code: private static XPathExpression buildExpression(String xPathExpression, NamespaceContext nsContext)
              throws XPathExpressionException {
          XPath xpath = createXPathFactory().newXPath();
          
          if (nsContext != null) {
              xpath.setNamespaceContext(nsContext);
          }
  
          return xpath.compile(xPathExpression);
      }
docs: Construct a xPath expression instance with given expression string and namespace context.
  If namespace context is not specified a default context is built from the XML node
  that is evaluated against.
  @param xPathExpression
  @param nsContext
  @return
  @throws XPathExpressionException