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   RE: Exceptions or not (Was: RE: ModSAX (SAX 1.1) Proposal)

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  • From: Jarle Stabell <jarle.stabell@dokpro.uio.no>
  • To: "'xml-dev@ic.ac.uk'" <xml-dev@ic.ac.uk>
  • Date: Wed, 17 Feb 1999 17:30:12 +0100

David Megginson wrote:
> Jarle Stabell writes:
>  > I haven't used Java much, so personally I don't know whether I find
>  > this forced declarations of exception throwing a good thing.  (It
>  > seems to me quite a lot of people throws in the towel and just
>  > writes "throws exception")
> Sure, it can get to that point, but then the exception falls off the
> top level, and you still end up with some useful information about
> where your bug was, so you're still better off than you would have
> been.

True. I love exceptions and find that they greatly improves the robustness 
of applications, but the reason I'm not convinced about whether it is good 
to be forced to specify what will be thrown is that this in many cases seem 
to require psychic powers of the designer (or that the "real" exceptions 
must be catched and converted into an "acceptable" one, which looses 

> Besides, "throws Exception" requires a conscious effort to turn off
> the safety mechanisms.

Not when you are desperate or in a hurry! ;-)

>   boolean hasNamespaces = true;
>   boolean hasXLink = true;
>   boolean hasDDML = true;
>   boolean hasXPointer = true;
>   try {
>     parser.setFeature("com.foo.features.namespaces", true);
>   } catch (SAXNotSupportedException e) {
>     hasNamespaces = false;
>   }
>   try {
>     parser.setFeature("com.foo.features.xlink", true);
>   } catch (SAXNotSupportedException e) {
>     hasXLink = false;
>   }
>   try {
>     parser.setFeature("com.foo.features.ddml", true);
>   } catch (SAXNotSupportedException e) {
>     hasDDML = false;
>   }
>   try {
>     parser.setFeature("com.foo.features.xpointer", true);
>   } catch (SAXNotSupportedException e) {
>     hasXPointer = false;
>   }

I meant that the SetFeature should return a boolean, not necessarily 
introduce/use a special supportsFeature method. Then one could use 
something like (haven't used Java in a while, so this may contain errors!):

boolean hasNamespaces = parser.setFeature("com.foo.features.namespaces", 
boolean hasXLink = parser.setFeature("com.foo.features.xlink", true);
boolean hasDDML = parser.setFeature("com.foo.features.ddml", true);
boolean hasXPointer = parser.setFeature("com.foo.features.xpointer", true);

and then you could analyze the results, or put some analyzis in between the 
above calls.

Jarle Stabell

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