Long running servlet

Question

I wrote a servlet for Tomcat to do update a DB table at 5 minutes interval for about 1.5 hours. I use a parm to control its start and stop. The 5 minutes interval is controlled by Thread.sleep(300000L);. Although I only need one instance of this servlet, I use some static variables in the servlet so that even if new instance is init by Tomcat due to whatever reason the process will continue. But I encountered problems.
First of all, I don't know if servlet should be used for such purpose, or there is other better/right way to do this within Tomcat. Secondly, my servlet works sometimes but failed mostly. It usually failed with NullPointerException on some static variable. Not sure if "static" has anything to do with it but from all my failed run they stopped at static variables. Hope somebody can point me to the right direction.

Answer 1

I would recommend that you look at [Quartz Scheduler|http://www.quartz-scheduler.org/docs/index.html] for your job scheduling.
As far as the NullPointerException goes, we need to see your code and the stack trace of the error to be able to help you with that...