Spring / Hibernate @Transactional 不刷新事务，如果后跟第二个 @Transactional 调用

Question

I have a weird behaviour in my Spring Boot App.

The app have the OpenSessionInView to false .

I have a Controller and a Service exposing 2 methods with annotation @Transactionnal .

Application.properties:

spring.jpa.open-in-view=false

My service:

@Service
public class MyService {
        @Transactional(transactionManager = "myTx")
        public void doA(Integer objectId) {
                Object o = repo.findMyObject(objectId);
                updateMyObject(o);
                repo.save(o);
        }

        @Transactional(transactionManager = "myTx")
        public void doB(Integer objectId) {
                Object o = repo.findMyObject(objectId);
                updateMyObjectDifferently(o);
                repo.save(o);
        }
}

My Controller (case 1):

@RequestMapping("/do/{myId}")
    public String do(Model model, HttpServletRequest request) {

        service.doA(myId);
        service.doB(myId);

        return "page";
    }

With SQL in debug, I see that the SELECT queries are performed during the call to the service. But I see only 1 flush (several UPDATES) , and it's done when service.doB() is finished and the TransactionInterceptor around the method launch the method invokeWithinTransaction which is weird.

As both method have @Transactional, I was hoping to see 2 flush : the first flush just at the end of service.doA() and a second flush at the end of service.doB().

What is more weird is that if I comment the second call, so

My Controller (case 2):

@RequestMapping("/do/{myId}")
    public String do(Model model, HttpServletRequest request) {

        service.doA(myId);
        //service.doB(myId);

        return "page";
    }

In case 1, it's like service.doA() knows that a second call will arrive just after on the same object, so it does not commit/flush the transaction and wait for the end of service.doB().

Why do I see only 1 flush? Is it because both calls are on the some DB object?

I thought my knowledge of @Transactional were ok. But now, I am lost.

Answer 1

Hibernate will detect if an object really is dirty and avoid sending an UPDATE statement if it's not necessary. I assume that your updateMyObject is simply not changing the state of the entity with respect to the state it had initially when it was loaded.