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Re: Seeking SAXException pattern

• To: Tim Bray <tbray@t...>
• Subject: Re: Seeking SAXException pattern
• From: Mik Lernout <mik@f...>
• Date: Sun, 28 Nov 2004 12:04:51 +0100
• Cc: xml-dev@l...
• In-reply-to: <D369065E-40D3-11D9-BB2B-000A95A51C9E@t...>
• References: <D369065E-40D3-11D9-BB2B-000A95A51C9E@t...>
• User-agent: Mozilla Thunderbird 0.8 (Windows/20040913)

Tim,

Well, you hit one of the dirtier chapters in the SAX usage story. The 
SAXException denotes that something is wrong with the parsed document: 
it is not XML correct OR it contains bogus data according to your 
ContentHandler. It kinda makes sense in a Java way. Keeping that in mind 
you could do something like this:

Make a class called TimBraySAXException:
public class TimBraySAXException extends SAXException { //details.. }

Change your ContentHandlers to use:
  try
  {
    myValidationCode(s, start, length);
  }
  catch (Exception e)
  {
    throw new TimBraySAXException (e);
  }


And you do not have to do any picking anymore:
  try
  {
    xmlReader.parse("mydoc.xml");
  }
  catch (TimBraySAXException e)
  {
    //do one thing
  }
  catch (SAXException e)
  {
    //do other, probably less interesting, thing.
  }

Hope that helps!

Mik Lernout

Tim Bray wrote:

> I'm writing some java code that uses a basic SAX parser, and I haven't 
> done this for years if ever, and the callback routines all have 
> signatures that throw SAXExceptions, e.g.
>
>   public void characters(char [] s, int start, int length)
>     throws SAXException
>
> So, suppose I'm in this callback and something horrible happens; for 
> example I discover that the content that I'm looking at here is 
> completely bogus.  I can't throw an Exception of any kind without 
> screwing up the signature.  So I have this pattern all over my code.
>
>   try
>   {
>     myValidationCode(s, start, length);
>   }
>   catch (Exception e)
>   {
>     throw new SAXException(e);
>   }
>
> And then I have to catch the SAXException and pick it apart to see if 
> it's really one of mine.  All of which seems kind of dorky.  I'm sure 
> there must be a standard good practice that's been developed here?  -Tim
>
>
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• Follow-Ups:
  • RE: Seeking SAXException pattern
    • From: "Michael Kay" <michael.h.kay@n...>
  • Re: Seeking SAXException pattern
    • From: Elliotte Harold <elharo@m...>

• References:
  • Seeking SAXException pattern
    • From: Tim Bray <tbray@t...>

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