Most GOOD documentation is always restricted information inside companies.
Check out the Apache project, I think there's documentation for Tomcat and/or other of their projects online. If the docs are as good as (most of) their software they're OK.

Have you read "J2EE design and development" by Rod Johnson? It's IMO required reading for anyone involved in desiging a J2EE system.

Thanks jwenting but is it possible to have some documentations of student projects of some universities?? If yes how can I get them..

Ask them...
There may be sites where people can post their stuff for others to submit as their own (homework cheating...) but I wouldn't know where to find them and wouldn't mention them if I did as I frown upon such practices.

hehe ... you're right ... but I'm not the kind of a guy who just copies stuff around .... I like to get into depth of something and then start working. But I want some initial boost ... I've done some initial working ... but I want it more precise to professional ... thats why I asked for the docs.