code: protected void configureFactory(DocumentBuilderFactory dbf) {
      dbf.setValidating(true);
      dbf.setIgnoringComments(false);
      dbf.setIgnoringElementContentWhitespace(false);
      dbf.setNamespaceAware(true);
      protectAgainstXxeAttacks(dbf);
    }
docs: allows subclasses to configure the {@link DocumentBuilderFactory}.
  @param dbf the factory to configure