为什么XMLStreamReader / StAXSource会从XML中删除注释？

Question

The code below (based on sample code from http://jax-ws.java.net/nonav/jax-ws-20-fcs/arch/com/sun/xml/ws/util/xml/StAXSource.html )

String xml = "<a><b>a text</b><!--a comment--><b/></a>";
StringReader sr = new StringReader(xml);
XMLStreamReader reader = XMLInputFactory.newInstance().createXMLStreamReader(sr);
Source source = new StAXSource(reader);     
//Source source = new StreamSource(sr);
Result result = new StreamResult(System.out);      
TransformerFactory.newInstance().newTransformer().transform(source, result);

yields the following result:

<?xml version="1.0" encoding="UTF-8"?><a><b>a text</b><b/></a>

ie it strips out the xml comment. If I replace the StAXSource/XMLStreamReader with the StreamSource the comment is preserved.

Does anyone know why the XMLStreamReader/StAXSource combination strips them out and if there is any way to prevent it? The testing was done in 1.6 and 1.7 environments with no third party jars, so the XMLStreamReader becomes a

com.sun.org.apache.xerces.internal.impl.XMLStreamReaderImpl 

Thanks

Answer 1

EDIT: Just tried as described here ie

case XMLStreamConstants.COMMENT:
  System.out.print("<!--");
  if (xmlr.hasText())
     System.out.print(xmlr.getText());
...

and it DOES read the comments. This does not answer the original question yet though ...