code: protected void redirectToAuthenticationPage(DataBinder binder) {
          if (_page != null) {
              binder.mul(Service.SERVICE_HTTP_HEADER, String.class, String.class).add("Content-Type", "text/html; charset=utf-8");
              binder.put(Service.SERVICE_PAGE_TARGET, _page + "?_redirect_=" + binder.get(Service.REQUEST_TARGET_PATH));
  //_logger.log(Level.FINE, "redirecting to {0}", binder.get(Service.SERVICE_PAGE_TARGET));
          }
      }
docs: /*#
  Redirects to the configured authentication page, passing the target service as parameter "_redirect_".