TIL 2023-10-31 JPA 기초

스프링 JPA를 사용하려면 3가지를 만들어야 한다.
첫번째로 Enitity

public class Product extends Timestamped {
		@Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private Long userId;
    private String title;
    private String image;
    private String link;
    private int lprice;
    private int myprice;
}

데이터 베이스 테이블을 매핑해주는 역활을 한다. 엔티티 끼리 연관관계를 설정 할수 있다

@Getter
@Entity
@NoArgsConstructor
public class Member {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
		@Column(nullable = false)
    private String memberName;

    @OneToMany(mappedBy = "member", fetch = FetchType.EAGER)
    private List<Orders> orders = new ArrayList<>();

    public Member(String memberName) {
        this.memberName = memberName;
    }
}

@Getter
@Entity
@NoArgsConstructor
public class Food {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(nullable = false)
    private String foodName;
    @Column(nullable = false)
    private int price;

    @OneToMany(mappedBy = "food",fetch = FetchType.EAGER)
    private List<Orders> orders = new ArrayList<>();

    public Food(String foodName, int price) {
        this.foodName = foodName;
        this.price = price;
    }
}

@Getter
@Entity
@NoArgsConstructor
public class Orders {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne
    @JoinColumn(name = "food_id")
    private Food food;

    @ManyToOne
    @JoinColumn(name = "member_id")
    private Member member;

    public Orders(Food food, Member member) {
        this.food = food;
        this.member = member;
    }
}

두번째로 Repository

public interface MemberRepository extends JpaRepository<Member, Long> {
}

public interface OrdersRepository extends JpaRepository<Orders, Long> {
}

public interface FoodRepository extends JpaRepository<Food, Long> {
}

Repository는 인터페이스로 만들어지며 JpaRepository를 상속받아서 만든다. 간단한 기능들(save(),saveAll(),findAll(),findById()...등)은 자동으로 생성이 된다. 복잡한 기능들은 추가할수 있다.

jpa 추가 기능 구현 공식링크
https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa.query-methods

public interface ProductRepository extends JpaRepository<Product, Long> {
    // (1) 회원 ID 로 등록된 상품들 조회
    List<Product> findAllByUserId(Long userId);

    // (2) 상품명이 title 인 관심상품 1개 조회
		Product findByTitle(String title);

	// (3) 상품명에 word 가 포함된 모든 상품들 조회
		List<Product> findAllByTitleContaining(String word);

		// (4) 최저가가 fromPrice ~ toPrice 인 모든 상품들을 조회
    List<Product> findAllByLpriceBetween(int fromPrice, int toPrice);
}

세번째로 Service

실제로 repository를 활용하는 단계이다

@Component
@RequiredArgsConstructor
public class RestaurantService implements ApplicationRunner {

    private final FoodRepository foodRepository;
    private final OrdersRepository ordersRepository;
    private final MemberRepository memberRepository;

    @Override
    public void run(ApplicationArguments args) throws Exception {

        List<Food> foods = new ArrayList<>();
        Food food1 = new Food("후라이드", 10000);
        foods.add(food1);
        Food food2 = new Food("양념치킨", 12000);
        foods.add(food2);
        Food food3 = new Food("반반치킨", 13000);
        foods.add(food3);
        Food food4 = new Food("고구마피자", 9000);
        foods.add(food4);
        Food food5 = new Food("아보카도피자", 110000);
        foods.add(food5);
        foodRepository.saveAll(foods);

        List<Member> members = new ArrayList<>();
        Member member1 = new Member("삼식이");
        members.add(member1);
        Member member2 = new Member("먹깨비");
        members.add(member2);
        memberRepository.saveAll(members);

        System.out.println("==================================================================");

        System.out.println("Member 데이터");
        List<Member> findMembers = memberRepository.findAll();
        for (Member findMember : findMembers) {
            System.out.println("findMember = " + findMember.getMemberName());
        }

        System.out.println("==================================================================");

        System.out.println("Food 데이터");
        List<Food> findFoods = foodRepository.findAll();
        for (Food findFood : findFoods) {
            System.out.println("findFood = " + findFood.getFoodName());
        }

        List<Orders> ordersList = new ArrayList<>();
        Orders orders1 = new Orders(findFoods.get(0), findMembers.get(0));
        ordersList.add(orders1);
        Orders orders2 = new Orders(findFoods.get(3), findMembers.get(1));
        ordersList.add(orders2);
        Orders orders3 = new Orders(findFoods.get(4), findMembers.get(1));
        ordersList.add(orders3);
        Orders orders4 = new Orders(findFoods.get(2), findMembers.get(0));
        ordersList.add(orders4);
        Orders orders5 = new Orders(findFoods.get(2), findMembers.get(0));
        ordersList.add(orders5);
        Orders orders6 = new Orders(findFoods.get(1), findMembers.get(1));
        ordersList.add(orders6);
        Orders orders7 = new Orders(findFoods.get(1), findMembers.get(0));
        ordersList.add(orders7);
        Orders orders8 = new Orders(findFoods.get(3), findMembers.get(1));
        ordersList.add(orders8);
        ordersRepository.saveAll(ordersList);

        System.out.println("==================================================================");
        int num = 1;

        System.out.println("Orders 데이터");
        List<Orders> orderList = ordersRepository.findAll();

        for (Orders orders : orderList) {
            System.out.println(num);
            System.out.println("주문한 사람 = " + orders.getMember().getMemberName());
            System.out.println("주문한 음식 = " + orders.getFood().getFoodName());
            num++;
        }

        System.out.println("==================================================================");
        System.out.println("삼식이 주문한 음식");
        Member samsik = memberRepository.findById(1L).orElseThrow(
                ()->new RuntimeException("없음")
        );

        num = 1;
        for (Orders orders : samsik.getOrders()) {
            System.out.println(num);
            System.out.println("주문한 음식 = " + orders.getFood().getFoodName());
            System.out.println("주문한 음식 가격 = " + orders.getFood().getPrice());
            num++;
        }


        System.out.println("==================================================================");
        System.out.println("아보카도피자 주문한 사람");
        Food abocado = foodRepository.findById(5L).orElseThrow(
                ()->new RuntimeException("없음")
        );

        for (Orders order : abocado.getOrders()) {
            System.out.println("주문한 사람 = " + order.getMember().getMemberName());
        }


    }
}

간단하게 스프링 JPA를 사용하는 방법을 알아보았다.