XJC fails generating *.java classes

Question

I am trying to generate java classes that describe the web service offered here which belongs to this page. Please mind that I am not convinced that the XML is the one needed to run the following steps!

1. I save the XML of the API to a file: getcapabilities.xml
2. I run the following trang command to generate an XSD: java -jar trang.jar getcapabilities.xml getcapabilities.xsd
3. I get the following files: getcapabilities.xsd, ogc.xsd, wfs.xsd, xlink.xsd, xsi.xsd
4. I run the following command to generate java classes: xjc getcapabilities.xsd
5. The following error message is prompted

parsing a schema... [ERROR] no-xsi: The {target namespace} of an attribute declaration must not match 'http://www.w3.org/2001/XMLSchema-instance'.
line 7 of file:xsi.xsd
Failed to parse a schema.

Questions:

• Do you get the same error message?
• What can I do about it?
• Is my approach meant to be successful at all?

Answer 1

You're dealing with an OGC Web Feature Service. There's a couple of peculiarities with that.

• Don't generate you schemas with trang, you can get them from OGC: http://schemas.opengis.net/wfs/1.1.0/
• You don't really have to compile these schemas on your own, you can get them precompiled from the OGC Schemas and Tools project (JARs are here).
• WFS schemas only describe WFS operations - they are kind of container schemas. You'll also have an application profile which describes your features. You can obtain it via the DescribeFeatureType operation: http://data.wien.gv.at/daten/wfs?service=WFS&request=DescribeFeatureType&version=1.1.0
• Consider using someting like GeoTools.