Transaction management in Spring Boot and Spring data jpa

Question

Altough transaction management works Spring Data Repositories create their own transaction and suspend the active one.

I have following Spring application:

Application class:

@SpringBootApplication
@EnableTransactionManagement
public class SpringbootTxApplication {... }

Service class:

@Service
public class EntityService {
    ...
    public void addEntityWithoutTransaction(MyEntity myEntity) {
        log.debug("addEntityWithoutTransaction start");
        myEntityRepository.save(myEntity);
        log.debug("addEntityWithoutTransaction end");
    }

    @Transactional
    public void addEntityTransaction(MyEntity myEntity) {
        log.debug("addEntityTransaction start");
        myEntityRepository.save(myEntity);
        log.debug("addEntityTransaction end");
    }
}

While exeucting my EntityServiceTest which executes each method once and having spring transaction log in trace, I get following output:

... TRACE ... o.s.t.i.TransactionInterceptor           : Getting transaction for [de.miwoe.service.EntityService.addEntityTransaction]
... DEBUG ... de.miwoe.service.EntityService           : addEntityTransaction start
... TRACE ... o.s.t.i.TransactionInterceptor           : Getting transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.save]
... TRACE ... o.s.t.i.TransactionInterceptor           : Completing transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.save]
... DEBUG ... de.miwoe.service.EntityService           : addEntityTransaction end
... TRACE ... o.s.t.i.TransactionInterceptor           : Completing transaction for [de.miwoe.service.EntityService.addEntityTransaction]

And

... DEBUG ... de.miwoe.service.EntityService           : addEntityWithoutTransaction start
... TRACE ... o.s.t.i.TransactionInterceptor           : Getting transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.save]
... TRACE ... o.s.t.i.TransactionInterceptor           : Completing transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.save]
... DEBUG ... de.miwoe.service.EntityService           : addEntityWithoutTransaction end

Obviously according to the log, the @Transactional-Annotation is working in addEntityTransaction, but the repository still creates its own transaction.

Why? Official docs (https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#transactions) describe it should not begin a new one if it already exists.

(Sometimes, Convention over Configuration seems more like Irritation over Convention over Configuration....)

Am I missing something?

(Complete code is also available here: https://github.com/miwoe/springboot-tx)

Answer 1

Your question (main point):

... TRACE ... o.s.t.i.TransactionInterceptor           : Getting transaction for [de.miwoe.service.EntityService.addEntityTransaction]
... DEBUG ... de.miwoe.service.EntityService           : addEntityTransaction start
... TRACE ... o.s.t.i.TransactionInterceptor           : Getting transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.save]
... TRACE ... o.s.t.i.TransactionInterceptor           : Completing transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.save]
... DEBUG ... de.miwoe.service.EntityService           : addEntityTransaction end
... TRACE ... o.s.t.i.TransactionInterceptor           : Completing transaction for [de.miwoe.service.EntityService.addEntityTransaction]

Obviously according to the log, the @Transactional-Annotation is working in addEntityTransaction, but the repository still creates its own transaction.

Answer: You work inside one physical transaction.

When start call service spring starts new transaction and set TransactionStatus.isNewTransaction = true , when you call dao method spring check that method also transactional and create the second transaction for dao , BUT set for second transaction TransactionStatus.isNewTransaction = false .If you set required_new for dao method/class only in this case it be marked as TransactionStatus.isNewTransaction = true. At commit time only first transaction (physical ) is commited. If you mark the second transaction it will be ignored at commit time, and the first transaction is committed.

AbstractPlatformTransactionManager

    if (status.isNewTransaction()) {
       if (status.isDebug()) {
            logger.debug("Initiating transaction commit");
        }
        doCommit(status);
    }

You can check in debug mode.

Main point : you work inside one transaction that might be marked as commit or rollback.In TRACE you see, details about, what spring transaction does, and for you,it doesn't matter how many logical transactions creates inside on physical transaction. You have guaranty, for a transaction with propagation level REQUIRED ,that if you call the transactional method from another transaction method only one physical transaction is created and one is committed or rollbacked.

PROPAGATION_REQUIRED

When the propagation setting is PROPAGATION_REQUIRED, a logical transaction scope is created for each method upon which the setting is applied. Each such logical transaction scope can determine rollback-only status individually, with an outer transaction scope being logically independent from the inner transaction scope. Of course, in case of standard PROPAGATION_REQUIRED behavior, all these scopes will be mapped to the same physical transaction. So a rollback-only marker set in the inner transaction scope does affect the outer transaction’s chance to actually commit (as you would expect it to).

Answer 2

The repository methods are @Tranactional because you're leveraging the JpaRepository interface and allowing the framework to implement that for you.

It chooses SimpleJpaRepository by default which uses @Transactional. Take a look at the source and you'll see where it's being used.