I'm looking for a JTA implementation. I have the following requirements:

* It must be separate from any app servers. Let's assume that I am not going to deploy my application on an app server -- I just want JTA functionality within Tomcat.

* It must support XA.

* It can either be open-source or commercial, though open-source is preferred (Ideally I don't want to go through the purchasing bureaucracy of the organisation I'm working for).

Does anybody know of, or have any experience with JTA implementations that fulfil my requirements? So far I've come up with Tyrex (http://tyrex.sourceforge.net/), or JOTM (http://jotm.objectweb.org/) -- does anyone have any experience with these.

Thanks.