Javadoc
Listens for UserTransaction events and handles associating the extended persistence context with the JTA transaction.
JPA 2.0 section 7.9.1 Container Responsibilities:
"For stateful session beans with extended persistence contexts:
When a business method of the stateful session bean is invoked, if the stateful session bean
uses bean managed transaction demarcation and a UserTransaction is begun within the
method, the container associates the persistence context with the JTA transaction and calls
EntityManager.joinTransaction.
"