Wikipedia
Restlet
Restlet is a lightweight, comprehensive, open source RESTful web API framework for the Java platform. Restlet is suitable for both server and client Web applications. It supports major Internet transport, data format, and service description standards like HTTP and HTTPS, SMTP, XML, JSON, Atom, and WADL. A GWT port of the client-side library is also available as well as other editions for Android, OSGi and Google App Engine.