GWT and async requests (startAsync)

[rjcarr]

I've had a long-poll implementation using gwt for a long time now. It defers the response until either an update or a timeout occurs. It works well, but it uses both a socket (inexpensive) and a thread (expensive), so I'd like this to use the async requests introduced in servlets 3.0. I've used async requests in non-gwt servlets and it's worked well.

In GWT however, once I've deferred the response, I can't figure out how to serialize the the response object once it's ready. For example, say I have this gwt-rpc method:

    public String longpoll()

Once inside I can defer the response with:

    getThreadLocalRequest().startAsync();


But once I'm ready to complete the response how is that String response serialized and returned (since I am no longer in the scope of the longpoll method)? (Note that the String response is just an example, in my case it's actually a custom object.)

Looking at the API for RemoteServiceServlet I don't see anything useful, except the onAfterResponseSerialized(String) which I can probably figure out how it works to come up with my own serialization, but this seems dangerous.

I think more generally my question is: is there any way to manually serialize an object and send it out with the response object?  I think if I knew that then it would solve all my problems.  

Thanks!

[Thomas Broyer]

GWT RPC has been thought of as blocking on the server side. Making it async would require changes to the RemoteServiceServlet: most likely the method would be async just like on the client side with the implementation calling the callbacks onSuccess or onFailure.

Your best bet here would be to write a RemoteServiceAsyncServlet by copying from RemoteServiceServlet, hoping for all underlying APIs to be public.
Either that or move off of RPC for that call (future proof)

[Robert J. Carr]

Thanks Thomas. I was hoping it'd be easier and I was just missing something. Moving this call out of rpc is probably the best solution. Thanks again for the guidance!

Since servlets 3 had been out for a long time now it'd be a great idea to have the developers write this feature into RemoteServiceServlet. 

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