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RE: JAXP and SAX ErrorHandler stuff

• From: Dylan Walsh <Dylan.Walsh@K...>
• To: xml-dev@l...
• Date: Fri, 04 May 2001 14:16:38 +0100

I have not read your email in detail, but can you not call the
getParser() method, which returns the underlying org.xml.sax.Parser, on
which you can then call setErrorHandler()?
I have never used SAX, but figured that out from reading the JavaDocs.

> -----Original Message-----
> From:	Mike Brown [SMTP:mike@s...]
> Sent:	Friday, May 04, 2001 2:07 AM
> To:	xml-dev@l...
> Subject:	JAXP and SAX ErrorHandler stuff
> 
> I feel like I'm really just not grasping something here.
> 
> The javax.xml.parsers abstract classes seem to exist for the purpose
> of
> making it so that I can code for them instead of for specific parsers.
> 
> Quoting from the ErrorHandler API docs, "WARNING: If an application
> does
> not register an ErrorHandler, XML parsing errors will go unreported
> and
> bizarre behaviour may result. For XML processing errors, a SAX driver 
> must use this interface instead of throwing an exception."
> 
> I would think that registering an ErrorHandler is something that is so
> essential to any SAX parsing operation that it would be a part of the
> JAXP classes. So I don't understand why a setErrorHandler method is
> not
> in the JAXP SAXParser abstract class.
> 
> I want to have my ErrorHandler output to a particular Writer, so my 
> approach has been the following (try/catch notwithstanding):
> 
>   import java.io.*;
>   import org.xml.sax.ErrorHandler;
>   import javax.xml.parsers;
> 
>   ...
> 
>   Writer myWriter = new CharArrayWriter();
>   ErrorHandler myErrorHandler = new ErrorHandler(myWriter);
>   SAXParserFactory factory = SAXParserFactory.newInstance();
>   SAXParser parser = factory.newSAXParser();
>   parser.setErrorHandler(myErrorHandler);  // breaks! no such method
>   parser.parse(whatever);
> 
> ...and then my ErrorHandler has a constructor that sets an output
> destination for its error messages to be the Writer that was passed
> in as an argument.
> 
> This doesn't work because setErrorHandler() doesn't exist in the
> abstract
> SAXParserFactory class. It only exists in the implementation's class
> that
> inherits from it, by virtue of that class's requirement to implement
> the
> SAX2 XMLReader interface.
> 
> It seems that I need to either work with XMLReader implementations and
> forget about using JAXP's SAXParserFactory and SAXParser, or import a
> particular implementation's classes and call them directly. This makes
> me
> wonder what the great advantage is to JAXP in SAX processing.
> 
> I thought perhaps the answer was that setErrorHandler() is not
> necessary, 
> because I could have my ErrorHandler not only implement 
> org.xml.sax.ErrorHandler, but also extend 
> org.xml.sax.helpers.DefaultHandler. Then I would have to omit the 
> ErrorHandler constructor and setErrorHandler call in the code above.
> 
> The problem with this is that I need to control the construction of
> the
> ErrorHandler so that I can have it output the error messages to a
> particular Writer. I have no idea what the implementation's SAXParser
> is
> going to do when it constructs a DefaultHandler, but I'm pretty
> certain
> there is no way for me to sneak my instance-specific Writer in there.
> 
> JAXP has an ErrorListener interface for XSLT processing errors. Why
> isn't
> there an equivalent for the XML parsing? What am I not understanding
> here?
> 
>    - Mike
> ______________________________________________________________________
> _______
> mike j. brown, software engineer at  |  xml/xslt: http://skew.org/xml/
> webb.net in denver, colorado, USA    |  personal:
> http://hyperreal.org/~mike/
> 
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