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RE: Fast text output from SAX?

• To: "Michael Kay" <michael.h.kay@n...>
• Subject: RE: Fast text output from SAX?
• From: "Andrew Welch" <AWelch@p...>
• Date: Wed, 14 Apr 2004 08:38:10 +0100
• Cc: "XML DEV" <xml-dev@l...>
• Thread-index: AcQhNHVdtrsqnLDMQw2YDWAg91kTyAADHqJgAAW7IUAAARHCkAADP51gACHzG6A=
• Thread-topic: Fast text output from SAX?

> > I've often had the requirement to alter/add to the xml as it passed 
> > through a set of SAXFilters.  I've always been under the impression 
> > that to write out the xml at the end of the filter chain I either
> > needed to:
> > 
> > A) use DM's XMLWriter or similar
> > 
> > or
> > 
> > B) use a SAXTransformerFactory which allowed me to use 
> setResult() to 
> > give it a Writer.
> > 
> > Other than that I thought the SAX events were 'lost' by the 
> handler, 
> > which I've always considered odd.  For me, the handler 
> should have the 
> > ability to write out the xml inbuilt into it, without the need for 
> > XMLWriter or SAXTransformerFactory.
> 
> I'm confused. What do you mean by "the handler"?

The ContentHandler, DefaultHandler, or in this case the
TransformerHandler.

> > 
> > Reading here,
> > 
> > http://java.sun.com/j2se/1.4.2/docs/api/javax/xml/transform/sa
> > x/SAXTrans
> > formerFactory.html#newTransformerHandler()
> > 
> > you can see how I made my assumption.
> 
> Sorry, I don't understand what assumption you made, let alone 
> how you made it!


My assumption was that a call to newTransformerHandler() with no
arguments (ie no stylesheet) would return a TransformerHandler created
from the identity stylesheet.  Where a stylesheet is specified, a
transform must take place and so a tree needs to be created for the
source - which incurs all the usual costs of building the tree.  I
assumed that these costs were still involved when using the zero
argument newTransformerHandler().

If these costs aren't involed, then this is surely the best way for the
orginal poster to go from a stream of sax events to xml text.



> > How does Saxon go from
> > sax events to a Result using an empty TransformerHandler()?
> 
> The IdentityTransformerHandler gets SAX events in 
> (originating typically from a DOMSource, a SAXSource, or a 
> StreamSource), and passes them straight through to an output 
> method associated with a DOMResult, SAXResult, or 
> StreamResult. It's a dozen lines of code.


Ok.

> > Is there anything like
> > the performance costs of building a tree for the source and
> > performing a transform?  
> > 
> No.

Excellent.  Although it's a bit of a misnomer calling it a 'transformer
handler' :)


cheers
andrew

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