41. 좋아요 구현 : 목록 만들기

1. detail.mustache에서 디자인 만들기

{{> layout/header}}

<div class="container p-5">
    {{#board.boardOwner}}
        <!-- 수정삭제버튼 -->
        <div class="d-flex justify-content-end">
            <a href="/board/{{board.id}}/updateForm" class="btn btn-warning me-1">수정</a>
            <form action="/board/{{board.id}}/delete" method="post">
                <button class="btn btn-danger">삭제</button>
            </form>
        </div>
    {{/board.boardOwner}}

    <div class="d-flex justify-content-end">
        <b>작성자</b> :  {{board.username}}
    </div>

    <!-- 게시글내용 -->
    <div>
        <h2><b>{{board.title}}</b></h2>
        <hr/>
        <div class="m-4 p-2">
            {{board.content}}
        </div>
    </div>

    <!-- 좋아요 / 따로 조회해서 들고오기-->
    <div>
        <i class="far fa-heart my-cursor"></i>  <span>10</span>
    </div>

    <!-- 댓글 -->
    <div class="card mt-3">
        <!-- 댓글등록 -->
        <div class="card-body">
            <form action="/reply/save" method="post">
                <input type="hidden" name="boardId" value="{{board.id}}">
                <textarea class="form-control" rows="2" name="comment"></textarea>
                <div class="d-flex justify-content-end">
                    <button type="submit" class="btn btn-outline-primary mt-1">댓글등록</button>
                </div>
            </form>
        </div>

        <!-- 댓글목록 -->
        <div class="card-footer">
            <b>댓글리스트</b>
        </div>
        <div class="list-group">
            {{#replyList}}
                <!-- 댓글아이템 -->
                <div class="list-group-item d-flex justify-content-between align-items-center">
                    <div class="d-flex">
                        <div class="px-1 me-1 bg-primary text-white rounded">{{username}}</div>
                        <div>{{comment}}</div>
                    </div>
                    {{#replyOwner}}
                        <form action="/reply/{{id}}/delete" method="post">
                            <button class="btn">🗑</button>
                        </form>
                    {{/replyOwner}}
                </div>
            {{/replyList}}
        </div>
    </div>
</div>

{{> layout/footer}}

2. love 테이블 관계

• 관계 : N:N

• 외래키 두 개가 필요함 : user_id, board_id

• 필요한 것 : user_id, board_id가 중복될 수 없음

3. love 패키지 만들어서 Love 클래스 만들기

• love_tb 만들기

package shop.mtcoding.blog.love;

import jakarta.persistence.*;
import lombok.Data;
import java.sql.Timestamp;

@Table(name="love_tb")
@Data
@Entity // 테이블 생성하기 위해 필요한 어노테이션
public class Love {
    @Id // PK 설정
    @GeneratedValue(strategy = GenerationType.IDENTITY) // auto_increment 전략
    private Integer id;
    private Integer boardId;
    private Integer userId;
    private Timestamp createdAt;
}

• 확인하기

4. 더미 데이터 추가하기

• data.sql에서 추가하기

insert into user_tb(username, password, email, created_at) values('ssar', '1234', 'ssar@nate.com', now());
insert into user_tb(username, password, email, created_at) values('cos', '1234', 'cos@nate.com', now());

insert into board_tb(title, content, user_id, created_at) values('제목1', '내용1', 1, now());
insert into board_tb(title, content, user_id, created_at) values('제목2', '내용2', 1, now());
insert into board_tb(title, content, user_id, created_at) values('제목3', '내용3', 1, now());
insert into board_tb(title, content, user_id, created_at) values('제목4', '내용4', 2, now());
insert into board_tb(title, content, user_id, created_at) values('title5', '내용5', 2, now());
insert into board_tb(title, content, user_id, created_at) values('title6', '내용6', 2, now());
insert into board_tb(title, content, user_id, created_at) values('title7', '내용7', 2, now());
insert into board_tb(title, content, user_id, created_at) values('title8', '내용8', 2, now());
insert into board_tb(title, content, user_id, created_at) values('title9', '내용9', 2, now());

insert into reply_tb(comment, board_id, user_id, created_at) values('댓글1', 1, 1, now());
insert into reply_tb(comment, board_id, user_id, created_at) values('댓글2', 4, 1, now());
insert into reply_tb(comment, board_id, user_id, created_at) values('댓글3', 4, 1, now());
insert into reply_tb(comment, board_id, user_id, created_at) values('댓글4', 4, 2, now());

insert into love_tb(board_id, user_id, created_at) values(9, 1, now());
insert into love_tb(board_id, user_id, created_at) values(9, 2, now());
insert into love_tb(board_id, user_id, created_at) values(8, 2, now());

