docs: private void returnToInvalidForm(
              final ActionRequest req,
              final ActionResponse res,
              final String name,
              final Map<String, String> attributes,
              final Set<String> invalidFields,
              final String actionParameter) {
  
          /*
           * JSP/JSTL/EL is not good at collection.contains();  Convert the
           * invalidFields to a format that's easy to read in the JSP.
           */
          final Map<String, Object> invalidFieldsMap = new HashMap<>();
          for (String fieldName : invalidFields) {
              invalidFieldsMap.put(fieldName, Boolean.TRUE);
          }
  
          // Need to store some items to display invalid fields;  would be
          // handy to have support for javax.portlet.actionScopedRequestAttributes
          final PortletSession session = req.getPortletSession();
          session.setAttribute(INVALID_FIELDS, invalidFieldsMap);
          final Map<String, String> previousResponses = new HashMap<>();
          previousResponses.put("name", name);
          previousResponses.putAll(attributes);
          session.setAttribute(PREVIOUS_RESPONSES, previousResponses);
  
          // Send the user to the report screen
          res.setRenderParameter("action", actionParameter);
      }