GRPC的四种服务类型

上次简单介绍了grpc的使用方法，并创建了一个方法调用，在grpc中有四种服务类型，下面分别进行介绍

简单rpc

这就是一般的rpc调用，一个请求对象对应一个返回对象

proto语法：
rpc simpleHello(Person) returns (Result) {}

service代码
@Override
public void simpleHello(ProtoObj.Person request,
                  io.grpc.stub.StreamObserver responseObserver) {
    //返回结果
    responseObserver.onNext(ProtoObj.Result.newBuilder().setString("hello, "+request.getMyName()).build());
    responseObserver.onCompleted();
}

client代码
@Test
public void  simple() throws InterruptedException {

    final ManagedChannel channel = ManagedChannelBuilder.forAddress("127.0.0.1", 8080).usePlaintext(true).build();
    //定义同步阻塞的stub
    HelloServiceGrpc.HelloServiceBlockingStub blockingStub = HelloServiceGrpc.newBlockingStub(channel);

    ProtoObj.Person person = ProtoObj.Person.newBuilder().setMyName("World").build();
    //simple
    System.out.println("---simple rpc---");
    System.out.println(blockingStub.simpleHello(person).getString());
    channel.shutdown();
}

输出
---simple rpc---
hello, World

服务端流式rpc

一个请求对象，服务端可以传回多个结果对象

proto语法
rpc serverStreamHello(Person) returns (stream Result) {}

service代码
@Override
public void serverStreamHello(ProtoObj.Person request,
                        io.grpc.stub.StreamObserver responseObserver) {
    //返回多个结果
    responseObserver.onNext(ProtoObj.Result.newBuilder().setString("hello, "+request.getMyName()).build());
    responseObserver.onNext(ProtoObj.Result.newBuilder().setString("hello2, "+request.getMyName()).build());
    responseObserver.onNext(ProtoObj.Result.newBuilder().setString("hello3, "+request.getMyName()).build());
    responseObserver.onCompleted();
}

client代码
@Test
public void serverStream(){

    final ManagedChannel channel = ManagedChannelBuilder.forAddress("127.0.0.1", 8080).usePlaintext(true).build();
    //定义同步阻塞的stub
    HelloServiceGrpc.HelloServiceBlockingStub blockingStub = HelloServiceGrpc.newBlockingStub(channel);

    ProtoObj.Person person = ProtoObj.Person.newBuilder().setMyName("World").build();

    //server side
    System.out.println("---server stream rpc---");
    //返回结果是Iterator
    Iterator it = blockingStub.serverStreamHello(person);
    while (it.hasNext()) {
        System.out.print(it.next());
    }
    channel.shutdown();
}

输出
---server stream rpc---
string: "hello, World"
string: "hello2, World"
string: "hello3, World"

客户端流式rpc

客户端传入多个请求对象，服务端返回一个响应结果

proto语法
rpc clientStreamHello(stream Person) returns (Result) {}

service代码
@Override
public io.grpc.stub.StreamObserver clientStreamHello(
       final io.grpc.stub.StreamObserver responseObserver) {
   //返回observer应对多个请求对象
   return new StreamObserver(){
       private ProtoObj.Result.Builder builder=ProtoObj.Result.newBuilder();
       @Override
       public void onNext(ProtoObj.Person value) {
            builder.setString(builder.getString() +"," + value.getMyName());
       }

       @Override
       public void onError(Throwable t) {

       }

       @Override
       public void onCompleted() {
           builder.setString("hello"+builder.getString());
           responseObserver.onNext(builder.build());
           responseObserver.onCompleted();
       }
   };
}

client代码
@Test
public void clientStream() throws InterruptedException {
    final ManagedChannel channel = ManagedChannelBuilder.forAddress("127.0.0.1", 8080).usePlaintext(true).build();
    //定义异步的stub
    HelloServiceGrpc.HelloServiceStub asyncStub = HelloServiceGrpc.newStub(channel);
    ProtoObj.Person person = ProtoObj.Person.newBuilder().setMyName("World").build();

    //client side
    System.out.println("---client stream rpc---");
    StreamObserver responseObserver = new StreamObserver() {
        @Override
        public void onNext(ProtoObj.Result result) {
            System.out.println("client stream--" + result.getString());
        }

        @Override
        public void onError(Throwable t) {
        }

        @Override
        public void onCompleted() {
            //关闭channel
            channel.shutdown();
        }
    };
    StreamObserver clientStreamObserver = asyncStub.clientStreamHello(responseObserver);
    clientStreamObserver.onNext(ProtoObj.Person.newBuilder().setMyName("World").build());
    clientStreamObserver.onNext(ProtoObj.Person.newBuilder().setMyName("World2").build());
    clientStreamObserver.onCompleted();
    //由于是异步获得结果，所以sleep一秒
    Thread.sleep(1000);
}

输出
---client stream rpc---
client stream--hello,World,World2

双向流式rpc

结合客户端流式rpc和服务端流式rpc，可以传入多个对象，返回多个响应对象

proto语法
rpc biStreamHello(stream Person) returns (stream Result) {}

service代码
@Override
public io.grpc.stub.StreamObserver biStreamHello(
        final io.grpc.stub.StreamObserver responseObserver) {
    //返回observer应对多个请求对象
    return new StreamObserver(){
        private ProtoObj.Result.Builder builder=ProtoObj.Result.newBuilder();
        @Override
        public void onNext(ProtoObj.Person value) {
            responseObserver.onNext(ProtoObj.Result.newBuilder().setString("hello2, "+value.getMyName()).build());
            responseObserver.onNext(ProtoObj.Result.newBuilder().setString("hello3, "+value.getMyName()).build());
        }

        @Override
        public void onError(Throwable t) {
        }

        @Override
        public void onCompleted() {
            responseObserver.onCompleted();
        }
    };
}

client代码
@Test
public void bidirectStream() throws InterruptedException {

    final ManagedChannel channel = ManagedChannelBuilder.forAddress("127.0.0.1", 8080).usePlaintext(true).build();
    //定义异步的stub
    HelloServiceGrpc.HelloServiceStub asyncStub = HelloServiceGrpc.newStub(channel);

    ProtoObj.Person person = ProtoObj.Person.newBuilder().setMyName("World").build();

    //bi stream
    System.out.println("---bidirectional stream rpc---");
    StreamObserver  responseObserver = new StreamObserver() {
        @Override
        public void onNext(ProtoObj.Result result) {
            System.out.println("bidirectional stream--"+result.getString());
        }

        @Override
        public void onError(Throwable t) {
        }

        @Override
        public void onCompleted() {
            channel.shutdown();
        }
    };
    StreamObserver biStreamObserver=asyncStub.biStreamHello(responseObserver);
    biStreamObserver.onNext(ProtoObj.Person.newBuilder().setMyName("World").build());
    biStreamObserver.onNext(ProtoObj.Person.newBuilder().setMyName("World2").build());
    biStreamObserver.onCompleted();
    //由于是异步获得结果，所以sleep一秒
    Thread.sleep(1000);

}

输出
---bidirectional stream rpc---
bidirectional stream--hello2, World
bidirectional stream--hello3, World
bidirectional stream--hello2, World2
bidirectional stream--hello3, World2    

总结

grpc通过使用流式的方式，返回/接受多个实例可以用于类似不定长数组的入参和出参