[xsl] Xalan, errors and ErrorListener

Subject: [xsl] Xalan, errors and ErrorListener
From: Mike Brown <mike@xxxxxxxx>
Date: Thu, 9 Aug 2001 14:12:32 -0600 (MDT)
I'm using Xalan 2.2.D6, trying to use my own ErrorListener to nicely format problems 
encountered during stylesheet preparation. I register an instance of the ErrorListener 
implementation with the TransformerFactory, and then I call the factory's newTemplates
method to get the prepared stylesheet. 

My stylesheet intentionally contains a bad attribute name in an <xsl:template> start tag,
causing the ErrorListener's error method to be invoked.

Both my error and fatalError methods prepare a formatted String using info in the
TransformerException that is passed into them, and then they throw a new
TransformerException that contains only this String as its message.

Apparently this isn't a very good way to go about it because Xalan's StylesheetHandler
class catches this new TransformerException, wraps it in a SAXException, which gets
thrown and makes its way up to the TransformerFactoryImpl which blindly takes it as a
random parsing error. It then gets wrapped in a new TransformerException, which is passed
to the ErrorListener's fatalError method. 

I tried to look at TransformerFactoryImpl and StylesheetHandler but couldn't figure out
how it avoids an infinite loop of passing the exception back and forth between the
factory's newTemplates method and my fatalError method. Yet somehow we get out of it and
in the end I get a TransformerException with a message saying something along the lines
of "There was a fatal error. Here it is: There was an error. Here it is: (...)".

If Xalan's behavior is reasonable, I don't see how I can easily write my ErrorListener
implementation to distinguish between an error and a fatal error. The fatal error might
actually be a regular error that has already been reported. Is this really the way it 
should work?

   - Mike
____________________________________________________________________________
  mike j. brown, fourthought.com  |  xml/xslt: http://skew.org/xml/
  denver/boulder, colorado, usa   |  personal: http://hyperreal.org/~mike/

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