5. 좋아요 로직 구현하기

• isLove = true일 때 → fas heart와 빨간색으로 바뀌게 하기

• isLove = false일 때 → 좋아요 안 누른 상태

{{> layout/header}}

<div class="container p-5">
    {{#board.boardOwner}}
        <!-- 수정삭제버튼 -->
        <div class="d-flex justify-content-end">
            <a href="/board/{{board.id}}/updateForm" class="btn btn-warning me-1">수정</a>
            <form action="/board/{{board.id}}/delete" method="post">
                <button class="btn btn-danger">삭제</button>
            </form>
        </div>
    {{/board.boardOwner}}

    <div class="d-flex justify-content-end">
        <b>작성자</b> :  {{board.username}}
    </div>

    <!-- 게시글내용 -->
    <div>
        <h2><b>{{board.title}}</b></h2>
        <hr/>
        <div class="m-4 p-2">
            {{board.content}}
        </div>
    </div>

    <!-- 좋아요 / 따로 조회해서 들고오기-->
    <div>
        <i class="far fa-heart my-cursor"></i> <span>10</span>
        <i class="fas fa-heart my-cursor text-danger"></i> <span>5</span>
    </div>

    <!-- 댓글 -->
    <div class="card mt-3">
        <!-- 댓글등록 -->
        <div class="card-body">
            <form action="/reply/save" method="post">
                <input type="hidden" name="boardId" value="{{board.id}}">
                <textarea class="form-control" rows="2" name="comment"></textarea>
                <div class="d-flex justify-content-end">
                    <button type="submit" class="btn btn-outline-primary mt-1">댓글등록</button>
                </div>
            </form>
        </div>

        <!-- 댓글목록 -->
        <div class="card-footer">
            <b>댓글리스트</b>
        </div>
        <div class="list-group">
            {{#replyList}}
                <!-- 댓글아이템 -->
                <div class="list-group-item d-flex justify-content-between align-items-center">
                    <div class="d-flex">
                        <div class="px-1 me-1 bg-primary text-white rounded">{{username}}</div>
                        <div>{{comment}}</div>
                    </div>
                    {{#replyOwner}}
                        <form action="/reply/{{id}}/delete" method="post">
                            <button class="btn">🗑</button>
                        </form>
                    {{/replyOwner}}
                </div>
            {{/replyList}}
        </div>
    </div>
</div>

{{> layout/footer}}

• 좋아요 부분 머스태치 분법으로 설정하기

{{> layout/header}}

<div class="container p-5">
    {{#board.boardOwner}}
        <!-- 수정삭제버튼 -->
        <div class="d-flex justify-content-end">
            <a href="/board/{{board.id}}/updateForm" class="btn btn-warning me-1">수정</a>
            <form action="/board/{{board.id}}/delete" method="post">
                <button class="btn btn-danger">삭제</button>
            </form>
        </div>
    {{/board.boardOwner}}

    <div class="d-flex justify-content-end">
        <b>작성자</b> :  {{board.username}}
    </div>

    <!-- 게시글내용 -->
    <div>
        <h2><b>{{board.title}}</b></h2>
        <hr/>
        <div class="m-4 p-2">
            {{board.content}}
        </div>
    </div>

    <!-- 좋아요 / 따로 조회해서 들고오기-->
    <div>
        {{#isLove}}
            <i class="fas fa-heart my-cursor text-danger"></i> <span>5</span>
        {{/isLove}}

        {{^isLove}}
        <i class="far fa-heart my-cursor"></i> <span>10</span>
        {{/isLove}}
    </div>

    <!-- 댓글 -->
    <div class="card mt-3">
        <!-- 댓글등록 -->
        <div class="card-body">
            <form action="/reply/save" method="post">
                <input type="hidden" name="boardId" value="{{board.id}}">
                <textarea class="form-control" rows="2" name="comment"></textarea>
                <div class="d-flex justify-content-end">
                    <button type="submit" class="btn btn-outline-primary mt-1">댓글등록</button>
                </div>
            </form>
        </div>

        <!-- 댓글목록 -->
        <div class="card-footer">
            <b>댓글리스트</b>
        </div>
        <div class="list-group">
            {{#replyList}}
                <!-- 댓글아이템 -->
                <div class="list-group-item d-flex justify-content-between align-items-center">
                    <div class="d-flex">
                        <div class="px-1 me-1 bg-primary text-white rounded">{{username}}</div>
                        <div>{{comment}}</div>
                    </div>
                    {{#replyOwner}}
                        <form action="/reply/{{id}}/delete" method="post">
                            <button class="btn">🗑</button>
                        </form>
                    {{/replyOwner}}
                </div>
            {{/replyList}}
        </div>
    </div>
</div>

