[opencms-dev] How to access a OpenCmsVfsFile in an xml

[Marc Schlegel]

My template makes use of xml-configuration-files like TemplateOne does. 
In case of my css-config, everything works fine when using 
getStringValue from org.opencms.xml.A_CmsXmlDocument. But when trying to 
get a OpenCmsVfsFile the method is jumping into to catch-block when calling

value = m_configuration.getStringValue(getCmsObject(), key, 
getRequestContext().getLocale());

I am sure that the catch-block is called cause I places a 
System.out.println before and after.
How can I access a OpenCmsvfsFile-Entry in my xml?

Thanks