Depends on the vendor, and in some cases there are tools that prepare
the files for you.

To try and answer the question ... in JBoss, for example there is a
jboss.xml and ejb-jar.xml at the very least, for just an ejb jar (no
ear) . If you have an ear, you also get an application.xml . For every
WAR you have in an EAR (not mandatory) , you also get a web.xml . If
you use struts, hibernate, or spring, you get even more ;-).

Note that annotations have helped this situation, before java 5.0 with
xdoclet and I believe the upcomming ejb 3.0 .

HTH,
Robert