Java.Hibernate.Beginner.Do i need openSession in SpringBoot ?

No, you almost never need to manually call openSession() in a typical Spring Boot application. Spring Boot, through Spring Data JPA or Spring’s @Transactional support, manages the Hibernate session lifecycle automatically for you.

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🔹 How it works in Spring Boot:

• When you annotate a method or class with @Transactional, Spring opens a Hibernate session behind the scenes, binds it to the current thread, and manages:
  • Starting a transaction,
  • Flushing changes,
  • Committing or rolling back the transaction,
  • Closing the session automatically when your method finishes.
• For example:

@Service
public class UserService {
    @Transactional
    public void updateUsername(Long id, String newName) {
        User user = entityManager.find(User.class, id); // Hibernate session is already active here
        user.setUsername(newName);                      // changes tracked
        // session flush/commit handled automatically at method exit
    }
}

✅ No need for sessionFactory.openSession(), beginTransaction(), commit(), or close() — Spring Boot handles it transparently.

🔹 How is this possible?

• Spring Boot configures a JpaTransactionManager (or HibernateTransactionManager) that creates and manages the Hibernate session based on your @Transactional boundaries.
• Sessions are usually scoped to the transaction — so each @Transactional method gets its own session.

🔹 When might you manually open a session?

• Rare advanced scenarios, like:
  • Using a StatelessSession for bulk operations.
  • Writing a custom repository implementation requiring low-level Hibernate features.
  • Managing multiple sessions explicitly (multi-tenancy, special batch processes).

But 99% of the time, you should let Spring manage it, especially in CRUD or business service layers.

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✅ Key takeaway:
In Spring Boot apps, you don’t need to manually open or close Hibernate sessions — simply use @Transactional, and Spring will handle session management, transaction boundaries, and resource cleanup automatically.