AFAIK nobody has tried to do this.

Last time I spoke to the hibernate guys about it, they said the rar still needs some
more work - that was back in November.

To try it, you need a hibernate-ds.xml with something like the following content

<connection-factories>
 <tx-connection-factory>

 <adapter-display-name>{The <display-name> from hibernate2.rar/META-INF/ra.xml}</adapter-display-name>

 <!-- Other config goes here -->

 </tx-connection-factory>
</connection-factories>