Ok Ben,
Thanks a lot for the answers.
On 25 Oct 2017 22:27, "Ben Caradoc-Davies" <b...@transient.nz> wrote:
> Matteo,
>
> if the source shapefile strings started with '\0', GeoTools would have
> been reading those strings as nulls.
>
> If there are only empty strings in the shapefile, both empty strings and
> nulls will have been converted to empty strings on export from ESRI. Unless
> you have some way of telling them apart, I see no alternative to converting
> all empty strings to nulls.
>
> Kind regards,
> Ben.
>
> On 25/10/17 19:30, Matteo Cusmai wrote:
>
>> Hi Ben,
>> No I haven't.
>> The aim of my program is to store data from shapefile to database, and the
>> problem is that some fields are foreign key (not mandatory), so I have to
>> store null value not empty string.
>> I could replace the empty string in null value in my program before store
>> them into database, but I would avoid to treat each empty string as null
>> value.
>>
>> From your experience, there is another way to check if the source
>>> shapefile
>>>
>> has '\0' in those field?
>>
>>
>>
>>
>> On 24 Oct 2017 21:26, "Ben Caradoc-Davies" <b...@transient.nz> wrote:
>>
>> Matteo,
>>
>> I suspect that QGIS converts empty strings to nulls.
>>
>> Have you tried using ogr2ogr or another tool to replace empty strings with
>> strings starting with '\0'?
>>
>> Kind regards,
>> Ben.
>>
>>
>> On 24/10/17 19:20, Matteo Cusmai wrote:
>>
>> Hi Ben,
>>> Yes, I'm using esri shape file, this is a requirement.
>>> However, if I access the same files with qgis, I see null values, do you
>>> know why?
>>>
>>> On 23 Oct 2017 23:38, "Ben Caradoc-Davies" <b...@transient.nz> wrote:
>>>
>>> Matteo,
>>>
>>>>
>>>> what is the source of your data? ESRI software and the older DBF format
>>>> often used in shapefiles do not natively support nulls because all
>>>> fields
>>>> are stored as strings:
>>>> http://support.esri.com/en/technical-article/000005811
>>>> https://en.wikipedia.org/wiki/Shapefile#Data_storage
>>>> https://gis.stackexchange.com/questions/28411/how-to-have-a-
>>>> nullable-field-included-in-a-shapefile-using-the-geotools-library
>>>>
>>>> When reading a DBF file, GeoTools will treat numeric fields that are
>>>> empty
>>>> or all whitespace or start with '*' as null, and character fields that
>>>> start with a null terminator byte ('\0') as null. You can see the logic
>>>> here:
>>>> https://github.com/geotools/geotools/blob/master/modules/plu
>>>> gin/shapefile/src/main/java/org/geotools/data/shapefile/
>>>> dbf/DbaseFileReader.java#L452
>>>>
>>>> Can you use a format like geopackage that has native support for nulls?
>>>>
>>>> Kind regards,
>>>> Ben.
>>>>
>>>> On 24/10/17 01:05, Matteo Cusmai wrote:
>>>>
>>>> Hi all,
>>>>
>>>>> I need to read some shapefiles where some field are nillable and so
>>>>> they
>>>>> could have null value.
>>>>> The problem is that, I don't know why, the features has empty string
>>>>> where
>>>>> should be null.
>>>>>
>>>>> Does someone have the some problem?
>>>>>
>>>>> Regards,
>>>>>
>>>>> Matteo Cusmai
>>>>>
>>>>>
>>>>>
>>>>> ------------------------------------------------------------
>>>>> ------------------
>>>>> Check out the vibrant tech community on one of the world's most
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>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> GeoTools-GT2-Users mailing list
>>>>> GeoTools-GT2-Users@lists.sourceforge.net
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>>>>>
>>>>>
>>>>> --
>>>>>
>>>> Ben Caradoc-Davies <b...@transient.nz>
>>>> Director
>>>> Transient Software Limited <http://transient.nz/>
>>>> New Zealand
>>>>
>>>>
>>>>
>>>
> --
> Ben Caradoc-Davies <b...@transient.nz>
> Director
> Transient Software Limited <http://transient.nz/>
> New Zealand
>
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