I'm facing the following problem and I found no working solution yet.
I have 3 different applications that should communicate with each other:
the UI part (1)
the backend application (2)
the microservice "in the cloud" (3)
The backend application provides a Webservice (REST) for the UI to get and put information from/to the microservice.
Everything I want to grab from the microservice works fine, but:
If I want to put data to the microservice, the specs require a websocket connection. This works fine too, but the microservice returns a message after the (un-)successful command, like
{"statusCode":200,"messageId":"1234567890"}
The problem now is: How can I grab this message in my application and send it back to the UI, so the user knows if the command was successful?
For the moment I tried this:
WebSocketClient.java
#OnMessage
public void onMessage(Session session, String msg) {
if (this.messageHandler != null) {
this.messageHandler.handleMessage(msg);
}
}
public void addMessageHandler(MessageHandler msgHandler) {
this.messageHandler = msgHandler;
}
public static interface MessageHandler {
public String handleMessage(String message);
}
MyTotalAwesomeController.java
public class MyTotalAwesomeController {
WebSocketClient wsc = new WebSocketClient();
...
#RequestMapping(value="/add", method={RequestMethod.POST, RequestMethod.OPTIONS})
public ResponseEntity<Object> putDataToMicroservice(#RequestBody Map<String, Object> payload, #RequestHeader(value = "authorization") String authorizationHeader) throws Exception {
...
wsc.addMessageHandler(new WebSocketClient.MessageHandler() {
public String handleMessage(String message) {
System.out.println("RETURN MSG FROM WSS : " + message);
return message;
}
});
return ResponseEntity.ok("worked");
}
I can see the console output from the MessageHandler return, but I don't know how I can pass this to the parent method for return insted of just returning the ResponseEntity.ok().
I'm not very used to WebSocket connections in Java yet, so please don't judge me ;-)
Thank you for your help.
The code below will work under the assumption that the #OnMessage method is executed in a thread managed by the WebSocket client runtime. Please inspect the thread that runs the #OnMessage method.
If the above premise is true, the putDataToMicroservice() method, executed by a thread in the global scope, will wait until the WebSocket response arrives at the WS client thread, which will repass the message to the global scope thread. Then the execution in your controller class will continue.
public class MyTotalAwesomeController {
WebSocketClient wsc = new WebSocketClient();
// Queue for communication between threads.
private BlockingQueue<String> queue;
#PostConstruct
void init() {
queue = new SynchronousQueue<>(true);
// This callback will be invoked by the WebSocket thread.
wsc.addMessageHandler(new WebSocketClient.MessageHandler() {
#Override
public String handleMessage(String message) {
System.out.println("RETURN MSG FROM WSS : " + message);
// Pass message to the controller thread.
queue.put(message);
// Note that the return value is not necessary.
// You can take it out of the interface as well.
return null;
}
});
}
#RequestMapping(value="/add", method={RequestMethod.POST, RequestMethod.OPTIONS})
public ResponseEntity<Object> putDataToMicroservice(#RequestBody Map<String, Object> payload, #RequestHeader(value = "authorization") String authorizationHeader) throws Exception {
// At this point you make a WebSocket request, is that right?
doWebSocketRequest();
// This poll call will block the current thread
// until the WebSocket server responds,
// or gives up waiting after the specified timeout.
//
// When the WebSocket server delivers a response,
// the WS client implementation will execute the
// #OnMessage annotated method in a thread
// managed by the WS client itself.
//
// The #OnMessage method will pass the message
// to this thread in the queue below.
String message = queue.poll(30, TimeUnit.SECONDS);
if (message == null) {
// WebSocket timeout.
}
return ResponseEntity.ok("worked");
}
}
Related
I would like to subscribe and receive any events using objects instead of strings when using Spring Boot WebSockets. If my method returns a string and I use the StringMessageConverter my code successfully listens for the /topic/rooms/created event.
If I return a Room object instead and use MappingJackson2MessageConverter then my subscription no longer receives any messages.
#MessageMapping("/rooms/create/{roomName}")
#SendTo("/topic/rooms/created")
#CrossOrigin(origins = "http://localhost:3000")
public Room createRoom(#DestinationVariable final String roomName) {
return roomService.createRoom(roomService.getRooms().size(), roomName);
}
This sends the message and creates the room successfully. The response isn't picked up by the subscription.
final String roomName = "RoomName";
final StompSession.Subscription subscription = stompSession.subscribe("/topic/rooms/created", new StompFrameHandler() {
#Override
public Type getPayloadType(final StompHeaders headers) {
return Room.class;
}
#Override
public void handleFrame(StompHeaders headers, Object payload) {
// Not called
System.out.println("Received message");
}
});
System.out.println("Sending message");
stompSession.send("/app/rooms/create/" + roomName, null);
I've also tried creating a Room instance and using a jackson object mapper to convert to JSON with no issues.
