Limit on users accessing web-application simultaneously

My web-application's requirement is at any given time only one user should be allowed to access the application. How can I do this in JSP? Got suggestions from my colleagues here that we can use App Scope variables.. Pls help me on this...

Thanks in advance...

Project Environment -- Tomcat 5.0, Java 1.4.2

NOTE:: STRUTS and EJB NOT USED

[363 byte] By [Wowa] at [2007-11-27 0:27:07]