How to send message to a specific subscription over spring websocket STOMP? - spring

Question

I am using STOMP over websockets with spring boot. Is there a possibility to send a message to a specific subscription? I subscribe to the STOMP endpoints using a STOMP header containing an id field according to the stomp documentation I want this id to be used to determine the clients who should receive a message, but spring seems not to use this id. I can not just use sendToUser because two clients can have the same user id e.g. if a user has two opened browser windows. Only one specific window should receive the message.
In the following example I have two connected clients which are using the same user, but different ids in the STOMP header.
Client1-ID: a32d66bf-03c7-47a4-aea0-e464c0727842
Client2-ID: b3673d33-1bf2-461e-8df3-35b7af07371b
In spring I have executed the following Kotlin code:
val subscriptions = userRegistry.findSubscriptions {
it.destination == "/user/topic/operations/$operationId/runs"
}
subscriptions.forEach{
println("subscription id: ${it.id}");
println("session id: ${it.session.id}");
println("user id ${it.session.user.name}");
}
The output:
subscription id: sub-7
session id: mcjpgn2i
user id 4a27ef88-25eb-4175-a872-f46e7b9d0564
subscription id: sub-7
session id: 0dxuvjgp
user id 4a27ef88-25eb-4175-a872-f46e7b9d0564
There is no sign of the id I have passed to the stomp header.
Is it possible to send a message to one specific subscription determined by the id I have passed with the header?

Answer 1

I got it working.
First of all, there was something wrong with my client setup. I have set the subscription id in the connection header like this:
this.stompClient.webSocketFactory = (): WebSocket => new SockJS("/ws");
this.stompClient.connectHeaders = { id: subscriptionId };
this.stompClient.activate();
But the subscription header has to be set in the subscription header:
this.stompClient.subscribe(this.commonEndpoint,
this.onMessageReceived.bind(this),
{ id: subScriptionId });
If I do this, spring is correctly using this id as the subscription id, instead of using some default like sub-7.
According to that thread I can send messages to specific sessions instead of user.
With the following code I can send a message to a specific subscription:
val subscriptions = userRegistry.findSubscriptions {
it.destination == "/user/topic/operations/$operationId/runs"
}
subscriptions.forEach {
if(it.id === mySubscriptionId){
val headerAccessor =
SimpMessageHeaderAccessor.create(SimpMessageType.MESSAGE)
headerAccessor.sessionId = it.session.id
headerAccessor.setLeaveMutable(true)
simpMessagingTemplate.convertAndSendToUser(it.session.id,
"/topic/operations/runs", messageResponseEntity,
headerAccessor.getMessageHeaders())
}
}

Answer 2

I'm able to send message to a specific subscription using SimpMessagingTemplate.
#Autowired
private final SimpMessagingTemplate messagingTemplate;
public void sendMessage(String simpUserId, String destination, String message) {
try {
messagingTemplate.convertAndSendToUser(simpUserId, destination, message);
} catch (Exception ex) {
LOG.error("Exception occurred while sending message [message={}]", ex.getMessage(), ex);
}
}
You may refer SimpMessagingTemplate.convertAndSendToUser