How can I resolve this?
I'm looking to trigger two messages sent back to a micro service from the one call.
I want the response to be sent firstly (its an acceptance message) and then the contents from the sendPort2Response method to be sent, the current functionality sends the response last - is this even possible to do?
public Port2RequestResponse processPort2Request(Port2Request request) {
FMNP getFMNPRequestObject = unmarshalInputRequest(request.getXmlPortMessage());
Port2RequestResponse response = new Port2RequestResponse();
response.setResult(getSuccessResponse(getFMNPRequestObject.getPort().getDonor()));
Thread t = new Thread(){
#SneakyThrows
#Async
public void run(){
sendPort2Response(request);
Thread.sleep(10000);
}
};
t.start();
return response;
}
I'm new to Spring Boot and web applications. I have to send notifications of unhandled/unread messages from a Spring Boot backend to a web client. I decided to use Server Sent Events since I think I don't need a bidirectional connection (otherwise I'd have thought of WebSockets).
I made a very simple REST controller which finds all unhandled messages in a db and sends them to the client. The problem is that it keeps sending forever all the messages, while I'd like to send a message only when it is added to the db, or when the client first connects to the server.
The behaviour I'd like to achieve is similar to a mail client or a messaging app, in which the user is notifyed not only on new messages but also of previous ones if he/she didn't mark them as read. The notification should happen only once when the client connects, not loop forever.
Here is my code:
#RestController
#CrossOrigin(origins = "*")
public class SseEmitterController {
private MessageDAO messageDAO;
private ExecutorService nonBlockingService = Executors
.newCachedThreadPool();
#Autowired
public SseEmitterController(MessageDAO messageDAO) {
this.messageDAO = messageDAO;
}
#GetMapping("/incoming_messages")
public SseEmitter handleSse() {
SseEmitter emitter = new SseEmitter();
nonBlockingService.execute(() -> {
try {
List<Message> messages = messageDAO.findByHandledFalse();
for (Message message: messages) {
emitter.send(message, MediaType.APPLICATION_JSON);
}
emitter.complete();
} catch (Exception ex) {
emitter.completeWithError(ex);
}
});
return emitter;
}
}
I know that the problem is caused by the fact that I query the db inside handleSse method, but I couldn't figure out how to do it outside.
Could you please help me?
Update October 05, 2021
I found out how to solve the problem, I didn't update the question because I didn't have the time, but since someone asked me to do so in the comments, I'm gonna explain my solution, hoping it may be helpful.
Here's my code:
The SseEmitterController is responsible for invoking the SseService on frontend's request:
#RestController
#CrossOrigin(origins = "*")
public class SseEmitterController {
private final SseService sseService;
#Autowired
SseEmitterController(SseService sseService) {
this.sseService = sseService;
}
#GetMapping("/incoming_messages")
public ResponseEntity<SseEmitter> handleSse() {
final SseEmitter emitter = new SseEmitter();
sseService.addEmitter(emitter);
emitter.onCompletion(() -> sseService.removeEmitter(emitter));
emitter.onTimeout(() -> sseService.removeEmitter(emitter));
return new ResponseEntity<>(emitter, HttpStatus.OK);
}
}
The SseService is called on a new message arrival (from another part of the application) and sends the notification (actually a server sent event) to the frontend (which previously called the endpoint in the controller above.
