Last week I tried to deploy an JSF application, that used to run under Tomcat, to a JBoss 4.0.4 server. I didn't expect any problems, but like most of the times I was too optimistic. The first thing I ran into was the following exception:
java.lang.NullPointerException at javax.faces.webapp.FacesServlet.init(FacesServlet.java:144)
After some searching I found that JBoss comes with MyFaces, while my application contained the RI jars. This seemed to be the problem so I removed them from the lib directory. The app deployed without errors, but no action mehods were called after submitting a form. The forms just submitted without ever reaching backing beans. No exceptions, no warnings, just a dead page.
After some more inspection I found that when putting the MyFaces jars in the lib directory of the application, evertything worked without problem again. After all not that strange, but it would be so much easier with some decent error messages.