Serializer ate my DOCTYPE?

[Angus McIntyre]

I've just converted an app I'm writing from using a simple 
transformer (as in the UseStylesheetPI example) to using a chain of 
transformers (as in the Pipe example). Everything works fine, except 
for one small problem: the DOCTYPE (as specified in the <xsl:output/> 
element no longer seems to get written out.

Here, trimmed to a minimum, is the relevant code:
        StreamSource xmlSource = new StreamSource(sourcefile);
        xmlSource.setSystemId(sourcefile);
        Source stylesheet =
        tfactory.getAssociatedStylesheet(xmlSource, media, title, charset);
        TransformerHandler mainhandler =
                saxtfactory.newTransformerHandler(stylesheet);
        XMLReader reader = XMLReaderFactory.createXMLReader();
        reader.setContentHandler(mainhandler);
        reader.setProperty("http://xml.org/sax/properties/lexical-handler";,
                           mainhandler);
        Serializer serializer = SerializerFactory.getSerializer
                (OutputProperties.getDefaultMethodProperties("html"));
        serializer.setOutputStream(new FileOutputStream(targetfile));
        mainhandler.setResult(new SAXResult(serializer.asContentHandler()));
Can anyone suggest what needs to be added to get my DOCTYPE back 
again? (I'd also like to choose the serializer based on the 
<xsl:output/>, but that's a refinement I can add later).

Thanks in advance
Angus
--
[EMAIL PROTECTED]                             http://pobox.com/~angus