xml-dev - Re: SAX2: Should SAXException extend IOException?

[David Brownell <david-b@pacbell.net>]

David Megginson wrote:
> 
> I especially like the idea that higher-level libraries could have
> 
>   void importXML (String uri) throws IOException;
> 
> without the application's having any direct dependency on SAX
> interfaces.

That's possible regardless of the inheritance of SAXException,
so that can't be your real motivation.


>	  It could accomplish the same thing by having a
> SAXExceptionAdapter that embeds the SAXException and extends
> IOException, but that seems like a lot of unnecessary fuss for a very
> common case.

Is that the motivation?  In my work, such cases aren't common.  I need
all basic classes of fault to get different handling paths, and it's
never been a problem to have a "throws SAXException" be one of them (or
to map all the underlying faults to some more task-appropriate reporting
models, perhaps not involving exceptions at all).

Likewise, I've always found code like

	try {
		...
	} catch (MostDerivedException e) {
		// this has to go FIRST !!!
		...
	} catch (LessDerivedException e) {
		// don't put this after LeastDerivedException
		...
	} catch (LeastDerivedException e) {
		// careful -- this has lots of subclasses
		...
	} catch (... other cases ...) {
		...
	}

to be error prone.  Often some try/catch gets written and omits critical
cases, and testing won't turn them up until a release or two is fielded
(and then it's often expensive to find and fix the problems).  Far better
to use the language's strong typing facility to have the compiler make sure
all cases are handled from day one, by not having those exceptions inherit.

- Dave
		



> Opinions?
> 
> All the best,
> 
> David
> 
> --
> David Megginson                 david@megginson.com
>            http://www.megginson.com/
> 
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