Java doesn't support JARs inside JARs by itself.
You can have JAR files inside a WAR (in the WEB-INF/lib directory). The web container has a special classloader that will look for the JARs in the WEB-INF/lib directory inside a WAR.
But the normal Java launcher (used to run stand-alone Java apps) does not have any mechanism to look for classes in a JAR inside another JAR.
If you really want this you can write your own ClassLoader that supports this, but that's not so easy to do.
[ March 06, 2007: Message edited by: Jesper Young ]