title: How to do dynamic URL Rewriting in J2EE
body: <p>Back in my ASP.NET days, I used <a href="http://urlrewriter.net/" rel="nofollow noreferrer">URLRewriter.NET</a> to do dynamic URL Rewrites.  Basically, it's an HTTPModule that intercepts page requests and rewrites the URLs according to rules that you define, very similar to MOD_REWRITE.  However, it also lets you define a "Custom Transform," a class with a single method that does URL translations for you on-the-fly.  You can have this method hit the DB, access the Application[] collection, pretty much do anything your heart desires.  </p>
  
  <p>Is there any equivalent to this in the J2EE world?  I want to be able to rewrite URLs dynamically and delegate this rewriting to some Java code.  I do NOT want to just set up a list of static rewrites.  Likewise, it needs to do actual URL masking, and NOT 3XX redirects.  </p>
  
  <p>If there isn't anything out there that does this, how would I go about building this functionality myself?</p>