@MessageMapping("/getNotifications")
@SendTo("/topic/notifications")
public @ResponseBody List<NotificationResponse> getNotificationsWS(int size,
        SimpMessageHeaderAccessor headerAccessor, Principal principal) throws Exception {
    ActionResult<List<NotificationResponse>> notificationsAr;
    notificationsAr = this.listNotifications(size, principal);
    return notificationsAr.getResult();

}