More detail to the problem: I'm using JDK 1.5.0_16.
... Here is the mysql-dq.xml (JBoss DS def) extract: ...
Just to be sure it isn't a typo. Shouldn't this be mysql-ds.xml?
Yes - it was a typo - it must be mysql-ds.xml.
I do not see your code extract on the forum.
Verify that the connector on the session is set to JNDIConnector.STRING_LOOKUP and not COMPOSITE_NAME_LOOKUP which would be the default that worked previosly with OC4J.
you may be experiencing a common configuration issue with application servers that are based on the Catalina (Tomcat) servlet container where the lookupType must be STRING_LOOKUP.
Hibernate may default to STRING_LOOKUP as the lookupType because it normally runs in JBoss which is Catalina based - so it will work out of the box on JBoss.
See the following EclipseLink on JBoss tutorial where we describe configuring the eclipselink.session.customizer so that the lookupType on ideally both JTA and non-JTA datasource connectors are changed from " COMPOSITE_NAME_LOOKUP" to "STRING_LOOKUP".
The following page describes the use of JNDIConnector.STRING_LOOKUP in general for all Catalina based servers.
Also verify that the *-ds.xml config files are setup using the following section as a guide.