code: public static SAXSource newSAXSource(Reader reader, String systemId, JstlEntityResolver entityResolver)
              throws ParserConfigurationException, SAXException {
          SAXSource source = new SAXSource(newXMLReader(entityResolver), new InputSource(reader));
          source.setSystemId(wrapSystemId(systemId));
          return source;
      }
docs: Create a SAXSource from a Reader. Any entities will be resolved using JSTL semantics.
  
  @param reader the source of the XML
  @param systemId the system id
  @param entityResolver for resolving using JSTL semamtics
  @return a new SAXSource
  @throws ParserConfigurationException if there was a configuration problem creating the source
  @throws SAXException if there was a problem creating the source