How it works -- how the broker wire the publish-subscribe mapping internally?

Subject: How it works -- how the broker wire the publish-subscribe mapping internally?
Author: WebSpider
In response to: Configuration
Posted on: 07/11/2020 12:59:42 AM

@Controller
public class WebSocketController {

	// publisher send message to --> "/channel/chat"
	//       --> broker relay it to --> "/topic/messages"
        //       --> broker push it to all subscribers
	@MessageMapping("/chat")
	@SendTo("/topic/messages")
	public OutputMessage send(Message message) throws Exception {
	    String time = new SimpleDateFormat("HH:mm").format(new Date());
	    return new OutputMessage(message.getFrom(), message.getText(), time);
	}
}

>
> On 07/11/2020 12:58:05 AM WebSpider wrote:

@Configuration @EnableWebSocketMessageBroker public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer { @Override public void configureMessageBroker(MessageBrokerRegistry config) { config.enableSimpleBroker("/topic", "/queue"); config.setApplicationDestinationPrefixes("/channel"); } @Override public void registerStompEndpoints(StompEndpointRegistry registry) { registry.addEndpoint("/stomp").withSockJS(); } }

As the annoation @EnableWebSocketMessageBroker suggests, it will enable MESSAGE handling backed by a broker. Here:
".enableSimpleBroker" -- the simple built-in IN-MEMORY (Simple) message broker (Kafka can be a broker for production);
"/topic" -- the destination for subscribers -- a folder holding multiple sub-topics
"/channel" -- the destination for publishers -- a folder holding multiple sub-channels
"/stomp" -- the STOMP's endpoint for connection (STOMP: Simple Text-Orientated Messaging Protocol)

".withSockJS()" -- with SockJS as fallback if WebSocket is not supported by browser.

References:

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