Spring @Transactional Annotation : Self Invocation

问题:

I know when a transactional method is called from inside the same class it wouldn't be run in a transaction. Spring creates a proxy for transactional methods and wraps them in a try-catch block and rolls back if an exception occurs. Consider the following scenario:

@Transactional
public void saveAB(A a, B b)
{
    saveA(a);
    saveB(b);
}

@Transactional
public void saveA(A a)
{
    dao.saveA(a);
}

@Transactional
public void saveB(B b)
{
    dao.saveB(b);
}

Assume saveAB is called from another object and an exception occurred in saveB, so saveA completed successfully but saveB did not. To my knowledge even though saveA and saveB are not transactional (because they are called from the same object), since saveAB is transactional it should still roll back.

What I don't understand is why do people say self invocation breaks transaction? As long as the caller method is transactional shouldn't everything work as expected? Is there anything I'm missing here?

回答1:

What I don't understand is why do people say self invocation breaks transaction?

I never heard that self-invocation breaks transaction. All I know is that self-invocation will not start a new transaction and you already mentioned the reason why.

Snippet from Spring's Transaction Management Specification

Note In proxy mode (which is the default), only external method calls coming in through the proxy are intercepted. This means that self-invocation, in effect, a method within the target object calling another method of the target object, will not lead to an actual transaction at runtime even if the invoked method is marked with @Transactional.

---

If you remove @Transaction annotation from saveAB(), you would observe that method saveA() and saveB() would not run under transaction even though it is annotated with @Transactional. However, if you call saveA() or saveB() from outside the class, it will run under transaction as expected. That is the reason why people advice to be cautious with self-invocation.

public void saveAB(A a, B b)
{
    saveA(a);
    saveB(b);
}

@Transactional
public void saveA(A a)
{
    dao.saveA(a);
}

@Transactional
public void saveB(B b)
{
    dao.saveB(b);
}

In my view, self-invoking any public method is a bad idea.

回答2:

If you can saveAB and saveB throws an Exception your transaction will rollback.

Seld-invocation would break transnational behaviour if saveAB was not annotated with @Transactional.

So you didn't miss anything in your example.