I don't think GetTimeAsStringResponse is the asyn response bean.
It actually is the response bean
Polling method A polling method returns a typed Response<ResponseBean> that may be polled using methods inherited from Future<T> to determine when the operation has completed and to retrieve the results. See below for further details on ResponseBean.
Callback method A callback method takes an additional final parameter that is an instance of a typed AsyncHandler<ResponseBean> and returns a wildcard Future<?> that may be polled to determine when the operation has completed. The object returned from Future<?>.get() has no standard type. Client code should not attempt to cast the object to any particular type as this will result in non-portable behavior.