Java.Hibernate.Beginner.How do you close a Hibernate session?

You close a Hibernate Session by calling its close() method:

session.close();

🔹 What happens when you call session.close()?
✅ Releases the JDBC connection associated with the session back to the connection pool (e.g., HikariCP).
✅ Destroys the session’s first-level cache, evicting all managed entities.
✅ Cleans up other resources like prepared statements and internal caches.
✅ Marks the session as closed — trying to use it afterward will throw a org.hibernate.SessionException.

🔹 When should you close a session?

• Always close the session after finishing a unit of work (e.g., at the end of a request or service method).
• If you don’t close it, you can leak database connections, exhaust the connection pool, or hold unnecessary memory.

🔹 Full example with proper session closure:

Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

try {
    User user = session.get(User.class, 1L);
    user.setUsername("updated_name");

    tx.commit();
} catch (Exception e) {
    if (tx != null) tx.rollback();
    e.printStackTrace();
} finally {
    session.close(); // ensures session is closed even if exceptions occur
}

🔹 In Spring Boot apps:
✅ You typically don’t call session.close() manually → Spring manages session lifecycle automatically when you use @Transactional.

Always call session.close() when done to release database resources — in modern apps, Spring or other frameworks often handle this for you, but in manual setups it’s your responsibility.