当在类和方法中都添加了带注释的Transactional时，如何使事务仅在方法中生效？

Question

I had an interview, and during the interview, I was asked the following question: When the @Transactional annotation is added to both the class and one method, but not on other methods, how can I only make the transaction of this method effective?

For example:

@Transactional
public class ClassA {

     @Transactional
     private void methodA() {
     } 

     private void methodB() {
     }

     private void methodC() {
     }
}

So, how can I make sure that the other transactions within the class do not take effect? What does this question focus on?

Answer 1

You can change the propagation type of the inner transaction:

@Transactional(propagation = Propagation.REQUIRES_NEW)

This will create a new inner transaction and suspend the outer transaction. This might be useful if you need an inner transaction to commit, but you need the outer transaction to still rollback if there are any issues elsewhere.

I have never used a class-scoped @Transactional , but the propagation property is actually pretty useful to know about.

I have used it in several cases to override the default, Propagation.REQUIRED , which says: 'create a new transaction if one does not already exist - otherwise support the current transaction', according to the docs.

By the way, I am using:

org.springframework.transaction.annotation.Transactional

So my answer does not apply if you are using an alternative @Transactional

Also note that the inner and outer transaction distinction is HQL-based, so you don't need to worry about the SQL dialect you're using.