Dave Kuhn has put together a comprehensive guide to piecing together GWT and Spring, a nice recipe for the Java heads among you.

Dave starts out by detailing why you would want to do this, and how it changes the architecture of your application.

He then gets to a tutorial that has you creating the project correctly, and configuring an actual service. Once you are done with the code, you need to setup hosted mode to point to a nice external tom cat via:

-out www GwtWisdom/GwtWisdom.html
-noserver
-port 8080