{{> layout/footer}}

6. /board/{id}에서 설정하기

package shop.mtcoding.blog.board;

import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpSession;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import shop.mtcoding.blog.reply.ReplyRepository;
import shop.mtcoding.blog.user.User;

import java.util.List;

@RequiredArgsConstructor
@Controller
public class BoardController {

    private final HttpSession session; // DI
    private final BoardRepository boardRepository; // DI
    private final ReplyRepository replyRepository;

    // ?title=제목1&content=내용1
    // title=제목1&content=내용1
    // 쿼리 스트링과 -x-www-form-urlencoded와 파싱 방법이 동일함
    @PostMapping("/board/{id}/update")
    public String update(@PathVariable int id, BoardRequest.UpdateDTO requestDTO) { // 파싱 전략이 json으로 바뀜
        // System.out.println(requestDTO); 정보 받기 확인

        // 인증 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 권한 체크하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            return "error/403";
        }

        // update board_tb set title =?, content =?, where id =?
        boardRepository.update(requestDTO, id);
        return "redirect:/board/" + id; // 수정한 게시글로 돌아가기
    }

    @GetMapping("/board/{id}/updateForm") // 보드에 해당 페이지
    public String updateFormn(@PathVariable int id, HttpServletRequest request) {

        // 인증 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 권한 체크하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            request.setAttribute("status", 403);
            request.setAttribute("msg", "게시글을 수정할 권한이 없습니다");
            return "error/40x"; // 리다이렉트 하면 데이터 사라지니까 하면 안됨
        }
        // 가방에 담기
        request.setAttribute("board", board);

        return "board/updateForm";
    }

    @PostMapping("/board/{id}/delete") // body데이터가 없어서 유효성 검사 안해도 됨
    public String delete(@PathVariable int id) {
        // 1. 인증 검사하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }
        // 2. 권한 검사하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            return "error/403";
        }
        boardRepository.deleteById(id);

        return "redirect:/";
    }

    @PostMapping("/board/save")
    public String save(BoardRequest.SaveDTO requestDTO, HttpServletRequest request) {
        // 1. 인증 체크
        User sessionUser = (User) session.getAttribute("sessionUser");
        System.out.println("sessionUser:" + sessionUser);
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 2. 바디 데이터 확인 및 유효성 검사
        System.out.println(requestDTO);

        if (requestDTO.getTitle().length() > 30) {
            request.setAttribute("status", 400);
            request.setAttribute("msg", "title의 길이가 30자를 초과해서는 안되요");
            return "error/40x"; // BadRequest
        }

        // 3. 모델 위임
        // insert into board_tb(title, content, user_id, created_at) values(?,?,?, now());
        boardRepository.save(requestDTO, sessionUser.getId());

        return "redirect:/";
    }

    // http://localhost:8080?page=0 쿼리스트링
    // 스프링에서 쿼리 스트링 받는 방법은 매개 변수에 받기
    @GetMapping({"/"})
    public String index(HttpServletRequest request,
                        @RequestParam(defaultValue = "0") Integer page,
                        @RequestParam(defaultValue = "") String keyword) {
        // isEmpty : 공백, null
        // isBlank : 공백, null, 화이트 space(눈에 안보이는 공백)
        if (keyword.isBlank()) {
            List<Board> boardList = boardRepository.findAll(page);
            // 전체 페이지 개수
            int count = boardRepository.count().intValue();

            int namerge = count % 3 == 0 ? 0 : 1;
            int allPageCount = count / 3 + namerge;

            request.setAttribute("boardList", boardList);
            request.setAttribute("first", page == 0);
            request.setAttribute("last", allPageCount == page + 1);
            request.setAttribute("prev", page - 1);
            request.setAttribute("next", page + 1);
            request.setAttribute("keyword", "");
        } else {
            List<Board> boardList = boardRepository.findAll(page, keyword);
            // 전체 페이지 개수
            int count = boardRepository.count(keyword).intValue();

            int namerge = count % 3 == 0 ? 0 : 1;
            int allPageCount = count / 3 + namerge;

            request.setAttribute("boardList", boardList);
            request.setAttribute("first", page == 0);
            request.setAttribute("last", allPageCount == page + 1);
            request.setAttribute("prev", page - 1);
            request.setAttribute("next", page + 1);
            request.setAttribute("keyword", keyword);
        }
        return "index";
    }

    @GetMapping("/board/saveForm") // /board/saveForm Get요청이 옴
    public String saveForm() { // session 영역에 접근하기 위한
        // 1. session 영역에 sessionUser 키 값에 user 객체가 있는지 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");

        // 2. 값이 null이면 로그인 페이지로 리다이렉션
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }
        // 3. null이 아니면 /board/saveForm으로 이동
        return "board/saveForm";
    }

