Here is a nice tool that can take care of back-end system integration and java transaction management. The Transactions product is a JTA (java transaction API) implementation with full recovery under the hood. It integrates with most J2EE application servers as well as with J2SE applications, and adds transactional robustness, and automatic recovery on-the-fly. Perfect for your online transaction processing (OLTP)!
Some of the supported application servers are:
-Tomcat (JTA transactions)
-JBoss (JTA transactions with RMI/IIOP support)
-ServletExec (by New Atlanta)
Here is more information about transaction processing software.
Alternatively, go directly to the JTA download.