During the Struts Action 2 meetup, we discussed the design of an annotation-based validation framework, which in turn led to questions about overriding annotations with XML. Ideally you would reuse the annotation classes directly, but I can't find a way to instantiate them! That's not very unit test friendly. I suppose a framework could modify the class bytecode at load time based on the XML, but that would only allow one set of overrides per Class instance. I guess it's time to submit a JSR...