This a normal JPA behavior.
Once you retrieve an object via find() or so, that object is regarded as attached, or belongs to a persistence context. Once you exit the method the @Transactional triggers a Spring transaction management aspect which flushes every “dirty” object to database and commits the transaction. Since your object is already changed within the context of the persistence context and the transaction, the changes are saved to the database even without the need to explicitly call a save method.
If you want to change your object without affecting the database, you have two options:
- Update the field after returning from the method annotated with
@Transactional - If withing the method, call detach on the entity manager