code: private void addDatasourceIfNeeded(ServletRequest req)
              throws JspException
      {
          if (_match == null)
              return;
  
          for (int i = 0; i < _match.length; i++) {
              if (!_optionList.contains(_match[i])) {
                  if (!_match[i].equals(NULL_VALUE))
                      addOption(req, _match[i], _match[i]);
              }
          }
      }
docs: add dthe datasource values if needed.