Modify your project POM to look something like this:

<project ...>
            The following configuration parameters are allowed:

              sourceDir (optional)
                Directory of the source tree where source code lives.

              targetDir (optional)
                Staging directory of the generated site.

              htmlHead (optional)
                Code to be included in the HTML head tag in the generated

              xsdFiles (mandatory)
                A set of XSD files to be translated to HTML.
              Add the names of XSD files here...
      <name>QXS Plugin Repository</name>

Change the configuration according to your needs. Next, generate the proxy classes:

mvn generate-sources

Note that there is usually no need for calling the generate-sources target explicitly. The result will be a set of java classes whose names start with Proxy, e.g. org.example.ProxyClassName.