docs: protected DocumentBuilder getDocumentBuilder() throws ServletException {
          DocumentBuilder documentBuilder = null;
          DocumentBuilderFactory documentBuilderFactory = null;
          try {
              documentBuilderFactory = DocumentBuilderFactory.newInstance();
              documentBuilderFactory.setNamespaceAware(true);
              documentBuilder = documentBuilderFactory.newDocumentBuilder();
          } catch (ParserConfigurationException e) {
              throw new ServletException("jaxp failed");
          }
          return documentBuilder;
      }