/**
    * Render a source XML file to a PDF layout using FOP and Xalan.
    *
    * @param xml the source XML Stream.
    * @param xsltStream the xslt file stream to be used for XML to XSL-FO.
    * @param out the Output Stream where FOP will write.
    *
    */
   public void renderXMLtoPDF(StreamSource xml, StreamSource xsltStream, OutputStream out)
   {
      try
      {
         // configure fopFactory as desired
         fopFactory = getFopfactory();
         // configure foUserAgent as desired
         FOUserAgent foUserAgent = fopFactory.newFOUserAgent();
         // Start XSLT transformation and FOP processing
         // Construct fop with desired output format
         Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, foUserAgent, out);
         // Setup XSLT
         TransformerFactory factory = TransformerFactory.newInstance();
         Transformer transformer = factory.newTransformer(xsltStream);
         // Set the value of a <param> in the stylesheet
         transformer.setParameter("versionParam", "2.0");
         // Resulting SAX events (the generated FO) must be piped through
         // to FOP
         Result res = new SAXResult(fop.getDefaultHandler());
         // Start XSLT transformation and FOP processing
         transformer.transform(xml, res);
      }
      catch (FOPException e)
      {
         logger.error("SAX Error detected during PDF creation", e);
      }
      catch (TransformerException ex)
      {
         logger.error("Transformer Error detected during PDF creation", ex);
      }
   }