Spring/Hibernate @Transactional pitfall

We’re currently doing a student project which I hope to show off in the future. EDIT: it’s about https://teiler.io. However, yesterday I ran into a problem where I want to document the fix.

We have a repository method that is marked as @Transactional to delete a certain row. At first, we called that in a loop, from a method from one of our @Service classes and it worked fine. 

We then refactored it and added a method to the repository, which accepts a list and then does the looping for us, calling the other repository method in the loop. Then stuff broke. 

We got a lot of the following messages:

org.springframework.dao.InvalidDataAccessApiUsageException: No EntityManager with actual transaction available for current thread - cannot reliably process ‘remove’ call

The part “No EntityManager with actual transaction available for current thread” points to a transaction problem, which happens when you don’t use @Transactional. But we did. So what happens? 

Remember that annotations are worked out by using reflection. And reflection is, sometimes, a bit magic. And here it failed. 

The problem was, that the @Transactional on the actual remove method wasn’t picked up, when it was called from another method in the repository. So no transaction was started. 

To fix this, you have to add @Transactional to the method you call from outside your class - the one that accepted the list. That fixed the problem!