Question: I know glassfish can authenticate against an LDAP server, I also know it can authenticate against my own database. What I would like to do is authenticate users against LDAP, but get their roles from my own database.

Where would I start learning how to create my own custom authentication module?

Answer: 
[HERE](http://x-techteam.blogspot.com/2008/03/glassfish-login-module-simple-example.html) is the step-by-step instructions of how to do this.
See the [Glassfish security FAQ](https://glassfish.dev.java.net/javaee5/security/faq.html), specifically "How do I write/configure my own login module and plug it into GlassFish?"

and [this sun document](http://developers.sun.com/appserver/reference/techart/as8_authentication/)