Uses WebLogic TxHelper's static access methods to obtain
the server's internal JTA TransactionManager.
This class doesn't need be used with WebLogic 8.1 or higher, since the
regular JNDI lookup is sufficient there: it returns a JTA TransactionManager
that can handle all transaction management tasks properly.
Note that as of Spring 1.2, this class is effectively superseded by
WebLogicJtaTransactionManager's autodetection of WebLogic 7.0 or 8.1+.
It is only kept as a way to explicitly expose the JTA TransactionManager
on WebLogic 7.0, for non-Spring code that needs access to this facility.
For typical scenarios, use Spring's WebLogicJtaTransactionManager
as-is and do not bother with setting up this FactoryBean.