I am not happy with what I just committed for CXF-1391. The problem is that both ObjectType and BeanType think that they are in charge of xsi:type. ObjectType wrote it out unconditionally, BeanType based on conditions, and then some parsers decided to blow a gasket when the thing occurred twice (which is what I got when I fixed the tendency it had not to show up at all). My fix works, but it's fairly repulsive. I'm open to suggestions.
