Meanwhile, back at the ranch, the original submission was worked on by Shing Wai and others
which lead to yet another JDBCRealm, this one as a putback into the GF v2 trunk.
Please check this latest implementation to be sure it does what you need;
you can read about it in Shing Wai's Blog.
Note that one of the differences between the two implementations is that Edson's was designed to
use exactly the same
configuration as Tomcat's while Shing Wai's does not.
You can provide feedback at Shing Wai's blog or in this thread in the
USERS mailing list.
This feature should show in the next GF v2 build (b07).