@Override
        public void handleEvent(Object event) throws GuacamoleException {
            if (event instanceof AuthenticationFailureEvent) {
                delegate.authenticationFailed((AuthenticationFailureEvent) event);
            }
        }
Handles an AuthenticationFailureEvent by passing the event to the delegate
listener. All other event types are ignored.

@param event
    An object that describes the event that occurred.

@throws GuacamoleException
     If thrown by the delegate listener.
guacamole/src/main/java/org/apache/guacamole/extension/ListenerFactory.java