Improve wording on transactional methods inherited from SimpleJpaRepository and repository fragments

[vananiev]

Transactionality documentation sectional may mislead about apply @Transactional for custom repository, which extends JpaRepository (proof).

Spring JPA JavaDoc may be clarified by this PR.

Tests:
I test

public interface SecurityRepository extends JpaRepository<SecurityEntity, String> {
    Collection<SecurityEntity> findByIdStartingWith(String with);
}

method call with property

logging.level.org.springframework.transaction.interceptor = TRACE

When no @Transactional on class or method, transaction for custom method is not created

o.s.t.i.TransactionInterceptor           : No need to create transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.findByIdStartingWith]: This method is not transactional.

With annotation on class or method level transaction is created

o.s.t.i.TransactionInterceptor           : Getting transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.findByIdStartingWith]
o.s.t.i.TransactionInterceptor           : Completing transaction for [org.springframework.data.jpa.repository.support.SimpleJpaRepository.findByIdStartingWith]

[mp911de]

Actually, methods on JpaRepository and JpaSpecificationExecutor are transactional as SimpleJpaRepository is marked as @Transactional(readOnly = true).

[vananiev]

Yes. You give measlead answer as documentation. That's a problem. Does your answer follow that SecurityRepository .findByIdStartingWith() is tarnsactional? Test shows that no.

[mp911de]

Does your answer follow that SecurityRepository .findByIdStartingWith() is tarnsactional? Test shows that no.

findByIdStartingWith(…) is not declared on JpaRepository or JpaSpecificationExecutor, it is declared on SecurityRepository and likely it isn't annotated with @Transactional.

Therefore your observation is correct. Note that transactional attributes defined on SimpleJpaRepository (which is the primary implementation of JpaRepository and JpaSpecificationExecutor) do not affect query methods you declare on your repository unless you override a method of JpaRepository or JpaSpecificationExecutor.

[vananiev]

Yes, but doc says about [all] CRUD methods of repository

By default, CRUD methods on repository instances are transactional

This part may be clarified by this PR.

[mp911de]

This part may be clarified by this PR.

This PR addresses only a subset, so my intent is rather to mention both interfaces to document the exact behavior to expect.

[vananiev]

Ok, will you make it yourself or my help required?

[mp911de]

I can take it if you don't mind.

[vananiev]

Ok, but I want to to check if explanation will be clean.