public Object invoke(Invocation mi) throws Exception 
{
      validateArguments(mi);
      Object obj = getNext().invoke(mi);
      return validateReturnValue(mi, obj);
}

 public Object invokeHome(Invocation mi) throws Exception 
{
      validateArguments(mi);
      Object obj = getNext().invokeHome(mi);
      return validateReturnValue(mi, obj);
}

 protected  void validateArguments(Invocation mi) 
{
      if (mi.getType() == InvocationType.REMOTE)
      {
         Object[] params = mi.getArguments();
         for (int i = 0; i <  params.length; i++)
         {
            Object obj = params[i];
            if (obj instanceof TimerHandle)
               throw new IllegalArgumentException("Cannot pass TimerHandle through remote interface");
         }
      }
}

Do some validation of the incoming parameters

 protected Object validateReturnValue(Invocation mi,
    Object retValue) 
{
      if (mi.getType() == InvocationType.REMOTE)
      {
         if (retValue instanceof TimerHandle)
            throw new IllegalArgumentException("Cannot return TimerHandle from remote interface");
      }
      return retValue;
}

Do some validation of the return value