code: public User loadUser (HttpServletRequest req)
          throws PersistenceException
      {
          String authcook = CookieUtil.getCookieValue(req, _userAuthCookie);
          if (USERMGR_DEBUG) {
              log.info("Loading user by cookie", _userAuthCookie, authcook);
          }
          return loadUser(authcook);
      }
docs: Fetches the necessary authentication information from the http request and loads the user
  identified by that information.
  
  @return the user associated with the request or null if no user was associated with the
  request or if the authentication information is bogus.