[QGIS-Developer] QGIS-Server: filter by categories in an OGC compatible way

Tue Apr 9 08:07:01 PDT 2019

Hi Paul 

Thanks - now I know that I have to use SLD_BODY for the case where the
SLD is in the URL. 

Another QGIS-Server specific question: 

Can I count on it that the SLD output by QGIS server with the GetStyles
request can also be consumed again by QGIS server? What about complex
styles (e.g. something with a style that can't easily be represented by
SLD). If I first consume the styles from QGIS server, then filter and
send back, would the complex styles potentially be lost/destroyed? 

Again: our intent here is merely to filter categories, not to change the
styles. 

Thanks,
Andreas 

On 2019-04-09 16:28, pblottiere wrote:

> Hi Andreas, 
> 
>> Can you point me to an example how to create a valid GetMap request with an SLD submitted? 
> 
> There's a basic example in unit tests: https://github.com/qgis/QGIS/blob/master/tests/src/python/test_qgsserver_wms_getmap.py#L1309-L1325
> 
> Regards,
> 
> Paul 
> 
> On 4/9/19 4:14 PM, Andreas Neumann wrote: 
> 
> Hi, 
> 
> I did some test: 
> 
> Here is a long URL with the SLD (originally sent by QGIS server, stripped away some RULES manually) and sending it back in a GetMap request: 
> 
>
https://services.geo.zg.ch/ows-oereb/Grundwasserschutz?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&BBOX=2682932,1225299,2684213,1226054&CRS=EPSG:2056&WIDTH=1615&HEIGHT=952&LAYERS=ch.zg.grundwasserschutz.gwszonen&STYLES=&FORMAT=image/png&DPI=96&MAP_RESOLUTION=96&FORMAT_OPTIONS=dpi:96&TRANSPARENT=TRUE&SLD=%3CStyledLayerDescriptor+xmlns%3D%22http%3A%2F%2Fwww.opengis.net%2Fsld%22+xmlns%3Axlink%3D%22http%3A%2F%2Fwww.w3.org%2F1999%2Fxlink%22+xmlns%3Axsi%3D%22http%3A%2F%2Fwww.w3.org%2F2001%2FXMLSchema-instance%22+xsi%3AschemaLocation%3D%22http%3A%2F%2Fwww.opengis.net%2Fsld+http%3A%2F%2Fschemas.opengis.net%2Fsld%2F1.1.0%2FStyledLayerDescriptor.xsd%22+xmlns%3Ase%3D%22http%3A%2F%2Fwww.opengis.net%2Fse%22+version%3D%221.1.0%22+xmlns%3Aogc%3D%22http%3A%2F%2Fwww.opengis.net%2Fogc%22%3E%0D%0A+%3CNamedLayer%3E%0D%0A++%3Cse%3AName%3Ech.zg.grundwasserschutz.gwszonen%3C%2Fse%3AName%3E%0D%0A++%3CUserStyle%3E%0D%0A+++%3Cse%3AName%3Edefault%3C%2Fse%3AName%3E%0D%0A+++%3Cse%3AFeatureTypeStyle%3E%0D%0A++++%3Cs
e%3ARule%3E%0D%0A+++++%3Cse%3AName%3EGrundwasserschutzzone+S1%3C%2Fse%3AName%3E%0D%0A+++++%3Cse%3ADescription%3E%0D%0A++++++%3Cse%3ATitle%3EGrundwasserschutzzone+S1%3C%2Fse%3ATitle%3E%0D%0A+++++%3C%2Fse%3ADescription%3E%0D%0A+++++%3Cogc%3AFilter+xmlns%3Aogc%3D%22http%3A%2F%2Fwww.opengis.net%2Fogc%22%3E%0D%0A++++++%3Cogc%3APropertyIsEqualTo%3E%0D%0A+++++++%3Cogc%3APropertyName%3Etyp_code%3C%2Fogc%3APropertyName%3E%0D%0A+++++++%3Cogc%3ALiteral%3ES1%3C%2Fogc%3ALiteral%3E%0D%0A++++++%3C%2Fogc%3APropertyIsEqualTo%3E%0D%0A+++++%3C%2Fogc%3AFilter%3E%0D%0A+++++%3Cse%3APolygonSymbolizer%3E%0D%0A++++++%3Cse%3AFill%3E%0D%0A+++++++%3Cse%3ASvgParameter+name%3D%22fill%22%3E%23003bb3%3C%2Fse%3ASvgParameter%3E%0D%0A++++++%3C%2Fse%3AFill%3E%0D%0A++++++%3Cse%3AStroke%3E%0D%0A+++++++%3Cse%3ASvgParameter+name%3D%22stroke%22%3E%23000080%3C%2Fse%3ASvgParameter%3E%0D%0A+++++++%3Cse%3ASvgParameter+name%3D%22stroke-width%22%3E1%3C%2Fse%3ASvgParameter%3E%0D%0A+++++++%3Cse%3ASvgParameter+name%3D%22stroke-linej
