If you need to perform textual comparison of XML documents, there are better ways of doing it than by trying to control the output of an XML framework that does not distinguish between attribute ordering.
For example, there's XMLUnit, which is a junit extension specifically for XML assertions, and it handles whitespace and ordering quite nicely.
A more general solution is XOM's Canonicalizer, which outputs XML DOMs such that the attribute ordering and whitespace is predictable. Very handy.
So... let JAXB (or whatever) generate the XML as it sees fit, then run the outputs through XMLUnit or XOM, and compare. This has the added advantage of not depending on JAXB, it'll work with any generated XML.
