AT:

• log Exception
  No JTA UserTransaction available - programmatic PlatformTransactionManager.getTransaction usage not supported
  on level FINE

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In the signal()-method after an asynchronous call an exception is raised. During rollback() another exception is thrown on Websphere Application Server 8.5.:
"org.springframework.transaction.CannotCreateTransactionException: No JTA UserTransaction available - programmatic PlatformTransactionManager.getTransaction usage not supported".

I attached a simple test project to replicate this behaviour. I think there should be no uncaught exception thrown during transaction rollback.
At least this is the behaviour the test application is showing on JBoss.