背景：
接上篇 https://www.jianshu.com/p/c7d390efba29 中使用双向流 解决了grpc传输最大上限问题，避免了因为传输上限导致的错误，但是很显然没有将grpcServer的返回值传回页面，这篇文章我们来解决这个问题。
查看官方demo http://doc.oschina.net/grpc?t=60134页尾，找到
public void routeChat() throws Exception {
info("*** RoutChat");
final SettableFuture finishFuture = SettableFuture.create();
StreamObserver requestObserver =
asyncStub.routeChat(new StreamObserver() {
@Override
public void onNext(RouteNote note) {
info("Got message \"{0}\" at {1}, {2}", note.getMessage(), note.getLocation()
.getLatitude(), note.getLocation().getLongitude());
}
@Override
public void onError(Throwable t) {
finishFuture.setException(t);
}
@Override
public void onCompleted() {
finishFuture.set(null);
}
});
try {
RouteNote[] requests =
{newNote("First message", 0, 0), newNote("Second message", 0, 1),
newNote("Third message", 1, 0), newNote("Fourth message", 1, 1)};
for (RouteNote request : requests) {
info("Sending message \"{0}\" at {1}, {2}", request.getMessage(), request.getLocation()
.getLatitude(), request.getLocation().getLongitude());
requestObserver.onNext(request);
}
requestObserver.onCompleted();
finishFuture.get();
info("Finished RouteChat");
} catch (Exception t) {
requestObserver.onError(t);
logger.log(Level.WARNING, "RouteChat Failed", t);
throw t;
}
}
当然官方也只是解决了如何判定传输完了，那么我们改造一下
Code
GrpcServer
@GrpcService(HelloServiceGrpc.class)
public class HelloService extends HelloServiceGrpc.HelloServiceImplBase {
private static final Logger logger = LoggerFactory.getLogger(HelloService.class);
@Override
public StreamObserver sayHello(StreamObserver responseObserver) {
return new StreamObserver() {
@Override
public void onNext(HelloRequest value) {
String name = value.getName().toStringUtf8();
logger.info("received name :" + name);
}
@Override
public void onError(Throwable t) {
logger.warn("Encountered error in recordRoute", t);
}
@Override
public void onCompleted() {
responseObserver.onNext(HelloResponse.newBuilder().setMessage("welcome to gRPC").build());
//此处为了说明问题，返回两次Response
responseObserver.onNext(HelloResponse.newBuilder().setMessage(" second message ").build());
responseObserver.onCompleted();
}
};
}
}
客户端Controller
@RestController
public class HelloController {
@Autowired
private HelloService service;
@GetMapping("/hello")
public String sayHello(String name) {
return service.sendMessage(name);
}
}
客户端GrpcConfig
@Component
public class GrpcConfig {
@GrpcClient(value = "local-grpc-server")
private Channel channel;
@Bean("helloServiceStub")
public HelloServiceGrpc.HelloServiceStub getHelloServiceStub() {
return HelloServiceGrpc.newStub(channel);
}
}
客户端HelloService
@Service(value = "helloService")
public class HelloService{
@Autowired
private HelloServiceGrpc.HelloServiceStub helloServiceStub;
public String sendMessage(String name) {
StringBuffer stringBuffer = new StringBuffer();
final SettableFuture finalFuture =SettableFuture.create();
StreamObserver helloRequestStreamObservers = helloServiceStub.sayHello(
new StreamObserver() {
@Override
public void onNext(HelloResponse value) {
System.out.println("onNext : " + value.getMessage());
//将返回的内容全部追加到一个字符串中
stringBuffer.append(value.getMessage());
}
@Override
public void onError(Throwable t) {
finalFuture.setException(t);
}
@Override
public void onCompleted() {
finalFuture.set(null);
}
});
for (int i = 0; i < 10; i++) {
helloRequestStreamObservers.onNext(
HelloRequest.newBuilder()
.setName(ByteString.copyFrom(name,Charset.forName("UTF-8")))
.build()
);
}
helloRequestStreamObservers.onCompleted();
try {
finalFuture.get();
while(finalFuture.isDone()){
System.out.println("is done");
return stringBuffer.toString();
}
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
return null;
}
}
关于com.google.common.util.concurrent.SettableFuture源码，详细看这个帖子：https://blog.csdn.net/lb7758zx/article/details/74322074
接口请求结果
控制台执行顺序
第二种方式：通过HttpServletResponse直接写出
代码：
@RestController
public class HelloController {
@Autowired
private HelloService service;
@GetMapping("/hello")
public void sayHello(String name, HttpServletResponse response) {
service.sendMessage(name, response);
}
}
@Service(value = "helloService")
public class HelloService{
@Autowired
private HelloServiceGrpc.HelloServiceStub helloServiceStub;
public void sendMessage(String name, HttpServletResponse response) {
try {
final PrintWriter printWriter = response.getWriter();
final SettableFuture finalFuture =SettableFuture.create();
StreamObserver helloRequestStreamObservers = helloServiceStub.sayHello(
new StreamObserver() {
@Override
public void onNext(HelloResponse value) {
System.out.println("onNext : " + value.getMessage());
if(null != printWriter){
printWriter.write(value.getMessage());
}
}
@Override
public void onError(Throwable t) {
finalFuture.setException(t);
}
@Override
public void onCompleted() {
finalFuture.set(null);
}
});
for (int i = 0; i < 10; i++) {
helloRequestStreamObservers.onNext(
HelloRequest.newBuilder()
.setName(ByteString.copyFrom(name,Charset.forName("UTF-8")))
.build()
);
}
helloRequestStreamObservers.onCompleted();
//阻塞，等待通知
finalFuture.get();
if(finalFuture.isDone()){
printWriter.close();
}
} catch (InterruptedException | ExecutionException | IOException e) {
e.printStackTrace();
}
}
}
效果和上面基本一致，大家根据需要，自行参考，欢迎多多交流。
原创帖，转载注明出处！