Questions posées lors d’un entretien d’embauche pour Java/Full Stack Developer chez IBM

Transactional method calls non-transactional method. If non-transactional method fails, will transaction rollback?

Counter value incremented inside transaction. If transaction fails, class value updated? @Service public class PaymentService { private int counter = 0; @Transactional public void processPayment() { counter++; paymentRepository.save(payment); throw new RuntimeException("Failed"); } }

Payment debited successfully, but response failed. Client retries and amount debited twice. How prevent?