How do i setup Login module in my web application? in Java?

I am making web application in java. My username and passwords as well as roles are stored in database. I could use jdbcRealm, but it forces me to use a specific structure which i dont have in my project. So, how do i do it? I am u开发者_运维百科sing Glassfish v3.0 with Netbeans 6.8. I read few tutorials about custom LoginModule but i am not getting anything out of it. How do you all people do it practically in your projects? If you can show me code of custom LoginModule then also it will do.

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Spring Security is what you're looking for.