Access to components within applications and modules installed on the server occurs within the context of isolated class loader universes, each of which has its own EJB, Web, and JSP Engine classloaders.
Application Universe: Each J2EE application has its own class loader universe, which loads the classes in all the modules in the application.
Individually Deployed Module Universe: Each individually deployed EJB JAR, web WAR, or lifecycle module has its own class loader universe, which loads the classes in the module.
A resource such as a file that is accessed by a servlet, JSP, or EJB component must be in a directory pointed to by the class loader’s classpath. For example, the web class loader’s classpath includes these directories:
If a servlet accesses a resource, it must be in one of these directories or it is not loaded.
In iPlanet Application Server 6.x, individually deployed modules shared the same class loader. In subsequent Application Server versions, each individually deployed module has its own class loader universe.