Hi,
> I don't recall that OpenJUMP can handle having a feature with no
> geometry. If nothing else, I think it would choke the renderer and
> would throw a null pointer exception. I could be wrong. Maybe one of
> the other programmers can comment.
>   
I think the same thing
> I suppose it would be possible to make the renderer ignore features
> with empty geometries. But there might be other places in the code
> where empty geometries would throw exceptions. Like when you select a
> row in an attribute table and then flash the feature on the screen or
> select it.
>   
Itoo
> I do think it is a better idea to return nulls than zeros in most
> cases. Is the regular Java null suitable for most cases when OpenJUMP
> is connecting to a database? Would it be better to train OpenJUMP to
> work with a JDBC null object or a custom object representing a null
> value from a Database?
>   
I think java null is a good approximation of what a SQL NULL is.

Michaël
> The Sunburned Surveyor
> Landon
>
> On Thu, Jan 28, 2010 at 12:51 AM, Rahkonen Jukka
> <jukka.rahko...@mmmtike.fi> wrote:
>   
>> Hi,
>>
>> It would be a correct behaviour to get nulls instead of zeros, I hope you 
>> can fix it. But check what happens if some attribute in a table or in the 
>> result set of a query contains only NULLs.  The attribute field should still 
>> appear to OpenJUMP layer schema, and it should be of a correct data type.
>>
>> More fundamental question is what to do if geometry field is NULL. It is not 
>> so uncommon situation with databases, and the aim of many GIS projects is 
>> just to add spatial data for existing objects with already known attribute 
>> data by locating them on map.
>>
>> At present if the result of a PostGIS query contains only NULL geometries 
>> OpenJUMP throws a Null Pointer Exception. If there are both real geometries 
>> and NULL geometries in the result se, the lines which are missing geometry 
>> are skipped.
>>
>> A DB Query Plugin by Larry Reeder is using a workaroud that has been very 
>> usable for me: if geometry is missing the plugin creates a default geometry 
>> as a little rectangle polygon at the origo. By that way user gets the schema 
>> and attributes to OpenJUMP even if the geometry is empty. What is missing is 
>> a clever tool for digitizing the real geometry and inserting it in place of 
>> the default geometry.
>>
>> So what do developers think about what to do with features which do not have 
>> geometry?  I am remembering that JUMP itself does not necessarily need 
>> geometry and I am rather sure that I have even seen such things in OpenJUMP. 
>> I quess I got them to OpenJUMP through opening some shapefile.
>>
>> -Jukka Rahkonen-
>>
>>
>>
>> Michaël Michaud wrote:
>>
>>     
>>> Hi,
>>>
>>> I've got a question for database experts.
>>> In DatabaseQueryPlugIn, the following JDBC methods are used to get
>>> numeric attributes from database features
>>> - ResultSet.getInt()
>>> - ResultSet.getDouble()
>>> those methods return  an int and a double, even if the
>>> database contains
>>> NULL
>>> NULL : getInt() --> 0
>>> NULL : getDouble() --> 0.0
>>> I think that OpenJUMP should get a null value each time the database
>>> contains a NULL value.
>>>
>>> If this there is no special reason to use those methods, I'll
>>> change the
>>> code to get null instead of 0 in this special cases.
>>>
>>> Thanks for any suggestion
>>>
>>> Michaël
>>>
>>> NB : I noticed another problem with null handling in
>>> SimpleQueryPlugIn.
>>> I fixed it in the svn that way :
>>> select features from layer1 where name = (empty combo box)
>>> now returns
>>> empty strings AND nulls (empty strings and null are very similar from
>>> the end-user point of view)
>>> I added "is null" as a function to be able to differentiate null from
>>> empty string cases
>>> There maybe some corner cases  which are still not perfectly handled
>>> (when there are null in the dataset and the operator is not
>>> "equal" for
>>> example)
>>>
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