code: public String evaluate(String select, Document document)
          throws XpathException {
          try {
              return engine.evaluate(select, new DOMSource(document));
          } catch (XMLUnitException ex) {
              throw new XpathException(ex.getCause());
          }
      }
docs: Evaluate the result of executing the specified xpath syntax
  <code>select</code> expression on the specified document
  @param select
  @param document
  @return evaluated result
  @throws XpathException