Spring Websocket - How can I detect client disconnect - spring

Question

I am new to spring
I have this class :
public class Server extends TextWebSocketHandler implements WebSocketHandler {
WebSocketSession clientsession;
#Override
public void handleTextMessage(WebSocketSession session, TextMessage message) {
clientsession = session;
}
I need to detect a client disconnect on clientsession.
implement ApplicationListener but its not clear how I can register the listener?
do I need to do it in my web.xml ?

Answer 1

The WebSocketHandler afterConnectionClosed function is called after a websocket client disconnects. You simply need to override this in the manner that you override handleTextMessage.
#Override
public void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus){
// your code here
}
There may be substantial delay between the client disconnect and your server event detection. See details about real-time disconnection detection.

Answer 2

You will need to override configureClientOutboundChannel and configureClientInboundChannel of AbstractWebSocketMessageBrokerConfigurer, providing your interceptor
Another way is using ApplicationEvents.
Both methods are described here:
http://www.sergialmar.com/2014/03/detect-websocket-connects-and-disconnects-in-spring-4/
public class StompConnectEvent implements ApplicationListener<SessionConnectEvent> {
private final Log logger = LogFactory.getLog(StompConnectEvent.class);
public void onApplicationEvent(SessionConnectEvent event) {
StompHeaderAccessor sha = StompHeaderAccessor.wrap(event.getMessage());
String company = sha.getNativeHeader("company").get(0);
logger.debug("Connect event [sessionId: " + sha.getSessionId() +"; company: "+ company + " ]");
}
}
I hope that help. Let me know if I need to explain more.

Answer 3

You can use listeners to detect when session is connected or closed.
More information about listeners you can find by this link.
Example how to detect connected session:
#Component
public class SessionConnectedEventListener implements ApplicationListener<SessionConnectedEvent> {
private IWebSocketSessionService webSocketSessionService;
public SessionConnectedEventListener(IWebSocketSessionService webSocketSessionService) {
this.webSocketSessionService = webSocketSessionService;
}
#Override
public void onApplicationEvent(SessionConnectedEvent event) {
webSocketSessionService.saveSession(event);
}
}
Example how to detect when session is disconneted:
#Component
public class SessionDisconnectEventListener implements ApplicationListener<SessionDisconnectEvent> {
private IWebSocketSessionService webSocketSessionService;
public SessionDisconnectEventListener(IWebSocketSessionService webSocketSessionService) {
this.webSocketSessionService = webSocketSessionService;
}
#Override
public void onApplicationEvent(SessionDisconnectEvent event) {
webSocketSessionService.removeSession(event);
}
}

Answer 4

What you probably want to achieve is maintaining multiple sessions. Something like this:
public class Server extends TextWebSocketHandler implements WebSocketHandler {
private List<WebSocketSession> sessions = new ArrayList<>();
#Override
public void afterConnectionEstablished(WebSocketSession session) {
sessions.add(session);
}
#Override
public void afterConnectionClosed(WebSocketSession session, CloseStatus status) {
sessions.remove(session);
}
#Override
public void handleTextMessage(WebSocketSession session, TextMessage message) {
// clientsession = session;
// Send individual or broadcast messages here ...
session.sendMessage(new TextMessage(textMessage + "!"));
}
}