I should have mentioned: I realize that DefaultDS is used for other things in Jboss. The only reason I removed it temporarily was to easily illustrate through an exception that DefaultDS is trying to be used by a PAR that doesn't even reference DefaultDS, but a different datasource entirely.
I found the solution, although I don't see it alluded to in the documentation or examples anywhere. I have to duplicate the JNDI name of the datasource twice in persistence.xml:
Previously I only specified <jta-datasource> thinking that would be sufficient.
Crap, that was supposed to post as:
Nevermind, this I tried disabling HTML but this still doesn't post correctly, so I'll spell it out. You have to also specifiy the custom property hibernate.connection.datasource to the exact same string as jta-datasource. This is the only way I found to not have hibernate use DefaultDS.
Do a favor for me:
Find the %JBOSS_HOME%/server/myconfig/deploy/ejb3.deployer/META-INF/persistence.properties and comment the datasource line
and the dialect one
Does it works?