import jakarta.persistence.*;
@Entity
@Table(name = "users")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@Column(name = "username")
private String username;
}
EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("persistenceUnitName");
EntityManager entityManager = entityManagerFactory.createEntityManager();
entityManager.getTransaction().begin();
User user = new User();
user.setUsername("Alice");
entityManager.persist(user);
entityManager.getTransaction().commit();
entityManager.close();
EntityManager entityManager = entityManagerFactory.createEntityManager();
TypedQuery<User> query = entityManager.createQuery("SELECT u FROM User u", User.class);
List<User> users = query.getResultList();
entityManager.close();
