Hi Archana,
Ur question, "How do we handle or avoid duplicate requests"
seems to be very weird. I wasn't able to understand 
exactly what u wanted to accomplish !!

Tell me, if u want to avoid duplicate requests, why at all
are u designing the application in servlets ??

I think servlets were made to allow internet programming
and, on the internet, there will always be multiple users
using ur site !!

However, if u meant that u do not want multiple users
to access the same resources on ur site, then the only 
way 2 accomplish that is by using cookies and session
 variables. U can provide a login page, and then for each
user who logs into ur site, u can provide a unique session
id.

Hope this helps !!

Keep me posted.

Cheers !!

Sherbir.