Although it’s a bit late for a reply:
Apparently, at least for me, the Java Loader documentation is a bit unclear with resp. to the use of root-elements vs. collections. This is how I got it working:
The root-node of the XML-Loaderfile has to be identical to the name of the collections you intend to store the data to.
The second element of this file (which in individual documents would corresponds to the root)is the doctype.
Vice-Versa: If you’d use the Interactive Interface, the root element of the individual file you want to “process” in order to load would have to be the second one of the above.
Java Load: …
Interactive: , with collection set to ArtRoot