This is slightly OT:
How do I get JPA 2.0 functionality to Tomcat 6 or 7? I'm especially interested in the @MapsId annotation and the possibility to mark FK associations with @Id.
Is there a new version of Embedded JBoss supporting the JavaEE 6 classes?
The only solution right now is to download and install a JavaEE 6-compliant web server like JBoss AS 6...
I can't speak here on enabling Tomcat w/ JPA; that's best left to Tomcat forums or other JPA providers like Hibernate/TopLink.
However the latest releases of JBossAS do run in Embedded mode, and fully support JPA2, and are available now.