File APIs for Java Developers
Manipulate DOC, XLS, PPT, PDF and many others from your application.
The moose likes Servlets and the fly likes Concurrent access problem Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login
JavaRanch » Java Forums » Java » Servlets
Bookmark "Concurrent access problem" Watch "Concurrent access problem" New topic

Concurrent access problem


Joined: Sep 27, 2001
Posts: 3
Currently i'm working on Intranet Site which runs on
technologies like JSP,IBM Websphere 3.5 and database
Here main problem occurs when concurrently user
accesses same Module.Then Server sometimes throws
1. Null pointer Exception
2. Number Format Exception
3. ArrayIndex out of Exception

This problem Occurs only when user concurrently
accesses the same module.
When there is no concurrent user then All my modules
works fine.

please let me know the causes....
sachin V.

Sachin Vesanekar

Sachin Vesanekar
Matthew Phillips
Ranch Hand

Joined: Mar 09, 2001
Posts: 2676
Please read and re-register with a name that conforms. We would like you to be able to continue to post here at JavaRanch.

Matthew Phillips
William Brogden
Author and all-around good cowpoke

Joined: Mar 22, 2000
Posts: 13037
It is extremely likely that you have not been paying attention to the Thread safety requirements of coding servlets. Probably there are one or more instance or static variables in your servlet/JSP that are dynamically changed during a request. Tch Tch! Bad Show! Thou shalt not use instance or static variables, only local ("automatic") variables for data that is specific to a particular request.

author of:
I agree. Here's the link:
subject: Concurrent access problem
It's not a secret anymore!