A J2EE Library is a special add-on for the SAP J2EE Engine. Using a J2EE Library project is easy: Refer to public parts (with purpose assembly) of Java DCs (buildtime dependency) or other J2EE Library DCs (runtime dependency).
An SDA file containing the jar-files from the Java DCs and the deployment descriptors.
J2EE Library DCs are best handled using the J2EE DC Explorer in the J2EE Perspective.