Spring, how to broadcast message to connected clients using websockets?

java spring stomp
Michael picture Michael · Oct 20, 2014 · Viewed 9.2k times · Source

I am trying to use websockets in my app. I have followed this tutorial: http://spring.io/guides/gs/messaging-stomp-websocket/

It works perfectly.

When one of connected clients press button, this method is called:

@MessageMapping("/hello")
@SendTo("/topic/greetings")
public Greeting greeting() throws Exception {
    System.out.println("Sending message...");
    Thread.sleep(1000); // simulated delay
    return new Greeting("hello!");        
}

and message is broadcasted to all of connected clients.

Now i want to modify my server app, that it will broadcast messages periodically (each hour) to all of my connected clients, without interaction from clients.

Something like this(but this is not working obviously):

@Scheduled(fixedRate = 3600000)
public void sendMessage(){
   try {
   @SendTo("/topic/greetings")     
   greeting();
    } catch (Exception e) {
        e.printStackTrace(); 
    }
}

Thx for advices.

Answer

Artem Bilan picture Artem Bilan · Oct 20, 2014

@SendTo works only in the SimpAnnotationMethodMessageHandler, which is initiated only through the SubProtocolWebSocketHandler, hance when the WebSocketMessage is received from clients.

To achieve your requirements you should inject to the your @Scheduled service SimpMessagingTemplate brokerMessagingTemplate and use it directly:

@Autowired
private SimpMessagingTemplate brokerMessagingTemplate;
.......
this.brokerMessagingTemplate.convertAndSend("/topic/greetings", "foo");

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