title: ServletRequestListener - Getting the userprincipal returns null
body: <p>I'm having a web-application that is secured with HTTP-Basic auth. 
  I also implemented a filter using the <code>ServletRequestListener</code> interface. Now when the filter calls the <code>requestInitialized</code> method, the getUserPrincipal-Method of the request returns null. But when I check the request headers, the authorization-header is set with the encrypted value. Here's the code:</p>
  
  <pre class="lang-java prettyprint-override"><code>@Override
  public void requestInitialized(ServletRequestEvent e) {
  
    HttpServletRequest request = (HttpServletRequest) e.getServletRequest();
  
    //p is null
    Principal p = request.getUserPrincipal();
  
    Enumeration&lt;String&gt; enH = request.getHeaders("Authorization");
    while (enH.hasMoreElements()) {
      String s = enH.nextElement();
      System.out.println(s);
      //prints. 
      //Basic c3RhY2tvdmVyZmxvdzpteXBhc3N3b3Jk
    }
  }
  </code></pre>
  
  <p>Why is the userprincipal not initialized?</p>