Question

I know what this exception reports for me. Its a null return. But I want to pass a null object, and want to receive a null object. I dont want to check for null and create a empty object, its a waste of cpu resource, since null conveys what it has to, no data found. How can I allow JSON to send a null.

OR

Am I without options here, I need to create a dummy object and send it over the wire ?

SubscriberListRequest request = new

SubscriberListRequest((SubscriberListConcrete)element.getValue()) ;
SubscriberListResponse response ;
clientSession = sessionManager.getClientSession(identityHash) ;
clientSession.getSendQueue().sendRequest(request) ;
try {
    response = (SubscriberListResponse)clientSession.waitAndGetResponse(request) ;
} catch (WaitedLongEnoughException e) {
    return Response.serverError().build() ;
} catch (UnableToResolveResponseException e) {
    return Response.serverError().build() ;
}
//
// Should I check for response.getSubscriberList() == null, create a new SubscriberList() and send it over the wire ?
//
return Response.ok(response.getSubscriberList()).build();

Answer 1

You can’t really pass null over the wire, so I suggest you use the Null Object pattern (http://en.wikipedia.org/wiki/Null_Object_pattern) and create a static empty array/list in SubscriberListResponse which will be returned from SubscriberListResponse.getSubscriberList() in case of no results. Then you don’t have to check for null in your service, but in getSubscriberList to make sure you always return a valid object.