jersey-project
· Jersey is the open source (under dual CDDL+GPL license) JAX-RS (JSR 311)
production quality Reference Implementation for building
RESTful Web services.
Download JD-GUI to open JAR file and explore Java source code file (.class .java)
Click menu "File → Open File..." or just drag-and-drop the JAR file in the JD-GUI window jersey-project-1.19.4.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.