On Wednesday 20 February 2008, Jody Garnett wrote:
> Mauricio Pazos wrote:
> > Hi list, I need a feature collection sorted by different attributes or
> > properties alfanumeric (no geometry attributes).
> >
> > This was my first test (it uses a shape file as feature source)
>
> Sorting hsa been added to GeoTools in 2.3, the shapefile module
> maintainer has only now moved from GeoTools 2.2 to trunk so there is a
> really good
> possibility that sorting is not implemented yet. However Jesse (in
> monday's IRC) meeting was talking about some attribute index based code
> that he was given (exactly what is needed for sorting).
>
> So why not head over to geotools-devel and let Jesse know you have a
> real use case and can help with testing :-)
Ok, I am coping this to geotools-devel and Jesse.
About the real use case, it is in uDig context (spatial operations plugin). I
need sort different type of *feature source* before process it. Geotools
provide the layer required to hide the persistence problem (interfaces and
implementations), but now I need sort technique by alfanumeric attributes. I
know shape file is an special case, but is is very popular.
>
> > DefaultQuery query = new DefaultQuery(schema.getTypeName(), filter,
> > attrNames);
> > sortProperties[0] = ..;
> > query.setSortBy(sortProperties);
> >
> > FeatureCollection featureCollection = featureSource.getFeatures(query);
>
> This is the technique that is supposed to work; you may be the first
> person to try it with shapefiles.
:D fantastic!
>
> > It returns an empty collection. I debug it and I found the following :
> >
> > AbstractFeatureSource implements FeatureSource{
> > ...
> > public FeatureColletion getFeatures(Query query){
> > ...
> > FeatureCollection collection = new DefaultFeatureResults(this,
> > query); if( collection.getDefaultGeometry() == null ){ <<<< this is
> > true!!! return collection; // no geometry no reprojection needed }
>
> Yeah that does not make sense to me ... is there code after this test
> that you was expected to run?
>
> > The collection.getDefaultGeometry == null condition is true because the
> > DataFeatureCollection 's contract doesn't allow handle the default
> > geometry.
> >
> > DataFeatureCollection
> >
> > public Geometry getDefaultGeometry() {
> > return null; <<<<
> > }
> > public void setDefaultGeometry( Geometry geometry ) throws
> > IllegalAttributeException {
> > throw new IllegalAttributeException( "DefaultGeometry not
> > supported" ); <<<<<< is not allowed
> > }
> >
> > I tried other possibilities using SubFeatureList but I haven gotten
> > success.
>
> I wrote some of the inital sorting for memory data store (using an in
> memory list of feature Ids and random accesss to return features in a
> required order).
Good news!, I am thinking in similar solution, I could
load feature's ids uning memory data store and then iterate ....
>
> > Then, What is the better approach to get an ordered feature collection?
>
> If you can use an SQL based datastore you will find they implement
> sorting and have been tested.
Yes, it is uDig then the catalogue could retrieve sql based or others
>
> > Is there any solution in geotool library? or Should I develop an ad hoc
> > solution?
>
> Test and then share your ad hoc solutions :-)
:) ok
>
> Jody
--
Mauricio Pazos
www.axios.es
tel-:+34 94 441 63 84
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