SessionFactory and Session

Two Objects, Two Roles

SessionFactory and Session are the two objects you use in almost every Hibernate program. They differ in cost, lifetime, and thread safety.

A Session wraps a JDBC connection and holds the persistence context, which we cover in the next lesson. Never share a session between threads.

Creating and Using Them

SessionFactory sessionFactory = new Configuration()
        .configure()
        .buildSessionFactory();

try (Session session = sessionFactory.openSession()) {
    Student student = session.find(Student.class, 1L);
}

sessionFactory.close();

Code Explanation:

• configure() reads hibernate.cfg.xml from the classpath.
• buildSessionFactory() validates the mappings and prepares Hibernate, so it should run once at startup.
• openSession() returns a new session, and try-with-resources closes it when the block ends.
• find() loads a Student by primary key and returns null if no row exists.
• The factory is closed at application shutdown to release its resources.