Doubt Regarding the Session

[ChakraPani Margani]

Hi Friends,

I have a problem in the session management.

I need to maintain the login user-id in my application...
For each database interaction I need to send the user-id..
I am maintaining the user-id and other info in a bean and I put that bean in a session variable..

But some times the session will automatically closed and gives nullPointerException when I try to call the session variable.

ex:bean.getUserId();

I am also trying to give the session max age in the web.xml
<session-config>
<session-timeout>0</session-timeout>
</session-config>

But this is also not solve my problem..

Right now i am using RAD to develop my application...
When i run my application in the local system this session problem expires.

please give my any suggestion to solve the problem..

Regards,
ChakraPani.M