Sun Java System Application Server Platform Edition 8.2 Developer's Guide

Access to Shared Frameworks

When J2EE applications and modules use shared framework classes (such as utility classes and libraries) the classes can be put in the path for the System Classloader or the Common Classloader rather than in an application or module. If you assemble a large, shared library into every module that uses it, the result is a huge file that takes too long to register with the server. In addition, several versions of the same class could exist in different classloaders, which is a waste of resources. For more information, see Circumventing Classloader Isolation.