Session and SessionFactory

• The SessionFactory and Session are fundamental components in Hibernate’s architecture.

• SessionFactory is a thread-safe, immutable object that serves as a factory for Session instances and caches compiled mappings.

• Session represents a single unit of work and maintains a persistence context with first-level caching.

SessionFactory Internals

public class HibernateUtil {
    private static final SessionFactory sessionFactory = buildSessionFactory();

    private static SessionFactory buildSessionFactory() {
        try {
            // Create SessionFactory from hibernate.cfg.xml
            return new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public static void shutdown() {
        getSessionFactory().close();
    }
}

Session Lifecycle

Session session = null;
Transaction transaction = null;

try {
    session = HibernateUtil.getSessionFactory().openSession();
    transaction = session.beginTransaction();

    // Perform database operations

    transaction.commit();
} catch (Exception e) {
    if (transaction != null) transaction.rollback();
    e.printStackTrace();
} finally {
    if (session != null) session.close();
}

Session States

• Transient: Object created but not associated with session
• Persistent: Object associated with session and saved in database
• Detached: Object was persistent but session closed
• Removed: Object scheduled for deletion