    // 상세보기시 호출
    @GetMapping("/board/{id}") // 1이 프라이머리키 -> 뭐든 넣어도 실행시키려면 변수화시켜서 {}
    public String detail(@PathVariable int id, HttpServletRequest request) {
        User sessionUser = (User) session.getAttribute("sessionUser"); // 페이지 권한

        BoardResponse.DetailDTO boardDTO = boardRepository.findByIdWithUser(id); //메서드 이름 변경
        boardDTO.isBoardOwner(sessionUser); // null이면 터짐

        List<BoardResponse.ReplyDTO> replyDTOList = replyRepository.findByBoardId(id, sessionUser);

        request.setAttribute("board", boardDTO);
        request.setAttribute("replyList", replyDTOList);
        request.setAttribute("isLove", true);
        request.setAttribute("loveCount", 2);

        return "board/detail";
    }
}

7. BoardRepository에서 save(), deleteById() 외 다 지우기

package shop.mtcoding.blog.board;

import jakarta.persistence.EntityManager;
import jakarta.persistence.Query;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

@RequiredArgsConstructor
@Repository
public class BoardRepository {
    private final EntityManager em;

    @Transactional
    public void save(BoardRequest.SaveDTO requestDTO, int userId) {
        Query query = em.createNativeQuery("insert into board_tb(title, content, user_id, created_at) values(?,?,?, now())");
        query.setParameter(1, requestDTO.getTitle());
        query.setParameter(2, requestDTO.getContent());
        query.setParameter(3, userId);

        query.executeUpdate();
    }

    @Transactional
    public void deleteById(int id) {
        Query query = em.createNativeQuery("delete from board_tb where id = ?");
        query.setParameter(1, id);
        query.executeUpdate();
    }
}

8. H2에서 쿼리 테스트하기

SELECT * FROM LOVE_TB;

select count(*) from love_tb where board_id=9;

select *from love_tb where board_id=9;

select id, user_id from love_tb where board_id=9 and user_id=1;
select id, user_id from love_tb where board_id=8 and user_id=1;

select user_id from love_tb where board_id=8 and user_id=1;

• 서브 쿼리 사용하기

select 
id,
user_id,
(select count(*) from love_tb where board_id=9) loveCount
from love_tb where board_id=9 and user_id=1;

• isLove를 true/false로 나타내기

SELECT 
    id, 
    CASE 
        WHEN user_id IS NULL THEN FALSE 
        ELSE TRUE 
    END AS isLove,
    (SELECT COUNT(*) FROM love_tb WHERE board_id = 9) AS loveCount 
FROM 
    love_tb 
WHERE 
    board_id = 9 AND user_id = 1;

SELECT 
    id, 
    CASE 
        WHEN user_id IS NULL THEN FALSE 
        ELSE TRUE 
    END AS isLove,
    (SELECT COUNT(*) FROM love_tb WHERE board_id = 9) AS loveCount 
FROM 
    love_tb 
WHERE 
    board_id = 9 AND user_id = 2;


SELECT 
    id, 
    CASE 
        WHEN user_id IS NULL THEN FALSE 
        ELSE TRUE 
    END AS isLove,
    (SELECT COUNT(*) FROM love_tb WHERE board_id = 9) AS loveCount 
FROM 
    love_tb 
WHERE 
    board_id = 9 AND user_id = 3;

9. entuty를 받을 수 있는 DTO 만들기

package shop.mtcoding.blog.love;

import lombok.AllArgsConstructor;
import lombok.Data;

public class LoveResponse {

    @AllArgsConstructor
    @Data
    public static class DetailDTO {
        private Integer id;
        private Boolean isLove;
        private Long loveCount;
    }
}

• 결과는 무조건 1개

• 복합키 걸어야 함

@Table(name ="", uniqueConstraints = { // 복합키 만들기
        @UniqueConstraint(
                name="NAME_AGE_UNIQUE",
                columnNames={"NAME","AGE"}
        )})

package shop.mtcoding.blog.love;

import jakarta.persistence.*;
import lombok.Data;

import java.sql.Timestamp;

@Table(name = "love_tb", uniqueConstraints = { // 복합키 만들기
        @UniqueConstraint(
                name = "love_uk",
                columnNames = {"board_id", "user_id"} // 컬럼명 적어주기
        )})
@Data
@Entity // 테이블 생성하기 위해 필요한 어노테이션
public class Love {
    @Id // PK 설정
    @GeneratedValue(strategy = GenerationType.IDENTITY) // auto_increment 전략
    private Integer id;
    private Integer boardId;
    private Integer userId;
    private Timestamp createdAt;
}

