On 01/12/2006, at 10:46 PM, Andrus Adamchik wrote:
> I am taking this discussion to cayenne-dev from Jira. Essentially
> this is about whether Ordering (and Expression I guess) should
> throw on nulls in the middle of the property path (like OGNL does)
> or return NULL (like WebObjects does).
>
> I can think of one problem with returning nulls: we won't be
> comparing apples to apples ("painting.artist == null" is not the
> same as "painting.artist.name == null"). But of course it is a nice
> shortcut...
In terms of utility to the developer, the current behaviour is
problematic. It means that for every relation which could possibly be
NULL, then we cannot use the Cayenne sorting functionality. We might
have 100,000 records and one NULL value, but we then cannot sort.
It seems that even OGNL allows NullPointerExceptions to be
overridden. http://www.ognl.org/2.6.9/Documentation/html/
DeveloperGuide/nullHandler.html
Perhaps the equivalent of this OGNL idea is to be able to map
"painting.artist == null" to "No linked artist" or some other
arbitrary value and "painting.artist.name == null" to "No name". Then
they might be sorted alphabetically under "N". But personally I think
this is overkill and not really needed. Grouping them all as null,
without distinguishing the type of null, would be simpler.
Ari Maniatis
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