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Re: [udig-users] WMS and no access to XSDs for schema validation 
Hi Frank,

Am 05.10.2020 um 21:20 schrieb Frank Gasdorf:

welcome to the users-list and thanks for your post!


thanks for the quick answer!
Have I understood you correctly, the added WMS Server/Layer has not been added to the Map/Catalog due to this validation error? Maybe this error is just logged but ignored at  the end.
After closing the "Add layer" wizard the WMS server is added to the catalog view. If I click on this new entry new entry in the catalog view the following error message appears in red in status bar: 

(this is the original message in german)
"Keine Verbindung zum WMS. Möglicher Grund: Error downloading http://schemas.opengis.net/sld/1.1.0/sld_capabilities.xsd";
(Translation: "No connection to WMS. Possible cause: Error downloading http://schemas.opengis.net/sld/1.1.0/sld_capabilities.xsd)
I found a similar report on Stackoverflow (https://stackoverflow.com/questions/29073622/geotools-wms-module-error).
This seems like a solution of the problem to me. I already asked the admin of the WMS server if it's possible for him to change the server config to add only URLs to local XSD files in the schema location attribute of the GetCapabilities response.
Then I found a GeoTools - FAQ entry : https://docs.geotools.org/latest/userguide/faq.html#q-i-am-in-a-restricted-environment-how-to-configure-schemalocator
I also found this FAQ entry the last days during my research for a solution. In this FAQ the GeoTools developers basically say that they used the mentioned approach to force XML parsers to use copies of schema files included in GeoTools jars instead of downloading the schema each time.
This made me think that GeoTools also does not download the XSDs usually needed for WMS or WFS. And the link to the GeoTools architecture in my previous post seemed to confirm this. There they say
"To support the XML module in GeoTools we have bundled up several XML schemas in JAR form (to prevent needing to download them from the Internet each time they are needed). " And then they list the JARs like gt-xsd-wms and net-opengis.ows. My conclusion was that GeoTools by default uses local XSDs.
But in my case it seems that at least one XSD is not contained in the mentioned GeoTools JARs. Perhaps it's really a GeoTools problem.
I'm trying to perform a test with the latest uDig 2.2.0 RC1 to see if this problem still exists with the newer GeoTools 22.1.
Would you please create an issue at github (https://github.com/locationtech/udig-platform/issues) so we can dig into uDig and find a way to solve it. I guess it needs more investigation.. 



I will create the issue as soon as possible.


Many thanks in advance


No problem. I'm glad to help.

Thanks,
Riccardo


--
Frank
Am Mo., 5. Okt. 2020 um 15:48 Uhr schrieb Riccardo Foschia <riccardo.foschia@xxxxxxxxxxxxx <mailto:riccardo.foschia@xxxxxxxxxxxxx>>: 

    Hello udig-users,

    this is probably more a GeoTools problem but it happens with uDig, so I
    ask this list first:

    I'm running uDig 2.0.0 on a machine without internet access.

    Unfortunately I cannot add a WMS layer to a uDig map from a WMS server
    in the same LAN as the machine running uDig. In the status bar uDig
    complains it cannot connect to the WMS because of

    "Error downloading
    http://schemas.opengis.net/sld/1.1.0/sld_capabilities.xsd";

    I'm suspecting that uDig or better GeoTools tries to access some of the
    URLs to the XSD referenced in the XML file returned by the
    GetCapabilities request to the local WMS. For your information: these
    are the first lines of the GetCapablities response:

    <?xml version='1.0' encoding="UTF-8" standalone="no" ?>
    <WMS_Capabilities version="1.3.0"  xmlns="http://www.opengis.net/wms";
    xmlns:sld="http://www.opengis.net/sld";
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
    xmlns:ms="http://mapserver.gis.umn.edu/mapserver";
    xsi:schemaLocation="http://www.opengis.net/wms
    http://schemas.opengis.net/wms/1.3.0/capabilities_1_3_0.xsd
    http://www.opengis.net/sld
    http://schemas.opengis.net/sld/1.1.0/sld_capabilities.xsd
    http://mapserver.gis.umn.edu/mapserver";>


    I did some research and it seems to me that GeoTools should by default
    not access the internet when parsing GetCapabilities responses if some
    JARs (gt-xsd-*.jar and net.opengis.*.jar) are distributed with an
    application, see chapter "GeoToolsExtensions / XML" here

    https://docs.geotools.org/latest/userguide/welcome/architecture.html

    I checked that the GeoTools JARs mentioned in the above document are
    distributed with uDig 2.0.0. They are also listed in bundle
    classpath of
    org.locationtech.udig.libs plugin.

    It would be OK for me, if no validation at all would happen for the
    used
    WMS. So my question is:

    Is there a way to configure uDig that no schema validation happens for
    responses to WMS requests?

    Any hints are really appreciated.

    Thanks in advance,
    Riccardo
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META-LEVEL Software AG
Lyonerring 1
66121 Saarbrücken
Deutschland
Tel: +49 - 681 / 99687-0
Fax: +49 - 681 / 99687-99
Mail: info@xxxxxxxxxxxxx
Web: www.meta-level.de

Rechtsform: Aktiengesellschaft
Sitz: Saarbrücken
HR B Nr. 13 380 Amtsgericht Saarbrücken
USt-IdNr. DE 1 38 166667
Vorstände: Dipl.-Inform. Peter Badt und Dipl.-Inform. Peter Raber
Vorsitzender des Aufsichtsrats:  Reinhard Kuhn

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