• 확인하기

10. LoveRepository에 findLove() 만들기

package shop.mtcoding.blog.love;

import jakarta.persistence.EntityManager;
import jakarta.persistence.Query;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Repository;

@RequiredArgsConstructor
@Repository
public class LoveRepository {
    private final EntityManager em;

    public LoveResponse.DetailDTO findLove(int boardId, int sessionUserId){
        String q = """
                SELECT
                    id,
                    CASE
                        WHEN user_id IS NULL THEN FALSE
                        ELSE TRUE
                    END AS isLove,
                    (SELECT COUNT(*) FROM love_tb WHERE board_id = ?) AS loveCount
                FROM
                    love_tb
                WHERE
                    board_id = ? AND user_id = ?;
                """;
        Query query = em.createNativeQuery(q);
        query.setParameter(1, boardId);
        query.setParameter(2, boardId);
        query.setParameter(3, sessionUserId);

        Object[] row = (Object[]) query.getSingleResult();
        Integer id = (Integer) row[0];
        Boolean isLove = (Boolean) row[1];
        Long loveCount = (Long) row[2];

        System.out.println("id : "+id);
        System.out.println("isLove : "+isLove);
        System.out.println("loveCount : "+loveCount);

        LoveResponse.DetailDTO responseDTO = new LoveResponse.DetailDTO(
                id, isLove, loveCount
        );
        return responseDTO;
    }
}

• test하기

package shop.mtcoding.blog.love;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.context.annotation.Import;

@Import(LoveRepository.class)
@DataJpaTest
public class LoveRepositoryTest {

    @Autowired
    private LoveRepository loveRepository;

    @Test
    public void findLove_test() {
        // given
        int boardId = 9;
        int sessionUserId = 1;

        // when
        loveRepository.findLove(boardId, sessionUserId);
    }
}

package shop.mtcoding.blog.board;

import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpSession;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import shop.mtcoding.blog.love.LoveRepository;
import shop.mtcoding.blog.love.LoveResponse;
import shop.mtcoding.blog.reply.ReplyRepository;
import shop.mtcoding.blog.user.User;

import java.util.List;

@RequiredArgsConstructor
@Controller
public class BoardController {

    private final HttpSession session; // DI
    private final BoardRepository boardRepository; // DI
    private final ReplyRepository replyRepository;
    private final LoveRepository loveRepository;

    // ?title=제목1&content=내용1
    // title=제목1&content=내용1
    // 쿼리 스트링과 -x-www-form-urlencoded와 파싱 방법이 동일함
    @PostMapping("/board/{id}/update")
    public String update(@PathVariable int id, BoardRequest.UpdateDTO requestDTO) { // 파싱 전략이 json으로 바뀜
        // System.out.println(requestDTO); 정보 받기 확인

        // 인증 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 권한 체크하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            return "error/403";
        }

        // update board_tb set title =?, content =?, where id =?
        boardRepository.update(requestDTO, id);
        return "redirect:/board/" + id; // 수정한 게시글로 돌아가기
    }

    @GetMapping("/board/{id}/updateForm") // 보드에 해당 페이지
    public String updateFormn(@PathVariable int id, HttpServletRequest request) {

        // 인증 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 권한 체크하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            request.setAttribute("status", 403);
            request.setAttribute("msg", "게시글을 수정할 권한이 없습니다");
            return "error/40x"; // 리다이렉트 하면 데이터 사라지니까 하면 안됨
        }
        // 가방에 담기
        request.setAttribute("board", board);

        return "board/updateForm";
    }

    @PostMapping("/board/{id}/delete") // body데이터가 없어서 유효성 검사 안해도 됨
    public String delete(@PathVariable int id) {
        // 1. 인증 검사하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }
        // 2. 권한 검사하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            return "error/403";
        }
        boardRepository.deleteById(id);

        return "redirect:/";
    }

    @PostMapping("/board/save")
    public String save(BoardRequest.SaveDTO requestDTO, HttpServletRequest request) {
        // 1. 인증 체크
        User sessionUser = (User) session.getAttribute("sessionUser");
        System.out.println("sessionUser:" + sessionUser);
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 2. 바디 데이터 확인 및 유효성 검사
        System.out.println(requestDTO);

        if (requestDTO.getTitle().length() > 30) {
            request.setAttribute("status", 400);
            request.setAttribute("msg", "title의 길이가 30자를 초과해서는 안되요");
            return "error/40x"; // BadRequest
        }

