So, this is interesting:
SynchronizationCallback from the WebSphere application server API docs...
It looks like the lookup of the extended transaction that takes place during the TransactionAdapter constructor in the websphere extended JTA adapter is taking place in the beforeCompletion method, during which access to the java: namespace is heavily restricted.
So, obviously this lookup needs to happen earlier, ideally when the transaction lookup is started.
I'm thinking of putting together a patch, in conjunction with a bug report, but it's still possible that my usage is wrong; can someone correct me?[/url]