[[websocket-stomp-websocket-scope]]
= WebSocket Scope

Each WebSocket session has a map of attributes. The map is attached as a header to inbound
client messages and may be accessed from a controller method, as the following example shows:

[source,java,indent=0,subs="verbatim,quotes"]
----
@Controller
public class MyController {

	@MessageMapping("/action")
	public void handle(SimpMessageHeaderAccessor headerAccessor) {
		Map<String, Object> attrs = headerAccessor.getSessionAttributes();
		// ...
	}
}
----

You can declare a Spring-managed bean in the `websocket` scope.
You can inject WebSocket-scoped beans into controllers and any channel interceptors
registered on the `clientInboundChannel`. Those are typically singletons and live
longer than any individual WebSocket session. Therefore, you need to use
WebSocket-scoped beans in proxy mode, conveniently defined with `@WebSocketScope`:

[source,java,indent=0,subs="verbatim,quotes"]
----
	@Component
	@WebSocketScope
	public class MyBean {

		@PostConstruct
		public void init() {
			// Invoked after dependencies injected
		}

		// ...

		@PreDestroy
		public void destroy() {
			// Invoked when the WebSocket session ends
		}
	}

	@Controller
	public class MyController {

		private final MyBean myBean;

		@Autowired
		public MyController(MyBean myBean) {
			this.myBean = myBean;
		}

		@MessageMapping("/action")
		public void handle() {
			// this.myBean from the current WebSocket session
		}
	}
----

As with any custom scope, Spring initializes a new `MyBean` instance the first
time it is accessed from the controller and stores the instance in the WebSocket
session attributes. The same instance is subsequently returned until the session
ends. WebSocket-scoped beans have all Spring lifecycle methods invoked, as
shown in the preceding examples.