        // 3. 모델 위임
        // insert into board_tb(title, content, user_id, created_at) values(?,?,?, now());
        boardRepository.save(requestDTO, sessionUser.getId());

        return "redirect:/";
    }

    // http://localhost:8080?page=0 쿼리스트링
    // 스프링에서 쿼리 스트링 받는 방법은 매개 변수에 받기
    @GetMapping({"/"})
    public String index(HttpServletRequest request,
                        @RequestParam(defaultValue = "0") Integer page,
                        @RequestParam(defaultValue = "") String keyword) {
        // isEmpty : 공백, null
        // isBlank : 공백, null, 화이트 space(눈에 안보이는 공백)
        if (keyword.isBlank()) {
            List<Board> boardList = boardRepository.findAll(page);
            // 전체 페이지 개수
            int count = boardRepository.count().intValue();

            int namerge = count % 3 == 0 ? 0 : 1;
            int allPageCount = count / 3 + namerge;

            request.setAttribute("boardList", boardList);
            request.setAttribute("first", page == 0);
            request.setAttribute("last", allPageCount == page + 1);
            request.setAttribute("prev", page - 1);
            request.setAttribute("next", page + 1);
            request.setAttribute("keyword", "");
        } else {
            List<Board> boardList = boardRepository.findAll(page, keyword);
            // 전체 페이지 개수
            int count = boardRepository.count(keyword).intValue();

            int namerge = count % 3 == 0 ? 0 : 1;
            int allPageCount = count / 3 + namerge;

            request.setAttribute("boardList", boardList);
            request.setAttribute("first", page == 0);
            request.setAttribute("last", allPageCount == page + 1);
            request.setAttribute("prev", page - 1);
            request.setAttribute("next", page + 1);
            request.setAttribute("keyword", keyword);
        }
        return "index";
    }

    @GetMapping("/board/saveForm") // /board/saveForm Get요청이 옴
    public String saveForm() { // session 영역에 접근하기 위한
        // 1. session 영역에 sessionUser 키 값에 user 객체가 있는지 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");

        // 2. 값이 null이면 로그인 페이지로 리다이렉션
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }
        // 3. null이 아니면 /board/saveForm으로 이동
        return "board/saveForm";
    }

    // 상세보기시 호출
    @GetMapping("/board/{id}")
    public String detail(@PathVariable int id, HttpServletRequest request) {
        User sessionUser = (User) session.getAttribute("sessionUser");
        BoardResponse.DetailDTO boardDTO = boardRepository.findByIdWithUser(id);
        boardDTO.isBoardOwner(sessionUser);

        List<BoardResponse.ReplyDTO> replyDTOList = replyRepository.findByBoardId(id, sessionUser);
        request.setAttribute("board", boardDTO);
        request.setAttribute("replyList", replyDTOList);

        LoveResponse.DetailDTO loveDetailDTO = loveRepository.findLove(id, sessionUser.getId());
        request.setAttribute("love", loveDetailDTO);
        // fas fa-heart text-danger
        // far fa-heart
        // request.setAttribute("css", "far fa-heart");

        return "board/detail";
    }
}

11. 선택하기 → ajax

• 버튼을 클릭하는 것 : ajax

• 숫자가 바뀌는 것 : csr

• ssr : 리다이렉션, 파일 응답

• csr : 데이터 응답, html을 받으면 전체 새로 고침됨 → 주소가 바뀜

• ajax를 써야하는 경우 : 인증→ 주소가 바뀌지 않음

12. 오류 잡기

• 로그인 안하고 게시글 보기

package shop.mtcoding.blog.board;

import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpSession;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import shop.mtcoding.blog.love.LoveRepository;
import shop.mtcoding.blog.love.LoveResponse;
import shop.mtcoding.blog.reply.ReplyRepository;
import shop.mtcoding.blog.user.User;

import java.util.List;

@RequiredArgsConstructor
@Controller
public class BoardController {

    private final HttpSession session; // DI
    private final BoardRepository boardRepository; // DI
    private final ReplyRepository replyRepository;
    private final LoveRepository loveRepository;

    // ?title=제목1&content=내용1
    // title=제목1&content=내용1
    // 쿼리 스트링과 -x-www-form-urlencoded와 파싱 방법이 동일함
    @PostMapping("/board/{id}/update")
    public String update(@PathVariable int id, BoardRequest.UpdateDTO requestDTO) { // 파싱 전략이 json으로 바뀜
        // System.out.println(requestDTO); 정보 받기 확인

        // 인증 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 권한 체크하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            return "error/403";
        }

        // update board_tb set title =?, content =?, where id =?
        boardRepository.update(requestDTO, id);
        return "redirect:/board/" + id; // 수정한 게시글로 돌아가기
    }

    @GetMapping("/board/{id}/updateForm") // 보드에 해당 페이지
    public String updateFormn(@PathVariable int id, HttpServletRequest request) {

