Entry level help needed

[Hao Jiang]

Hi there,
I am a new Tomcat user. Currently I am using Tomcat 5.
My question is this. If I want to develop a servlet of my own which handles 
user management in basic authentication model, such as add user, add role, etc, 
how can I do in my own servlet? For example, should I get a tomcat server 
instance? 
 
thank you very much,
Hao