JPA 소개

spring.datasource.url=jdbc:mysql://localhost:3306/mydb spring.datasource.username=root spring.datasource.password=1234 spring.jpa.hibernate.ddl-auto=update

@Entity public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String name; private String email; }

@Autowired private EntityManagerFactory entityManagerFactory;

EntityManager entityManager = entityManagerFactory.createEntityManager(); entityManager.getTransaction().begin(); User user = new User(); user.setName("John"); user.setEmail("john@example.com"); entityManager.persist(user); entityManager.getTransaction().commit(); entityManager.close();

@PersistenceContext private EntityManager entityManager;

User user = entityManager.find(User.class, 1L); // DB에서 조회 user.setName("Updated Name"); // 값 변경 // 별도의 update 쿼리를 실행하지 않아도 변경이 감지되어 자동 반영됨 entityManager.getTransaction().commit();

@Service public class UserService { @Autowired private EntityManager entityManager; @Transactional public void updateUser(Long id, String newName) { User user = entityManager.find(User.class, id); user.setName(newName); } // 트랜잭션 종료 시 자동으로 변경 사항 반영 }

INSERT INTO user (name, email) VALUES ('John', 'john@example.com'); UPDATE user SET name = 'Updated Name' WHERE id = 1;