        // 인증 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 권한 체크하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            request.setAttribute("status", 403);
            request.setAttribute("msg", "게시글을 수정할 권한이 없습니다");
            return "error/40x"; // 리다이렉트 하면 데이터 사라지니까 하면 안됨
        }
        // 가방에 담기
        request.setAttribute("board", board);

        return "board/updateForm";
    }

    @PostMapping("/board/{id}/delete") // body데이터가 없어서 유효성 검사 안해도 됨
    public String delete(@PathVariable int id) {
        // 1. 인증 검사하기
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }
        // 2. 권한 검사하기
        Board board = boardRepository.findById(id);
        if (board.getUserId() != sessionUser.getId()) {
            return "error/403";
        }
        boardRepository.deleteById(id);

        return "redirect:/";
    }

    @PostMapping("/board/save")
    public String save(BoardRequest.SaveDTO requestDTO, HttpServletRequest request) {
        // 1. 인증 체크
        User sessionUser = (User) session.getAttribute("sessionUser");
        System.out.println("sessionUser:" + sessionUser);
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }

        // 2. 바디 데이터 확인 및 유효성 검사
        System.out.println(requestDTO);

        if (requestDTO.getTitle().length() > 30) {
            request.setAttribute("status", 400);
            request.setAttribute("msg", "title의 길이가 30자를 초과해서는 안되요");
            return "error/40x"; // BadRequest
        }

        // 3. 모델 위임
        // insert into board_tb(title, content, user_id, created_at) values(?,?,?, now());
        boardRepository.save(requestDTO, sessionUser.getId());

        return "redirect:/";
    }

    // http://localhost:8080?page=0 쿼리스트링
    // 스프링에서 쿼리 스트링 받는 방법은 매개 변수에 받기
    @GetMapping({"/"})
    public String index(HttpServletRequest request,
                        @RequestParam(defaultValue = "0") Integer page,
                        @RequestParam(defaultValue = "") String keyword) {
        // isEmpty : 공백, null
        // isBlank : 공백, null, 화이트 space(눈에 안보이는 공백)
        if (keyword.isBlank()) {
            List<Board> boardList = boardRepository.findAll(page);
            // 전체 페이지 개수
            int count = boardRepository.count().intValue();

            int namerge = count % 3 == 0 ? 0 : 1;
            int allPageCount = count / 3 + namerge;

            request.setAttribute("boardList", boardList);
            request.setAttribute("first", page == 0);
            request.setAttribute("last", allPageCount == page + 1);
            request.setAttribute("prev", page - 1);
            request.setAttribute("next", page + 1);
            request.setAttribute("keyword", "");
        } else {
            List<Board> boardList = boardRepository.findAll(page, keyword);
            // 전체 페이지 개수
            int count = boardRepository.count(keyword).intValue();

            int namerge = count % 3 == 0 ? 0 : 1;
            int allPageCount = count / 3 + namerge;

            request.setAttribute("boardList", boardList);
            request.setAttribute("first", page == 0);
            request.setAttribute("last", allPageCount == page + 1);
            request.setAttribute("prev", page - 1);
            request.setAttribute("next", page + 1);
            request.setAttribute("keyword", keyword);
        }
        return "index";
    }

    @GetMapping("/board/saveForm") // /board/saveForm Get요청이 옴
    public String saveForm() { // session 영역에 접근하기 위한
        // 1. session 영역에 sessionUser 키 값에 user 객체가 있는지 체크하기
        User sessionUser = (User) session.getAttribute("sessionUser");

        // 2. 값이 null이면 로그인 페이지로 리다이렉션
        if (sessionUser == null) {
            return "redirect:/loginForm";
        }
        // 3. null이 아니면 /board/saveForm으로 이동
        return "board/saveForm";
    }

    // 상세보기시 호출
    @GetMapping("/board/{id}")
    public String detail(@PathVariable int id, HttpServletRequest request) {
        User sessionUser = (User) session.getAttribute("sessionUser");
        BoardResponse.DetailDTO boardDTO = boardRepository.findByIdWithUser(id);
        boardDTO.isBoardOwner(sessionUser);

        List<BoardResponse.ReplyDTO> replyDTOList = replyRepository.findByBoardId(id, sessionUser);
        request.setAttribute("board", boardDTO);
        request.setAttribute("replyList", replyDTOList);

        if(sessionUser == null) {
            LoveResponse.DetailDTO loveDetailDTO = loveRepository.findLove(id, 0);
            request.setAttribute("love", loveDetailDTO);
        }else {

        }

        // fas fa-heart text-danger
        // far fa-heart
        // request.setAttribute("css", "far fa-heart");

        return "board/detail";
    }
}

• 아무것도 안나오는 흰 화면

• 오버로딩하기

package shop.mtcoding.blog.love;

import jakarta.persistence.EntityManager;
import jakarta.persistence.Query;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Repository;

