I have, what I think to be, a very simple Spring WebSocket application. However, I'm trying to use path variables for the subscription as well as the message mapping.
I've posted a paraphrased example below. I would expect the @SendTo
annotation to return back to the subscribers based on their fleetId
. ie, a POST
to /fleet/MyFleet/driver/MyDriver
should notify subscribers of /fleet/MyFleet
, but I'm not seeing this behavior.
It's worth noting that subscribing to literal /fleet/{fleetId}
works. Is this intended? Am I missing some piece of configuration? Or is this just not how it works?
I'm not very familiar with WebSockets or this Spring project yet, so thanks in advance.
Controller.java
... @MessageMapping("/fleet/{fleetId}/driver/{driverId}") @SendTo("/topic/fleet/{fleetId}") public Simple simple(@DestinationVariable String fleetId, @DestinationVariable String driverId) { return new Simple(fleetId, driverId); } ...
WebSocketConfig.java
@Configuration @EnableWebSocketMessageBroker public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer { @Override public void configureMessageBroker(MessageBrokerRegistry config) { config.enableSimpleBroker("/topic"); config.setApplicationDestinationPrefixes("/live"); } @Override public void registerStompEndpoints(StompEndpointRegistry registry) { registry.addEndpoint("/fleet").withSockJS(); } }
index.html
var socket = new SockJS('/fleet'); var stompClient = Stomp.over(socket); stompClient.connect({}, function(frame) { // Doesn't Work stompClient.subscribe('/topic/fleet/MyFleet', function(greeting) { // Works stompClient.subscribe('/topic/fleet/{fleetId}', function(greeting) { // Do some stuff }); });
Send Sample
stompClient.send("/live/fleet/MyFleet/driver/MyDriver", {}, JSON.stringify({ // Some simple content }));
In order to tell Spring to forward client requests to the endpoint , we need to register the handler. Start the application- Go to http://localhost:8080 Click on start new chat it opens the WebSocket connection. Type text in the textbox and click send. On clicking end chat, the WebSocket connection will be closed.
The registerStompEndpoints() method registers the /gs-guide-websocket endpoint, enabling SockJS fallback options so that alternate transports can be used if WebSocket is not available.
setApplicationDestinationPrefixes("/app") - used to. Configure one or more prefixes to filter destinations targeting application annotated methods. When messages are processed, the matching prefix is removed from the destination in order to form the lookup path.
The Spring Framework provides support for using STOMP — a simple, messaging protocol originally created for use in scripting languages with frames inspired by HTTP. STOMP is widely supported and well suited for use over WebSocket and over the web.
Even though @MessageMapping
supports placeholders, they are not exposed / resolved in @SendTo
destinations. Currently, there's no way to define dynamic destinations with the @SendTo
annotation (see issue SPR-12170). You could use the SimpMessagingTemplate
for the time being (that's how it works internally anyway). Here's how you would do it:
@MessageMapping("/fleet/{fleetId}/driver/{driverId}") public void simple(@DestinationVariable String fleetId, @DestinationVariable String driverId) { simpMessagingTemplate.convertAndSend("/topic/fleet/" + fleetId, new Simple(fleetId, driverId)); }
In your code, the destination '/topic/fleet/{fleetId}' is treated as a literal, that's the reason why subscribing to it works, just because you are sending to the exact same destination.
If you just want to send some initial user specific data, you could return it directly in the subscription:
@SubscribeMapping("/fleet/{fleetId}/driver/{driverId}") public Simple simple(@DestinationVariable String fleetId, @DestinationVariable String driverId) { return new Simple(fleetId, driverId); }
Update: In Spring 4.2, destination variable placeholders are supported it's now possible to do something like:
@MessageMapping("/fleet/{fleetId}/driver/{driverId}") @SendTo("/topic/fleet/{fleetId}") public Simple simple(@DestinationVariable String fleetId, @DestinationVariable String driverId) { return new Simple(fleetId, driverId); }
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