Using UserTransaction interfacr instead of TransactionManager interface in tx mediator

I am not sure why the TransactionManager interface was used when implementing the tx mediator. But the documentation says when we need to move the tx mangement boundries to application server we need to use TransactionManager interface.
How ever using this(TransactionManager) with more that one data sources caused me resource enlist exception. So I just switched to UserTransaction Interface and then it works fine with more than one datasources. I am attaching the changes as a patch. (If anybody interested I can attach the configuration files used.)