@Override
 public void messageReceived(T request, TransportChannel channel) throws Exception {
   synchronized (InterceptingTransportService.this) {
     if (actions.contains(action)) {
       List<TransportRequest> requestList = requests.get(action);
       if (requestList == null) {
         requestList = new ArrayList<>();
         requestList.add(request);
         requests.put(action, requestList);
       } else {
         requestList.add(request);
       }
     }
   }
   requestHandler.messageReceived(request, channel);
 }