Why Catching an Exception Doesn't Prevent Spring Transaction Rollback

Last week we explained why the test4 method rolled back even though the exception was caught, referencing the article “Why catching an exception still rolls back the transaction?”.

Many still wonder why a javax.validation.ConstraintViolationException is not caught in test4. The reason is simple: the exception is thrown after the try‑catch block finishes, so the catch block never sees it.

Hands‑on Experiment

The @Transactional annotation works via an AOP proxy, so understanding the flow requires looking at the source code. To see why test4’s catch does not capture the exception, add logging and breakpoints around the method and the transaction commit point.

Insert additional log statements and breakpoints in test4, then set a breakpoint at the transaction commit entry point ( org.springframework.orm.jpa.JpaTransactionManager.doCommit).

When running in DEBUG mode you will see that all lines in test4 execute except line 47, after which control moves to JpaTransactionManager.doCommit. The rollback exception is thrown after the try‑catch block, so the catch block cannot intercept it.

The execution order can be observed in the following diagram:

By debugging the Spring source you can gain a deeper understanding of transaction mechanics and avoid similar confusion in the future.