mapping 사용법

사용 에디터: VSCode

V6 Flat 버전을 할 때에 mapping에서 toList()가 먹지를 않습니다.

정확한 에러는 toList() 메소드가 없다고 메소드를 만들어 달라고 합니다.

mapping 사용법에는

Map<City, Set<String>> lastNamesByCity

= people.stream().collect(

groupingBy(Person::getCity,

mapping(Person::getLastName,

toSet())));

위와 같이 to타입()으로 쓰는 것 같은데 왜 toList() 타입이 적용 안되는지 모르겠습니다.

OrderApiController

    @GetMapping("/api/v6/orders")
    public List<OrderQueryDto> ordersV6() {
        List<OrderFlatDto> flats = orderQueryRepository.findAllByDto_flat();
   
        return flats.stream()
                .collect(Collectors.groupingBy(o -> new OrderQueryDto(o.getOrderId(), o.getName(), o.getOrderDate(), o.getOrderStatus(), o.getAddress()),
                        Collectors.mapping(o -> new OrderItemQueryDto(o.getOrderId(), o.getItemName(), o.getOrderPrice(), o.getCount()), toList()))).entrySet().stream()
                .map(e -> new OrderQueryDto(e.getKey().getOrderId(), e.getKey().getName(), e.getKey().getOrderDate(), e.getKey().getOrderStatus(), e.getKey().getAddress(), e.getValue()))
                .collect(Collectors.toList());
    }

OrderFlatDto

package jpabook.jpashop.repository.order.query;

import java.time.LocalDateTime;
import jpabook.jpashop.domain.Address;
import jpabook.jpashop.domain.OrderStatus;
import lombok.Data;

@Data
public class OrderFlatDto {
   
    private Long orderId;
    private String name;
    private LocalDateTime orderDate;
    private OrderStatus orderStatus;
    private Address address;
   
    private String itemName;
    private int orderPrice;
    private int count;

    public OrderFlatDto(Long orderId, String name, LocalDateTime orderDate, OrderStatus orderStatus, Address address, String itemName, int orderPrice, int count) {
        this.orderId = orderId;
        this.name = name;
        this.orderDate = orderDate;
        this.orderStatus = orderStatus;
        this.address = address;
        this.itemName = itemName;
        this.orderPrice = orderPrice;
        this.count = count;
    }
}

OrderQueryDto

package jpabook.jpashop.repository.order.query;

import java.time.LocalDateTime;
import java.util.List;

import jpabook.jpashop.domain.Address;
import jpabook.jpashop.domain.OrderStatus;
import lombok.Data;
import lombok.EqualsAndHashCode;

@Data
@EqualsAndHashCode(of = "orderId")
public class OrderQueryDto {
   
    private Long orderId;
    private String name;
    private LocalDateTime orderDate;
    private OrderStatus orderStatus;
    private Address address;
    private List<OrderItemQueryDto> orderItems;

    public OrderQueryDto(Long orderId, String name, LocalDateTime orderDate, OrderStatus orderStatus, Address address) {
        this.orderId = orderId;
        this.name = name;
        this.orderDate = orderDate;
        this.orderStatus = orderStatus;
        this.address = address;
    }

    public OrderQueryDto(Long orderId, String name, LocalDateTime orderDate, OrderStatus orderStatus, Address address, List<OrderItemQueryDto> orderItems) {
        this.orderId = orderId;
        this.name = name;
        this.orderDate = orderDate;
        this.orderStatus = orderStatus;
        this.address = address;
        this.orderItems = orderItems;
    }
}

OrderQueryRepository

    public List<OrderFlatDto> findAllByDto_flat() {
       return em.createQuery("select new jpabook.jpashop.repository.order.query.OrderFlatDto(o.id, m.name, o.orderDate, o.status, d.address, i.name, oi.orderPrice, oi.count)" +
                            " from Order o" +
                            " join o.member m" +
                            " join o.delivery d" +
                            " join o.orderItems oi" +
                            " join oi.item i", OrderFlatDto.class)
                            .getResultList();
  }

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