String stylesheet = "test.xslt" ;

      // load the transformer using JAXP

      TransformerFactory factory ;
      Transformer transformer ;
      DocumentSource source ;
      DocumentResult result;
      Document transformedDoc ;
      XMLWriter writer = null;
      OutputFormat format = null;
      try
      {
        factory = TransformerFactory.newInstance() ;
        transformer = factory.newTransformer(new StreamSource(stylesheet)) ;
        document = this.read("test.xml") ;
        source = new DocumentSource(document) ;
        result = new DocumentResult() ;
        // now lets style the given document
        System.out.println("begin transform xml") ;
        transformer.transform(source, result) ;
        transformedDoc = result.getDocument() ;
        System.out.println("end transform xml") ;
        return transformedDoc;
      }
      catch(TransformerConfigurationException te)
      {
        te.printStackTrace();
        System.out.println("transform xml TransformerConfigurationException") ;
        return null;
      }
      catch(TransformerException te)
      {
        te.printStackTrace();
        System.out.println("transform xml TransformerException") ;
        return null;
      }
本段代码执行后，transformedDoc中没有包含相应的HTML数据（另外用一个函数输出到文件中），为何？