code: private static String xpath( final String xml, final XPathExpression xpath )
              throws ParserConfigurationException, SAXException, IOException, XPathExpressionException {
          final DocumentBuilder builder = DOCUMENT_BUILDER_FACTORY.newDocumentBuilder();
          final Document doc = builder.parse(new ByteArrayInputStream(xml.getBytes()));
          return xpath.evaluate(doc);
      }
docs: Extract the desired identifier value from an XML response using XPath