The service is called like so: sseService.sendHelpRequestNotification(helpRequest);
#Service
public class SseService {
private final List<SseEmitter> emitters = new CopyOnWriteArrayList<>();
public void addEmitter(final SseEmitter emitter) {
emitters.add(emitter);
}
public void removeEmitter(final SseEmitter emitter) {
emitters.remove(emitter);
}
public void sendMessagesNotification(Message message) {
List<SseEmitter> sseEmitterListToRemove = new ArrayList<>();
emitters.forEach((SseEmitter emitter) -> {
try {
emitter.send(message, MediaType.APPLICATION_JSON);
} catch (Exception e) {
sseEmitterListToRemove.add(emitter);
}
});
emitters.removeAll(sseEmitterListToRemove);
}
}
And finally there is another controller to get all previous unhandled messages (not involving server sent events):
#GetMapping(value = "/unhandled_help_requests")
public ResponseEntity<List<HelpRequest>> getUnhandledMessages() {
List<Message> resultSet = messageDAO.findByHandledFalse(Sort.by("date").and(Sort.by("time")));
return new ResponseEntity<>(resultSet, HttpStatus.OK);
}
So, to sum it up: the frontend calls the SseEmitterController to listen for new SSEs. These SSEs are created and sent whenever a new message arrives to the backend, via the SseService. Finally, to get all unhandled (for whatever reason) messages, there is a specific old fashioned controller.
I am new with Spring Integration. I was making some tests I realized the behavior of my app changes when the Gateway return void or return String. I'm trying to process the flow in the background (async) meanwhile I return a http message. So I did a async pipeline
#Bean
MessageChannel asyncChannel() {
return new QueueChannel(1);
}
#Bean
public MessageChannel asyncChannel2() {
return new QueueChannel(1);
}
#Bean
public MessageChannel asyncChannel3() {
return new QueueChannel(1);
}
#Bean(name = PollerMetadata.DEFAULT_POLLER)
PollerMetadata customPoller() {
PeriodicTrigger periodicTrigger = new PeriodicTrigger(2000, TimeUnit.MICROSECONDS);
periodicTrigger.setFixedRate(true);
periodicTrigger.setInitialDelay(1000);
PollerMetadata poller = new PollerMetadata();
poller.setMaxMessagesPerPoll(500);
poller.setTrigger(periodicTrigger);
return poller;
}
3 Activators
#ServiceActivator(inputChannel = "asyncChannel", outputChannel = "asyncChannel2")
public String async(String message) {
try {
Thread.sleep(5000);
log.info("Activator 1 " + message);
return message;
} catch (InterruptedException e) {
log.error("I don't want to sleep now");
}
return "";
}
#ServiceActivator(inputChannel = "asyncChannel2", outputChannel = "asyncChannel3")
public String async(String message){
log.info("Activator 2 "+ message);
try {
Thread.sleep(2000);
return message;
} catch (InterruptedException e) {
log.error("I don't want to sleep");
}
return "";
}
#ServiceActivator(inputChannel = "asyncChannel3")
public String result(String message) throws InterruptedException {
Thread.sleep(2000);
log.info("Activator 3 " + message);
return message;
}
I receive a message from Controller class
private final ReturningGateway returningGateway;
#PostMapping("/example")
public ResponseEntity post() {
returningGateway.processWhileResponse("Message example");
return ResponseEntity.ok(Map.of("Message","Http Done. Check the logs"));
}
The gateway
#Gateway(requestChannel = "asyncChannel")
public void processWhileResponse(String message_example);
The curious thing is when the gateway returns a void it making the process async so I can see the http message "Http Done. Check the logs" first, then I go to the logs and I see the async execution. but when the gateway returns a String I see the logs first and then the http message.
So I need the gateway returns a value but it keep the async way so I can get a http message
could you give a hand?
Sorry if I'm not using the right term. Thanks
So I need the gateway returns a value but it keep the async way so I can get a http message.
As long as you return some non-async type, it is going to block your code on the gateway call and wait for that return value to come back. Even if your flow behind that gateway is async, it still waits for a reply on the CountDownLatch barrier for replyChannel. In case of void return type there is no reply expectations and gateway exists immediately after sending a request message.
You may consider to have a Future as return type, but it still not clear when you would like to get the value: before returning from your controller method, or it is OK already after.
See more info in docs: https://docs.spring.io/spring-integration/docs/current/reference/html/messaging-endpoints.html#async-gateway
I want to pass messages to bus via REST, and get it back. But I cant correctly setup the message bus receiver, it throws java.lang.IllegalStateException: Response has already been written. In real life message bus should receive messages from different sources and pass a message to another target. Therefore we just need to publish the message to the bus. But how to correctly read messages and handle all of them? For example from a REST interface: read that messages!
