[Geoserver-users] Why does GetFeature return feature 5 times?

GeoServer GeoServer User
1

When I execute the GetFeature request [1] against a geoserver 2.1.1 instance I get a gml-string with just 1 feature in the feature-collection (as expected). When I execute the same request against a geoserver 2.3.5 instance the feature collection contains this feature 5 times for some reason.

[1] geoserver/wfs?OUTPUTFORMAT=GML2&PROPERTYNAME=uid,GeoNode,node_type,owner,system_type&REQUEST=GetFeature&TYPENAME=JAGIS:Knopen&VERSION=1.1.0&CQL_FILTER=“uid” IN (‘0CAD0CF7A2E8437FA019F45BF79B344F’)

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2

On Tue, Sep 10, 2013 at 1:46 PM, Roel De Nijs <roel.denijs@anonymised.com>wrote:

When I execute the GetFeature request [1] against a geoserver 2.1.1
instance I get a gml-string with just 1 feature in the feature-collection
(as expected). When I execute the same request against a geoserver 2.3.5
instance the feature collection contains this feature 5 times for some
reason.

[1]
geoserver/wfs?OUTPUTFORMAT=GML2&PROPERTYNAME=uid,GeoNode,node_type,owner,system_type&REQUEST=GetFeature&TYPENAME=JAGIS:Knopen&VERSION=1.1.0&CQL_FILTER="uid"
IN ('0CAD0CF7A2E8437FA019F45BF79B344F')

You'll have to be more specific to have any chance to get an answer. Are
you using app-schema in your feature type?
Can you provide a detailed description of how that feature type is setup?

Cheers
Andrea

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3

geowolf wrote

You'll have to be more specific to have any chance to get an answer. Are
you using app-schema in your feature type?
Can you provide a detailed description of how that feature type is setup?

No, we are not using app-schema plugin. All our layers (feature types) are
based on tables (or views) from a Microsoft SQL Server JNDI data source.

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4

I upgraded geoserver to the latest 2.4.0 release, unfortunately this issue
still occurs. I was able to do some extra tests now and I guess I found the
cause (and also a solution).

For some reason the PROPERTYNAME parameter influences the size of the
feature collection. When this parameter contains 5 attributes, the feature
collection contains this feature 5 times. When this parameter contains just
3 attributes, the feature only appears 3 times in the collection. When I
remove the PROPERTYNAME parameter from the request, the feature collection
has the feature just once.

When I add "service=wfs" to the request, the number of attributes of the
PROPERTYNAME parameter has no influence anymore on the size of the feature
collection. The requested feature appears just once in the feature
collection (as expected).

So I wonder why there is such a difference in behavior between a request
with or without the "service=wfs" part? I would assume it has something to
do with And the difference between both gets even bigger when the
PROPERTYNAME parameter has just 1 attribute: without the "service=wfs" part
the request results in an exception (/java.lang.ClassCastException:
java.lang.String cannot be cast to java.util.Collection java.lang.String
cannot be cast to java.util.Collection/), whereas with the part the request
returns the requested feature.
I would assume if the "service=wfs" part is required to execute the request
correctly, not providing this value would result in an exception unless
there is some backwards compatibility involved...

Kind regards,
Roel

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5

Hi,

It may be hard for the developers to decide how kind to be for users. There should be no danger of misinterpretation with GetFeature even without service because no other OGC service has that request. However WFS 1.1.0 standard says:

"The mandatory SERVICE parameter specifies which of the available service types at a particular service instance is being invoked. The value WFS is used to indicate that the Web Feature Service should be invoked."

Geoserver could do schema validation and be strict but that would mean that your service=wfs would also fail because it should be service=WFS. And getfeature would fail because it is officially GetFeature. That would make some users to say that Geoserver is nit-picky. Try deegree and you will see what I mean
http://inspire.kademo.nl/deegree-wfs/services?SERVICE=WFS&VERSION=1.1.0&REQUEST=getcapabilities

Problem with being kind is that all non-standard variations can't be tested. Perhaps best you can do is to try to follow the lexicon of standard more strictly on your side. Making Geoserver more strict would for sure break many existing applications.

-Jukka Rahkonen-

________________________________________
Lähettäjä: Roel De Nijs [roel.denijs@anonymised.com]
Lähetetty: 25. syyskuuta 2013 19:22
Vastaanottaja: geoserver-users@lists.sourceforge.net
Aihe: Re: [Geoserver-users] Why does GetFeature return feature 5 times?

I upgraded geoserver to the latest 2.4.0 release, unfortunately this issue
still occurs. I was able to do some extra tests now and I guess I found the
cause (and also a solution).

For some reason the PROPERTYNAME parameter influences the size of the
feature collection. When this parameter contains 5 attributes, the feature
collection contains this feature 5 times. When this parameter contains just
3 attributes, the feature only appears 3 times in the collection. When I
remove the PROPERTYNAME parameter from the request, the feature collection
has the feature just once.

When I add "service=wfs" to the request, the number of attributes of the
PROPERTYNAME parameter has no influence anymore on the size of the feature
collection. The requested feature appears just once in the feature
collection (as expected).

So I wonder why there is such a difference in behavior between a request
with or without the "service=wfs" part? I would assume it has something to
do with And the difference between both gets even bigger when the
PROPERTYNAME parameter has just 1 attribute: without the "service=wfs" part
the request results in an exception (/java.lang.ClassCastException:
java.lang.String cannot be cast to java.util.Collection java.lang.String
cannot be cast to java.util.Collection/), whereas with the part the request
returns the requested feature.
I would assume if the "service=wfs" part is required to execute the request
correctly, not providing this value would result in an exception unless
there is some backwards compatibility involved...

Kind regards,
Roel

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6

Rahkonen Jukka wrote

Geoserver could do schema validation and be strict but that would mean
that your service=wfs would also fail because it should be service=WFS.
And getfeature would fail because it is officially GetFeature. That would
make some users to say that Geoserver is nit-picky. Try deegree and you
will see what I mean
http://inspire.kademo.nl/deegree-wfs/services?SERVICE=WFS&VERSION=1.1.0&REQUEST=getcapabilities

I really like the deegree example! It gives a clear and obvious exception
message about what's wrong with the request and then it's up to the user to
make the appropriate changes. I would not complain about deegree being too
nit-picky. I'm living in a java world and it's case-sensitive: I know
GetFeature isn't the same as getfeature or getFeature.
But others will really like the kindness of Geoserver and making it now more
strict would indeed break many, many existing applications. So that's a
no-no.

On the other hand I think there is no harm in implementing a minimal schema
validation. Just checking if the required parameters for a request are
present would be a good practice. If a required parameter is missing the
request is actually invalid and the outcome would be unpredictable. The user
should be informed about his mistake, instead of suddenly getting a weird
result after upgrading to the latest version.

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