code: public InputSource resolveEntity(String publicId, String systemId)
            throws org.xml.sax.SAXException
    {
      return getCurrentProcessor().resolveEntity(this, publicId, systemId);
    }
docs: Resolve an external entity.
  
  @param publicId The public identifer, or null if none is
  available.
  @param systemId The system identifier provided in the XML
  document.
  @return The new input source, or null to require the
  default behaviour.
  
  @throws org.xml.sax.SAXException if the entity can not be resolved.