactId>
            <version>${grpc.version}</version>
        </dependency>
    </dependencies>

接着是转换工具

<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>
                    <protocArtifact>com.google.protobuf:protoc:3.1.0: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>

2.编写proto文件

在main目录下建立一个proto文件夹,然后在里面建立hello.proto,内容如下:

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 greetingsmessage HelloReply {  string message = 1;
}

接下来执行 mvn compile,就会生成如下代码,如果未被标记为源代码目录的话,就右键标记下:

Paste_Image.png

3.编写服务端代码

public class HelloWorldServer {    private int port = 50051;    private Server server;    /**
     * 启动服务
     * @throws IOException
     */
    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) {            //获取参数
            System.out.println("收到的信息:"+req.getName());            //这里可以放置具体业务处理代码 start

            //这里可以放置具体业务处理代码 end

            //构造返回
            HelloReply reply = HelloReply.newBuilder().setMessage(("Hello: " + req.getName())).build();
            responseObserver.onNext(reply);
            responseObserver.onCompleted();
        }
    }
}

4.编写客户端代码

public class HelloWorldClient {    private final ManagedChannel channel; //一个gRPC信道
    private final GreeterGrpc.GreeterBlockingStub blockingStub;//阻塞/同步 存根

   //初始化信道和存根
    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. */
    private HelloWorldClient(ManagedChannelBuilder<?> channelBuilder) {
        channel = channelBuilder.build();
        blockingStub = GreeterGrpc.newBlockingStub(channel);
    }    public void shutdown() throws InterruptedException {
        channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);
    }    //客户端方法
    public  void greet(String name){
        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
        HelloReply response;        try {
            response = blockingStub.sayHello(request);
        } catch (StatusRuntimeException e) {
            System.out.println("RPC调用失败:"+e.getMessage());            return;
        }
        System.out.println("服务器返回信息:"+response.getMessage());
    }    public static void main(String[] args) throws InterruptedException {
        HelloWorldClient client = new HelloWorldClient("127.0.0.1",50051);        try {            for(int i=0;i<5;i++){
                client.greet("world:"+i);
            }
        }finally {
            client.shutdown();
        }
    }
}

5.测试

服务端启动后,客户端访问

客户端:

Paste_Image.png

服务端:

Paste_Image.png

6.回顾分析

这一环节很重要,要对这个HelloWorld的Demo了解为什么跑通了.
回顾下在这个过程中做了哪些事情?
1.首先maven引入了三个依赖,分别是grpc-netty,grpc-protobuf,grpc-stub.应该是通讯,序列化,客户端调用三部分的东西吧.最后在build里面引入了一堆东西.
2.写proto文件,大概就是定义了一个服务接口的输入输出类型,然后利用build里面的工具,生成一堆代码.

//指定proto3格式syntax = "proto3";//一些生成代码的设置option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldProto";
option objc_class_prefix = "HLW";

package helloworld;//定义了一个serviceservice Greeter {  rpc SayHello (HelloRequest) returns (HelloReply) {}
}//定义了一个消息请求体message HelloRequest {  string name = 1;
}//定义了一个消息回复体message HelloReply {  string message = 1;
}

3.编写服务端
服务端有如下代码,可以看出这个接口和proto里面定义的接口是一致的.

private class GreeterImpl extends GreeterGrpc.GreeterImplBase{    public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {};
}

然后使用如下代码把该service绑定,

 server = ServerBuilder.forPort(port)
                              .addService(new GreeterImpl())
                              .build()
                              .start();

4.编写客户端代码
客户端通过如下方法创建了一个通信信道,然后和一个阻塞同步的通讯工具blockingStub.

//初始化信道和存根
    public HelloWorldClient(String host,int port){        this(ManagedChannelBuilder.forAddress(host, port)
                                  .usePlaintext(true));
    }    private HelloWorldClient(ManagedChannelBuilder<?> channelBuilder) {
        channel = channelBuilder.build();
        blockingStub = GreeterGrpc.newBlockingStub(channel);
    }

然后通过该blockingStub调用服务端方法.

 //客户端方法
    public  void greet(String name){
        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
        HelloReply response;        try {
            response = blockingStub.sayHello(request);
        } catch (StatusRuntimeException e) {
            System.out.println("RPC调用失败:"+e.getMessage());            return;
        }
        System.out.println("服务器返回信息:"+response.getMessage());
    }

接下来很自然的就去学proto3的一些相关知识了.

作者：此博废弃_更新在个人博客
链接：https://www.jianshu.com/p/46d600e5a1b1