Question

I wish to run a function for every user with a session at regular intervals that will check if a user is active. If not active, the function will remove the user from the list of users in the servlet context and clear the user session.

What can I use that will run the function at regular timed intervals for each user?

From what I understand, servletcontextlistener runs only once for the life of the servlet and not for each user so it’s not usable. Also, that using threads is advised against in a servlet.

Edit:
Users (using ajax) call a action which contains function that updates a variable I’ve stored for each user that indicates the last time they contacted the server.

Answer 1

You are probably looking for javax.servlet.http.HttpSessionListener.
Create one, register it in web.xml and have the sessionDestroyed do your work.