Use output of XSL transformation as new XSL stylesheet

[barney.b]

Hi,

I'm trying to pre-process an XSL stylesheet with another stylesheet,
before using the result to transform an XML document. i.e.:

stylesheet(xsl) --> preprocessor(xs l) --> temp(xsl)
input(xml) --> temp(xsl) --> output(xml)

but I'm getting a NullPointerExce ption. I'm not 100% sure exactly what
is going on here, so if someone could help I'd be grateful.

I've been working from the examples from Sun and Apache Xalan, and so
far have the following:

File input = new File("input.xml ");
File stylesheet = new File("styleshee t.xsl");
File preprocessor = new File("preproces s.xsl");

SAXTransformerF actory stf =
(SAXTransformer Factory)Transfo rmerFactory.new Instance();

// parse preprocessor stylesheet into templates handler
TemplatesHandle r tmpltHand = stf.newTemplate sHandler();
XMLReader reader = XMLReaderFactor y.createXMLRead er();
reader.setConte ntHandler(tmplt Hand);
reader.parse(ne w InputSource(new FileInputStream (preprocessor)) );

// create transformer handler based on templates handler
Templates templates = tmpltHand.getTe mplates();
TransformerHand ler transHand =
stf.newTransfor merHandler(temp lates);

// parse page stylesheet through proprocessor
reader.setConte ntHandler(trans Hand);
reader.setPrope rty("http://xml.org/sax/properties/lexical-handler",
transHand);

transHand.setRe sult(new StreamResult(Sy stem.out));
reader.parse(ne w InputSource(new FileInputStream (stylesheet)));

This all works fine, and displays the modified stylesheet. It's when I
try to use this stylesheet it all goes wrong. I thought I could just
redirect the output of the last stage, via a SAXResult. into a new
TemplatesConten tHandler, and then use this to transform the actual
input.

replace:
transHand.setRe sult(new StreamResult(Sy stem.out));

with:
TemplatesHandle r tmpltHand2 = stf.newTemplate sHandler();
transHand.setRe sult(new SAXResult(tmplt Hand2));

However, when I run this I get a NullPointerExce ption in
TransformerHand lerImpl.endDocu ment.

Can anybody see what is wrong here, or suggest a better way of doing
this?

Cheers,

Barney