[mapguide-internals] Exception thrown on null values?

[Traian Stanev]

Hmm... always doing an IsNull() for everything has an overhead as well -- internally to the provider it may be equivalent to getting the property twice. Once to check for null and another time to get the property value.

Traian



> -----Original Message-----
> From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-
> internals-bounces at lists.osgeo.org] On Behalf Of Bruce Dechant
> Sent: Thursday, February 28, 2008 5:05 PM
> To: MapGuide Internals Mail List
> Subject: RE: [mapguide-internals] Exception thrown on null values?
>
> Jason,
>
> This is the expected behavior as Traian pointed out. This was changed
> from what it was before because now we do the IsNull() check internally
> in the server on all GetXXX() APIs just in case the user "forgot" to
> call it. This was also done to prevent memory access violations when
> trying to call for example GetString() from a reader that has a NULL
> property value and the underlying provider tries to do the read string
> and then crashes, by adding this check we have added some server
> stability.
>
> Not all providers are created equally. :)
>
> Thanks,
> Bruce
>
>
> -----Original Message-----
> From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-
> internals-bounces at lists.osgeo.org] On Behalf Of Jason Birch
> Sent: Thursday, February 28, 2008 2:48 PM
> To: MapGuide Internals Mail List
> Subject: RE: [mapguide-internals] Exception thrown on null values?
>
> Am I allowed to say "lame"?  :)  NULL is a perfectly valid value for
> most data types, and throwing an exception in this case adds a lot of
> additional processing that should not be required.
>
> I personally feel that this is a case where MapGuide could make
> application developers lives a lot easier and improve (slightly?) the
> performance of web-level apps by swallowing the exception and returning
> NULL.
>
> Jason
>
> -----Original Message-----
> From: mapguide-internals-bounces at lists.osgeo.org
> [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Traian
> Stanev
> Sent: Thursday, February 28, 2008 13:31
> To: 'MapGuide Internals Mail List'
> Subject: RE: [mapguide-internals] Exception thrown on null values?
>
> I think this complies with the FDO spec, which requires an exception to
> be thrown when the value is null and you try to get it anyway. The two
> solutions are to check for IsNull() before getting it, or to catch the
> exception. The code *could* in theory return NULL in this case, but...
>
> Traian
>
> > -----Original Message-----
> > From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-
> > internals-bounces at lists.osgeo.org] On Behalf Of Jason Birch
> > Sent: Thursday, February 28, 2008 4:29 PM
> > To: MapGuide Internals Mail List
> > Subject: [mapguide-internals] Exception thrown on null values?
> >
> > Hi,
> >
> > I'm seeing a case in MGOS 2.0 where MgFeatureReader->GetString() is
> > throwing an exception when the value of the string is null.
> >
> > Is this expected behaviour?  Has it changed since 1.2?  I believe
> that
> > I've seen a similar error in geometry, but don't have a test case for
> > that yet.
> >
> > This is relatively easy to work around with a try/catch and
> suppressing
> > the error output if the message includes "null", but it's a bit
> > annoying.  Is there a better way of dealing with this?
> >
> > Jason
> > _______________________________________________
> > mapguide-internals mailing list
> > mapguide-internals at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/mapguide-internals
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