@RequiredArgsConstructor
@Repository
public class LoveRepository {
    private final EntityManager em;

    public LoveResponse.DetailDTO findLove(int boardId){ // 오버로딩하기
        String q = """
                SELECT
                    id,
                    CASE
                        false isLove, 
                    (SELECT COUNT(*) FROM love_tb WHERE board_id = ?) AS loveCount
                FROM
                    love_tb
                WHERE
                    board_id = ?;
                """;
        Query query = em.createNativeQuery(q);
        query.setParameter(1, boardId);
        query.setParameter(2, boardId);

        Object[] row = (Object[]) query.getSingleResult();
        Integer id = (Integer) row[0];
        Boolean isLove = (Boolean) row[1];
        Long loveCount = (Long) row[2];

        System.out.println("id : "+id);
        System.out.println("isLove : "+isLove);
        System.out.println("loveCount : "+loveCount);

        LoveResponse.DetailDTO responseDTO = new LoveResponse.DetailDTO(
                id, isLove, loveCount
        );
        return responseDTO;
    }

    public LoveResponse.DetailDTO findLove(int boardId, int sessionUserId){
        String q = """
                SELECT
                    id,
                    CASE
                        WHEN user_id IS NULL THEN FALSE
                        ELSE TRUE
                    END AS isLove,
                    (SELECT COUNT(*) FROM love_tb WHERE board_id = ?) AS loveCount
                FROM
                    love_tb
                WHERE
                    board_id = ? AND user_id = ?;
                """;
        Query query = em.createNativeQuery(q);
        query.setParameter(1, boardId);
        query.setParameter(2, boardId);
        query.setParameter(3, sessionUserId);

        Object[] row = (Object[]) query.getSingleResult();
        Integer id = (Integer) row[0];
        Boolean isLove = (Boolean) row[1];
        Long loveCount = (Long) row[2];

        System.out.println("id : "+id);
        System.out.println("isLove : "+isLove);
        System.out.println("loveCount : "+loveCount);

        LoveResponse.DetailDTO responseDTO = new LoveResponse.DetailDTO(
                id, isLove, loveCount
        );
        return responseDTO;
    }
}

select 0, count(id) loveCount, false isLove
FROM love_tb
WHERE board_id = 9
group by board_id;

• DB에서 안받고 강제로 넣어주기

select count(id) loveCount, false isLove
                FROM love_tb
                WHERE board_id = 9;

package shop.mtcoding.blog.love;

import jakarta.persistence.EntityManager;
import jakarta.persistence.Query;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Repository;

@RequiredArgsConstructor
@Repository
public class LoveRepository {
    private final EntityManager em;

    public LoveResponse.DetailDTO findLove(int boardId) { // 카운트만 받기
        String q = """
                SELECT count(*) loveCount
                FROM love_tb
                WHERE board_id = ?;
                """;
        Query query = em.createNativeQuery(q);
        query.setParameter(1, boardId);

        // 한건만 받을때는 바로 받기
        Long loveCount = (Long) query.getSingleResult();
        Integer id = 0;
        Boolean isLove = false;

        System.out.println("id : " + id);
        System.out.println("isLove : " + isLove);
        System.out.println("loveCount : " + loveCount);

        LoveResponse.DetailDTO responseDTO = new LoveResponse.DetailDTO(
                id, isLove, loveCount
        );
        return responseDTO;
    }

    public LoveResponse.DetailDTO findLove(int boardId, int sessionUserId) {
        String q = """
                SELECT
                    id,
                    CASE
                        WHEN user_id IS NULL THEN FALSE
                        ELSE TRUE
                    END AS isLove,
                    (SELECT COUNT(*) FROM love_tb WHERE board_id = ?) AS loveCount
                FROM
                    love_tb
                WHERE
                    board_id = ? AND user_id = ?;
                """;
        Query query = em.createNativeQuery(q);
        query.setParameter(1, boardId);
        query.setParameter(2, boardId);
        query.setParameter(3, sessionUserId);

        Integer id = null;
        Boolean isLove = null;
        Long loveCount = null;
        try {
            Object[] row = (Object[]) query.getSingleResult();
            id = (Integer) row[0];
            isLove = (Boolean) row[1];
            loveCount = (Long) row[2];
        } catch (Exception e) {
            id = 0;
            isLove = false;
            loveCount = 0L;
        }

        System.out.println("id : " + id);
        System.out.println("isLove : " + isLove);
        System.out.println("loveCount : " + loveCount);

        LoveResponse.DetailDTO responseDTO = new LoveResponse.DetailDTO(
                id, isLove, loveCount
        );
        return responseDTO;
    }
}