String id = h.getId();
String id = h.getClientSessionId();
   public void addListener(InvokerCallbackHandler callbackHandler)   {      log.debug("adding callback handler: " + callbackHandler);      if (callbackHandler instanceof ServerInvokerCallbackHandler)      {         ServerInvokerCallbackHandler h = (ServerInvokerCallbackHandler)callbackHandler;         String id = h.getId();         synchronized(callbackHandlers)         {            if (callbackHandlers.containsKey(id))            {               String msg = "The remoting client " + id + " already has a callback handler";               log.error(msg);               throw new RuntimeException(msg);            }            callbackHandlers.put(id, h);         }      }      else      {         throw new RuntimeException("Do not know how to use callback handler " + callbackHandler);      }   }