public void valueUnbound(HttpSessionBindingEvent event) {
      if (log.isDebugEnabled()) log.debug("Logout " + _jUserName);

      if (_realm instanceof SSORealm) ((SSORealm) _realm).clearSingleSignOn(_jUserName);

      if (_realm != null && _userPrincipal != null) _realm.logout(_userPrincipal);
    }