자바 ORM 표준 JPA 프로그래밍 실전 예제 4. 상속관계 매핑

요구사항 추가

- Item의 종류는 Album,Book,Movie가 있고 이후에 더 '확장'될 수 있다

- 모든 데이터는 '등록일'과 '수정일'이 필수다

 

@Entity
@Inheritance( strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn( name = "DTYPE")
public abstract class Item extends BaseEntity{

    @Id
    @GeneratedValue
    @Column(name = "ITEM_ID")
    private Long id;

    private String name;
    private int price;
    private int stockQuantity;

    @ManyToMany(mappedBy = "items")
    private List<Category> categories = new ArrayList<>();

@Entity
public class Album extends Item{

    private String artist;

@Entity
public class Book extends Item{

    private String author;
    private String isbn;

@Entity
public class Movie extends Item {

    private String director;
    private String actor;

}

@MappedSuperclass
public class BaseEntity {

    private String createdBy;
    private LocalDate createdDate;
    private String lastModifiedBy;
    private LocalDateTime lastModifiedDate;

public class JpaMain {

    public static void main(String[] args) {

        EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello");

        EntityManager em = emf.createEntityManager();

        EntityTransaction tx = em.getTransaction();

        tx.begin();

        try {

            Book book = new Book();
            book.setName("JPA");
            book.setAuthor("김영한");

            em.persist(book); //Item테이블에 저장된다

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
        } finally {
            em.close();
        }

        emf.close();
    }
}