I'm developing a Google App Enigne application that uses some REST services and offers in turn web services. I'm using the GAE Eclipse plugin. I have 2 questions:
You can use Jersey 1.5. You can see all frameworks that will play on GAE at http://code.google.com/p/googleappengine/wiki/WillItPlayInJava
But GAE has realized on version 1.7.5 as experimental service Endpoints which in term are rest service. Check https://developers.google.com/appengine/docs/java/endpoints/
For web service I don't know if you mean soap service..JAX-RS is the specification for rest service, instead you should use JAX-WS I don't try the compatibility with this specification.