Apache Wink is a simple yet solid framework for building RESTful Web services. It is comprised of a Server module and a Client module for developing and consuming RESTful Web services.
The Wink Server module is a complete implementation of the JAX-RS v1.0 specification. On top of this implementation, the Wink Server module provides a set of additional features that were designed to facilitate the development of RESTful Web services.
The Wink Client module is a Java based framework that provides functionality for communicating with RESTful Web services. The framework is built on top of the JDK HttpURLConnection and adds essential features that facilitate the development of such client applications.
XINS is an open-source Web Services framework supporting HTTP protocols such as REST, SOAP, XML-RPC, JSON, JSON-RPC and more.
From the specifications written in simple XML, XINS generates the Client API (.jar), the Java server code template (.war), the WSDL and the documentation of the specification in HTML (with the test forms) or in OpenDocument format.
Jersey is the open source (under dual CDDL+GPL license), production quality, JAX-RS (JSR 311) Reference Implementation for building RESTful Web services. But, it is also more than the Reference Implementation. Jersey provides an API so that developers may extend Jersey to suite their needs. The governance policy is the same as the GlassFish project.