using GWT RPC mechanism with my customized Servlet

Question

I currently have a GWT application which uses the RequestBuilde to send messages to a servlet I have (using POST and GET), and my servlet (in doPost and doGet) "pauses" the request (this is done by using Servlets 3.0 spec) and adds it to a queue.
Additionally I have a Daemon thread which runs in the background and "plays" the request when there is new data.
This works great for me apart from the fact that I'm just sending strings for now and I'd like to utilize the RPC mechanism to send Objects.
My question is this:
If I create my myServiceImpl class which extends RemoteServiceServlet how should I handle the doPost and doGet if at all?
I need to pause my request to utilize the asynchronous support, where should this be accomplished? I though maybe to call this.getThreadLocalRequest() method in my RPC method in myServiceImpl class but I'm not sure how wise that will be.
I'm not sure I even understand how GWT handles the call from the client side of that asynchronous interface. Does it by any chance call the doGet for example of the servlet and makes sure it calls the required RPC method?
I'm sorry if I made a mess of things it's just that I can't find more detailed technical information as exactly how this RPC business works.
Appreciate any lending hand
Ittai

Answer 1

To understand RPC forget about POST and GET it works differently (that is from a programming perspective. Internally it does use it, but you don't see or need to understand it, unless you want to do something exotic). A good starting point is on RPC is the GWT docs: http://code.google.com/webtoolkit/tutorials/1.6/RPC.html

To give you a summary. When using RPC your servlet myServiceImpl needs to implement the methods of an interface named myService, besides extending the RemoveServiceServlet. The methods get as arguments the data you want to send to the server.

Next to the myService interface you need to create an myServiceAsync interface (both interface's should be in a client subpackage). This myServiceAsync inteface should contain the same methods as the myService interface except each method returns void and has an additional last argument AsyncCallback callback.

In you client you need to instrument GWT to generate the RPC via GWT.create (see the documentation for the details.

To use RPC, call the methods on the myServiceAsync interface in your client code and GWT takes care of sending it to the servlet. The servlet will then call the matching method with the arguments you passed on the client. This is done asynchronous. Thus the client return directly from the call.

When the server sends the result back the callback you passed myServiceAsync is used or OnError or OnSuccess is called. OnError if the method on the server side threw an error, else OnSuccess. The OnSuccess will have as argument the return value from what you returned in the method implemented by your servlet.