oin%22%3Ebevel%3C%2Fse%3ASvgParameter%3E%0D%0A++++++%3C%2Fse%3AStroke%3E%0D%0A+++++%3C%2Fse%3APolygonSymbolizer%3E%0D%0A++++%3C%2Fse%3ARule%3E%0D%0A+++%3C%2Fse%3AFeatureTypeStyle%3E%0D%0A++%3C%2FUserStyle%3E%0D%0A+%3C%2FNamedLayer%3E%0D%0A%3C%2FStyledLayerDescriptor%3E 
> 
> The response is:
> 
> <ServiceExceptionReport xmlns="http://www.opengis.net/ogc" version="1.3.0"> 
> 
> <ServiceException code="Invalid Parameter"> 
> SLD ('<StyledLayerDescriptor xmlns="http://www.opengis.net/sld" [1] xmlns:xlink="http://www.w3.org/1999/xlink" [2] xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" [3] xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.1.0/StyledLayerDescriptor.xsd" [4] xmlns:se="http://www.opengis.net/se" [5] version="1.1.0" xmlns:ogc="http://www.opengis.net/ogc" [6]> <NamedLayer> <se:Name>ch.zg.grundwasserschutz.gwszonen</se:Name> <UserStyle> <se:Name>default</se:Name> <se:FeatureTypeStyle> <se:Rule> <se:Name>Grundwasserschutzzone S1</se:Name> <se:Description> <se:Title>Grundwasserschutzzone S1</se:Title> </se:Description> <ogc:Filter xmlns:ogc="http://www.opengis.net/ogc" [6]> <ogc:PropertyIsEqualTo> <ogc:PropertyName>typ_code</ogc:PropertyName> <ogc:Literal>S1</ogc:Literal> </ogc:PropertyIsEqualTo> </ogc:Filter> <se:PolygonSymbolizer> <se:Fill> <se:SvgParameter name="fill">#003bb3</se:SvgParameter> </se:Fill> <se:Stroke> <se:SvgParameter
name="stroke">#000080</se:SvgParameter> <se:SvgParameter name="stroke-width">1</se:SvgParameter> <se:SvgParameter name="stroke-linejoin">bevel</se:SvgParameter> </se:Stroke> </se:PolygonSymbolizer> </se:Rule> </se:FeatureTypeStyle> </UserStyle> </NamedLayer> </StyledLayerDescriptor>') cannot be converted into QString 
> </ServiceException> 
> </ServiceExceptionReport> 
> 
> So apparently the SLD cannot be converted to a QString. Is my encoding in the URL above wrong or am I missing a required additional parameter? 
> 
> Can you point me to an example how to create a valid GetMap request with an SLD submitted? 
> 
> Thanks a lot, 
> Andreas 
> 
> On 2019-04-09 15:38, Andreas Neumann wrote: 
> 
> Hi, 
> 
> Does QGIS-Server support SLD styles to filter away RULEs in a GetMap Request? 
> 
> I would assume, yes, but in what encoding would I submit such an SLD in a GET request? I know that one should rather use POST reqests for such long parameters, but for experimenting, it would be ok to use GET. 
> 
> The idea would be to allow users to enable/disable categories within a given layer. 
> 
> The WMS client would first request the available rules with a GetStyles command (that part works fine) and would then filter the RULE (strip away the unwanted RULEs) and resubmit the GetMap with an SLD. Does that work with QGIS server? 
> 
> I know that one can also use the FILTER parameter, but we want to do it in an OGC compatible way, since the client being developed should work with any OGC compatible WMS server. 
> 
> Thanks for your reply, 
> 
> Andreas 
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Links:
------
[1] http://www.opengis.net/sld
[2] http://www.w3.org/1999/xlink
[3] http://www.w3.org/2001/XMLSchema-instance
[4]
http://www.opengis.net/sldhttp://schemas.opengis.net/sld/1.1.0/StyledLayerDescriptor.xsd
[5] http://www.opengis.net/se
[6] http://www.opengis.net/ogc
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