UsernamePrincipal implements Serializable ?

[Marvin S. Addison]

> I do think we need to look at pulling in a JSON library as a compact
> serialization format, though in most cases, XML will do fine for
> now.

If you're going for compactness and human readability, JSON is a good 
choice. If you're optimizing for both speed and size, it's hard to beat 
Kryo, http://code.google.com/p/kryo/. The following Gist compares Kryo 
with default Java serialization:

https://gist.github.com/serac/2007751

Fairly readable besides.

M