Web tier: servlets, JSP, Web frameworks: Sending incremental data to browser with session expiration

  1. There is an operation which is going to take long time in the backend (longer than HttpSession expiration time). So we need to send the data back incrementally to the user screen (browser) so that the session doesn't expire.
    How can we do this?
  2. The conventional way to achieve this (we used this in previous project) would be to have the client refresh every few seconds and show the progress. Even if the backend process takes too long it could possibly indicate the progress to the front end via a database. There are newer ways to achieve this using AJAX I presume.