Re: [Geoserver-users] App-Schema support for level 0 simple features incorrectly attempting to cast to complex

[Andrea A. <and...@ge...>]

Hi Ursula,
in general GeoServer is written to target simple features, with localized
exceptions to also handle complex ones,
often with dedicated, separate code paths, as complex features lack a
number of optimizations that are made
easy by the flat nature of simple features.

The differentiator is not whether the schema is simple or complex, but
whether or not the SimpleFeature, SimpleFeatureType
and SimpleFeatureCollection Java classes are used to represent the
features: a flat feature built using classes that can be used
to represent complex features, is still complex to the code.

The shapefile output format has been hard coded on simple features for as
long as I can remember,
and so is the KML encoder.

DescribeFeatureType has completely separate code paths for complex and
simple, complex assumes there is
a well known target schema to abide to, and just links to it (preserving
all annotations, constraints and whatnot),
simple assumes the structure has been reflected out of a data source and
builds a bare-bone schema on the fly,
just names and types (eventually annotations too, if the database columns
have comments).

In theory, code paths could be developed that recognize what looks like a
complex feature is actually a simple one,
and transform them on the fly before they reach the output formats.
Not sure about DescribeFeatureType, as all the documentation found in your
target schemas annotations
would be lost in the complex -> simple step, but maybe one can think about
in-lining the schema, or just make the
flattening behavior optional.

The usual guide
<https://github.com/geoserver/geoserver/wiki/Successfully-requesting-and-integrating-fixes,-improvements-and-new-features-in-GeoServer>
applies in terms of making any of the above happen.

Regards,

Andrea Aime


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Ing. Andrea Aime
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GeoSolutions Group
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On Thu, Jul 11, 2024 at 5:51 AM Michael, Ursula (DEM) <
Urs...@sa...> wrote:

> UNOFFICIAL
>
> Hi Geoserver users,
>
>
>
> We have several layers built using the app-schema extension that are
> gmlsf:ComplianceLevel = 0, so are simple features, but geoserver
> incorrectly evaluating them to be complex-valued properties for some
> functionality.
>
> This means that the WFS KML and shapefile outputFormats are not available
> or throwing the below exception, and DescribeFeatureType is behaving like a
> complex service and not returning the list of fields – so impacting the
> general QGIS and ESRI wfs layer imports.
>
>
>
> <ServiceExceptionReport xmlns=http://www.opengis.net/ogc xmlns:xsi=
> http://www.w3.org/2001/XMLSchema-instance
>  version="1.2.0" xsi:schemaLocation=http://www.opengis.net/ogc
> http://schemas.opengis.net/wfs/1.0.0/OGC-exception.xsd
> <http://www.opengis.net/ogc%20http:/schemas.opengis.net/wfs/1.0.0/OGC-exception.xsd>
> >
>
> <ServiceException> java.lang.ClassCastException: class
> org.geoserver.wfs.TypeInfoCollectionWrapper$Complex cannot be cast to class
> org.geotools.data.simple.SimpleFeatureCollection
> (org.geoserver.wfs.TypeInfoCollectionWrapper$Complex and
> org.geotools.data.simple.SimpleFeatureCollection are in unnamed module of
> loader org.apache.catalina.loader.ParallelWebappClassLoader @21694e53)
> class org.geoserver.wfs.TypeInfoCollectionWrapper$Complex cannot be cast to
> class org.geotools.data.simple.SimpleFeatureCollection
> (org.geoserver.wfs.TypeInfoCollectionWrapper$Complex and
> org.geotools.data.simple.SimpleFeatureCollection are in unnamed module of
> loader org.apache.catalina.loader.ParallelWebappClassLoader
> @21694e53) </ServiceException>
>
> </ServiceExceptionReport>
>
>
>
>
>
> It also looks like the OGC API Features queryables requests are also
> unsupported
>
>
> Error: response status is 500
>
>
>
> {
>
>   "type": "NoApplicableCode",
>
>   "title": "Could not find acceptable representation"
>
> }
>
>
>
> These are a couple of the light view SF-0 schemas we are using
>
> https://schemas.opengis.net/gsml/4.1/geosciml-lite.xsd
>
>
> https://schemas.geoscience.gov.au/MineralTenementML/1.0/mineraltenementml.xsd
>
>
>
> Could this be a bug, or have all layers built using the app-schema
> extension has always interpreted the layers as complex - so new
> functionality?
>
>
>
> Kind regards,
>
> Ursula
>
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