Improving performance in distributed Web applications

* Keep the session minimal - generally a bad idea to store shared objects in the session.
* Don't bypass setAttribute - if you just call getAttribute() to retrieve the Vector and then add something to it without then calling setAttribute again, the container might not realize that Vector has been changed.
* Use fine-grained session attributes - finer-grained objects in the session rather than one big monolithic object.
* Invalidate when done - call HttpSession.invalidate()
* Keep the session clean - remove reference to unuse thing to help GC

http://www-106.ibm.com/developerworks/library/j-jtp07294.html