I am not aware of weblogic security configuration but I guess that start point for should be get through documentation about JAAS and how to write custom login modules.
By very brief look at google I found something about weblogic security:
http://download.oracle.com/docs/cd/E15051_01/wls/docs103/security/fat_client.html
Perhaps it is not exactly what you are looking for ...
I could not find any information how to configure data base security realm on Weblogic.