title: How would you implement an RSS feed in a Java web environment?
body: <p>I am working on an implementation for RSS feeds for a collaboration platform.
  Say there are several thousands of different collaboration rooms where users can share information, and each needs to publish an RSS feed with news, changes, etc...</p>
  
  <p>Using a plain servlet (i.e. <a href="http://www.site.com/RSSServlet/?id=roomID" rel="nofollow noreferrer">http://www.site.com/RSSServlet/?id=roomID</a>) is costly, every time an RSS client is calling the servlet (and this will happen say every 10 minutes for each user registered to an RSS feed on one of the thousand of rooms) this will trigger the entire servlet lifecycle, which is costly.</p>
  
  <p>On the other hand, keeping a static XML file on the disk for each of the thousands of rooms is costly as well, in terms of hard disk space as well as IO operations...</p>
  
  <p>One more limitation - using already existing frameworks might not be an option...</p>
  
  <p>So, how would you implement RSS feeds in a Java envoronment?</p>