Comment by larse...@gmail.com: If you don't include a jsr-303 validator, then you'll get this WARNING.
If you want it to go away, you can include the hibernate validator of versions greater than or equal to 4. I'm unaware of any other 303 bean validators out there.
Or you could just swallow the WARNING aswell. For more information: http://code.google.com/p/google-web-toolkit/wiki/RequestFactoryInterfaceValidation -- http://groups.google.com/group/Google-Web-Toolkit-Contributors
