Tomcat: how to admin users / group / roles into SQL database ??

Hi - I am building a user-group-role database on SQL server, and using Tomcat JDBCRealm to authenticate user logins to my webapp against this database (easy to set up - works well).
I would now also like to use the Tomcat admin client (in V4.1 and V5) to create and edit the users / groups / roles stored in this SQL server database - ie. to replace the tomcat-users.xml file which is managed by the admin client using a MemoryUserDatabase.
Has anyone tried anything like this, if so ...
1. Are there any "JDBC" or "SQL" UserDatabase classes I can use to do this (rather than MemoryUserDatabase).
2. If not, and I wrote my own implementation, what else would I need to configure to plug it into Tomcat ?

Thanks for any feedback ...

I hardly ever look at the admin application, but wouldn't it just involve switching its web.xml file to use a JDBCRealm instead of a MemoryRealm ?

No coding required! Use JDBCRealm classes that Tomcat gives you, and that you've already used for your own application.