[Error] 하이버네이트 @OneToMany 에러 - 2 (해결) (feat. inquery)

1. In query 를 사용했을 때

CinemaRepositoryTest

    @Test
    public void mFindCinemaById_test(){
        Long id = 1L;
        Cinema cinema = cinemaRepository.mFindCinemaById(id); // 여기에 id List로 넣을 수 있다.

        List<Screen> screen1 = cinema.getScreens();
        List<Showtime> showtimes1 = screen1.get(0).getShowtimes(); //screen1.

        //System.out.println(showtimes1.size()); // 이거하면 여기서 lazyLoading 발생
       // System.out.println(showtimes1.getFirst().getId()); // 1
       // System.out.println(showtimes1.getLast().getId()); // 2

        System.out.println("영화관 정보:");
        System.out.println("Cinema ID: " + cinema.getId());
        System.out.println("Cinema Name: " + cinema.getName());

        System.out.println(cinema.getScreens().size()); // 3

        List<Screen> screens = cinema.getScreens();

        List<Long> screenIds = screens.stream().map(screen -> screen.getId()).toList(); // stream -> screen의 id를 배열에 담음
        System.out.println("screenIds : " + screenIds); // [1, 2, 3]
        List<Showtime> showtimes = showtimeRepository.findByScreenIds(screenIds);
        // 상영관들
        for (Screen screen : screens) {
            System.out.println("  Screen ID: " + screen.getId());
            System.out.println("  Screen Name: " + screen.getName());
            System.out.println("  ------------");
            for (Showtime showtime : showtimes) {
                System.out.println("    Showtime ID: " + showtime.getId());
                System.out.println("    상영 시작 시간: " + showtime.getStartedAt());
            }
        }

        }

ShowtimeRepository

package shop.mtcoding.filmtalk.showtime;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;

import java.util.List;
import java.util.Optional;

public interface ShowtimeRepository extends JpaRepository<Showtime,Long> {

    @Query("select st from Showtime st join fetch st.movie m left join fetch st.screen sc where st.id=:id")
    Showtime mFindById(@Param("id") Long id);

    @Query("select s from Showtime s where s.screen.id in :screenIds")
    List<Showtime> findByScreenIds(@Param("screenIds") List<Long> screenIds);

}

CinemaRepository

package shop.mtcoding.filmtalk.cinema;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import java.util.List;
import java.util.Optional;

import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import shop.mtcoding.filmtalk.screen.Screen;

public interface CinemaRepository extends JpaRepository<Cinema, Long> {

    @Query("select c from Cinema c join  fetch c.screens s")
    List<Cinema> mFindAllWithScreen();

    //@Query("SELECT c FROM Cinema c JOIN FETCH c.screens s JOIN FETCH s.showtimes st WHERE c.id = :id")
    @Query("select Distinct c from  Cinema c  join fetch c.screens s where c.id=:id")
    Cinema mFindByIdWithScreen(@Param("id") Long id);


    @Query("select c from  Cinema c  join fetch c.screens s where c.id=:id")
    Cinema mFindCinemaById(@Param("id") Long id);

    @Query("select c from Cinema c join fetch c.region r where c.id=:id")
    Cinema mFindCinemaRegionById(@Param("id") Long id);


}

2. 조인 + 레이지로딩 (Join + LazyLoading) 으로 했을 때