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
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Ben Caradoc-Davies <b...@transient.nz>
Director
Transient Software Limited <http://transient.nz/>
New Zealand
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