My simple app start:
public static void main(String[] args) {
Vertx vertx = Vertx.vertx();
vertx.deployVerticle(new RESTVerticle());
vertx.deployVerticle(new Receiver());
EventBus eventBus = vertx.eventBus();
eventBus.registerDefaultCodec(MessageDTO.class, new CustomMessageCodec());
}
REST part
public class RESTVerticle extends AbstractVerticle {
private EventBus eventBus = null;
#Override
public void start() throws Exception {
Router router = Router.router(vertx);
eventBus = vertx.eventBus();
router.route().handler(BodyHandler.create());
router.route().handler(CorsHandler.create("*")
.allowedMethod(HttpMethod.GET)
.allowedHeader("Content-Type"));
router.post("/api/message").handler(this::publishToEventBus);
// router.get("/api/messagelist").handler(this::getMessagesFromBus);
router.route("/*").handler(StaticHandler.create());
vertx.createHttpServer().requestHandler(router::accept).listen(9999);
System.out.println("Service running at 0.0.0.0:9999");
}
private void publishToEventBus(RoutingContext routingContext) {
System.out.println("routingContext.getBodyAsString() " + routingContext.getBodyAsString());
final MessageDTO message = Json.decodeValue(routingContext.getBodyAsString(),
MessageDTO.class);
HttpServerResponse response = routingContext.response();
response.setStatusCode(201)
.putHeader("content-type", "application/json; charset=utf-8")
.end(Json.encodePrettily(message));
eventBus.publish("messagesBus", message);
}
And the Receiver: I move it to a different class, but it does not help
public class Receiver extends AbstractVerticle {
#Override
public void start() throws Exception {
EventBus eventBus = vertx.eventBus();
Router router = Router.router(vertx);
router.route().handler(BodyHandler.create());
router.route().handler(CorsHandler.create("*")
.allowedMethod(HttpMethod.GET)
.allowedHeader("Content-Type"));
router.get("/api/messagelist").handler(this::getMessagesFromBus);
router.route("/*").handler(StaticHandler.create());
vertx.createHttpServer().requestHandler(router::accept).listen(9998);
System.out.println("Service Receiver running at 0.0.0.0:9998");
private void getMessagesFromBus(RoutingContext routingContext) {
EventBus eventBus = vertx.eventBus();
eventBus.consumer("messagesBus", message -> {
MessageDTO customMessage = (MessageDTO) message.body();
HttpServerResponse response = routingContext.response();
System.out.println("Receiver ->>>>>>>> " + customMessage);
if (customMessage != null) {
response.putHeader("content-type", "application/json; charset=utf-8")
.end(Json.encodePrettily(customMessage));
}
response.closed();
});
}
So if i post message to REST and handler publish it to the bus, when I am runtime get http://localhost:9998/api/messagelist it is return json, but second time it trow exception
java.lang.IllegalStateException: Response has already been written
at io.vertx.core.http.impl.HttpServerResponseImpl.checkWritten(HttpServerResponseImpl.java:561)
at io.vertx.core.http.impl.HttpServerResponseImpl.putHeader(HttpServerResponseImpl.java:154)
at io.vertx.core.http.impl.HttpServerResponseImpl.putHeader(HttpServerResponseImpl.java:52)
at com.project.backend.Receiver.lambda$getMessagesFromBus$0(Receiver.java:55)
at io.vertx.core.eventbus.impl.HandlerRegistration.handleMessage(HandlerRegistration.java:207)
at io.vertx.core.eventbus.impl.HandlerRegistration.handle(HandlerRegistration.java:201)
at io.vertx.core.eventbus.impl.EventBusImpl.lambda$deliverToHandler$127(EventBusImpl.java:498)
at io.vertx.core.impl.ContextImpl.lambda$wrapTask$18(ContextImpl.java:335)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:358)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:357)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:112)
at java.lang.Thread.run(Thread.java:745)
Receiver ->>>>>>>> Message{username=Aaaewfewf2d, message=41414wefwef2d2}
How to correctly get all messages from the receiver? Or if the bus received messages, should I immediately store them to the db? Can a message bus keep messages and not lost them?
Thanks
Each hit in the entry point "/api/messagelist" creates one new consumer with the request routing context.
The first request will create the consumer and reply to the request. When the second message was published, that consumer will receive the message and will reply to the previous request (instance) and this was closed.
I think that you misunderstood the event bus purpose and I really recommend you to read the documentation.
http://vertx.io/docs/vertx-core/java/#event_bus
I did not had the chance to test your code but it seems that the publish operation is throwing an exception and vertx will try to send back an error message. However you already replied and ended the connection.
Now the error might be from your codec but due to the asynchronous nature of vertx you only see it at a later stage and mangled with the internal error handler.