In JBoss 4.0.4.GA it took me awhile to figure out how to enable trace level debugging.
Typically you could do something like this to enable trace level debugging for a category of classes.
However JBoss 4.0.4.GA has an older log4j implementation so you need to use JBoss’s custom TRACE level.
This is documented in the release notes for JBoss-4.2.1.GA.
Since the latest log4j includes a trace level, there is no need to reference the custom jboss TRACE level in conf/jboss-log4j.xml configs, JBAS-4163.