This you need to know

Section 9.5.3 in Spring's reference documentation explains how and when transactions are rolled back, and also states the default behaviour with respect to rolling back transactions. The behaviour might not be what you expect (quoted):

However, please note that the Spring Framework's transaction infrastructure code will, by default, only mark a transaction for rollback in the case of runtime, unchecked exceptions; that is, when the thrown exception an instance or subclass of RuntimeException. (Errors will also - by default - result in a rollback.) Checked exceptions that are thrown from a transactional method will not result in the transaction being rolled back.

Note the very last sentence (my bold). Checked exceptions do not trigger a transaction rollback!

There is of course a way change this behaviour by listing an array of Exception classes for which to roll back for, the details are in section 9.5.3 and below.

Personally I find this quite counter-intuitive, but I suppose there is good reason for this default behaviour. In either case, it's very important to be aware of how it works.