Quick start gRPC

环境配置

JDK7及其以上

获取实例代码

$ git clone -b v1.42.1 https://github.com/grpc/grpc-java

进入examples文件夹

cd grpc-java/examples

启动实例代码

1.编译客户端实例代码和服务端实例代码

$ ./gradlew installDist

2.启动服务端

$ ./build/install/examples/bin/hello-world-server
INFO: Server started, listening on 50051

3.开启另外一个终端窗口，启动客户端

$ ./build/install/examples/bin/hello-world-client
INFO: Will try to greet world ...
INFO: Greeting: Hello world

输出上面的提示信息，就说明已经运行成功了。

第一个gRPC服务

接下来，我们以官方案例的为基础，尝试着写一个简单的服务。gRPC的服务需要先在protocol buffers 里定义。在上面的例子中，服务端和客户端都有个sayHello() RPC方法，服务端从客户端里接受了一个HelloRequest消息后，返回了HelloReply消息。这个SayHello()的定义如下：

// 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;
}

我们打开src/main/proto/helloworld.proto 文件，添加一个新的方法SayHelloAgain()。

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

(IDEA 只需打开example目录即可)

然后点编译，gRPC会重写GreeterGrpc.java，找到这个类

会发现它多出了我们新写的方法。

更新服务端和客户端代码

打开 src/main/java/io/grpc/examples/helloworld/HelloWorldServer.java 增加新的方法的调用。

  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();
    }
 
    public void sayHelloAgain(HelloRequest req,StreamObserver<HelloReply> responseObserver){
      HelloReply reply = HelloReply.newBuilder().setMessage("Hello again " + req.getName()).build();
      responseObserver.onNext(reply);
      responseObserver.onCompleted();
    }
  }

打开src/main/java/io/grpc/examples/helloworld/HelloWorldClient.java，在greet方法中新增sayHelloAgain()的调用

    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.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
            return;
        }
        logger.info("Greeting: " + response.getMessage());
 
        try {
            response = blockingStub.sayHelloAgain(request);
        } catch (StatusRuntimeException e) {
            logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
            return;
        }
        logger.info("Greeting: " + response.getMessage());
    }

重新启动项目

 ./gradlew installDist

启动服务端

$ ./build/install/examples/bin/hello-world-server
INFO: Server started, listening on 50051

打开一个新的终端，启动客户端

$ ./build/install/examples/bin/hello-world-client
INFO: Will try to greet world ...
INFO: Greeting: Hello world
INFO: Greeting: Hello again world

输出了新的提示

INFO: Greeting: Hello again world

这个例子就完成了。