12-1. (실습) 스프링 V3 (댓글)

Feb 24, 2026

1. 테이블 세팅

1) Reply.java

C:\workspace\spring_lab\boardv1\src\main\java\com\example\boardv1\reply\Reply.java


package com.example.boardv1.reply;

import java.time.LocalDateTime;

import org.hibernate.annotations.CreationTimestamp;

import com.example.boardv1.board.Board;
import com.example.boardv1.user.User;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.ManyToOne;
import jakarta.persistence.Table;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * 게시글 1 : 댓글 N
 * 유저 1 : 댓글 N
 */

@NoArgsConstructor
@Data
@Entity
@Table(name = "reply_tb")
public class Reply {
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Id
    private Integer id;
    private String comment;

    @ManyToOne // 디폴트 : EAGER 전략
    private Board board; // board_tb

    @ManyToOne
    private User user;

    @CreationTimestamp
    private LocalDateTime createdAt;
}

2) data.sql - 더미데이터 추가

C:\workspace\spring_lab\boardv1\src\main\resources\db\data.sql


insert into reply_tb (user_id, board_id, comment, created_at) values(1, 6, 'comment1', now());
insert into reply_tb (user_id, board_id, comment, created_at) values(1, 6, 'comment2', now());
insert into reply_tb (user_id, board_id, comment, created_at) values(2, 6, 'comment3', now());
insert into reply_tb (user_id, board_id, comment, created_at) values(1, 5, 'comment4', now());
insert into reply_tb (user_id, board_id, comment, created_at) values(2, 5, 'comment5', now());

2. 댓글 보기

1) ReplyResponse.java

C:\workspace\spring_lab\boardv1\src\main\java\com\example\boardv1\reply\ReplyResponse.java


package com.example.boardv1.reply;

public class ReplyResponse {

    public static class DTO {
        private Integer id;
        private String comment;
        private Integer replyUserId;
        private String replyUsername;
        private boolean isReplyOwner; // 로그인한 유저가 댓글을 작성한 유저인지?

        public DTO(Reply reply, Integer sessionUserId) {
            this.id = reply.getId();
            this.comment = reply.getComment();
            this.replyUserId = reply.getUser().getId();
            this.replyUsername = reply.getUser().getUsername();
            this.isReplyOwner = reply.getUser().getId() == sessionUserId;
        }
    }
    
}

2) BoardResponse.java

C:\workspace\spring_lab\boardv1\src\main\java\com\example\boardv1\board\BoardResponse.java


package com.example.boardv1.board;

import java.util.List;

import com.example.boardv1.reply.ReplyResponse;

import lombok.Data;

public class BoardResponse {

    @Data
    public static class DetailDTO {
        // 화면에 보이지 않는 것 (PK는 화면에 안보여도 무조건 적어야 함!)
        private int id;
        private int userId;

        // 화면에 보이는 것
        private String title;
        private String content;
        private String username;

        // 연산해서 만들어야 되는 것
        private boolean isOwner; // 게시글의 주인인가?

        private List<ReplyResponse.DTO> replies;

        public DetailDTO(Board board, Integer sessionUserId) {
            this.id = board.getId();
            this.userId = board.getUser().getId();
            this.title = board.getTitle();
            this.content = board.getContent();
            this.username = board.getUser().getUsername();
            this.isOwner = board.getUser().getId() == sessionUserId;
            this.replies = board.getReplies().stream()
                    .map(reply -> new ReplyResponse.DTO(reply, sessionUserId))
                    .toList();
        }

    }
}

3) BoardController.java


package com.example.boardv1.board;

import java.util.List;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import com.example.boardv1.user.User;

import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpSession;
import lombok.RequiredArgsConstructor;

@RequiredArgsConstructor // final이 적혀있는 애로 생성자 만들어줌
@Controller // @Controller 적어야 리턴값이 파일이 됨 (외부진입점)
public class BoardController {
    
    private final BoardService boardService;
    private final HttpSession session;

    // title : title=title7&content=content7 (x-www-form)
    @PostMapping("/boards/save")
    public String save(BoardRequest.SaveOrUpdateDTO reqDTO){ // new해서 넣어줌! 필드가 많을 때 상태만 추가하면 되기 때문에 매우 편함! 재사용 가능!(필드명 잘 적어야 함)
        // 인증(v) 권한(x)
        // 인증
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) 
            throw new RuntimeException("인증되지 않았습니다.");

        boardService.게시글쓰기(reqDTO.getTitle(), reqDTO.getContent());
        return "redirect:/"; 
    }

    // body : title=제목&content=내용
    @PostMapping("/boards/{id}/update")
    public String update(@PathVariable("id") int id, BoardRequest.SaveOrUpdateDTO reqDTO){
        // 인증(v) 권한(v)
        // 인증
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) 
            throw new RuntimeException("인증되지 않았습니다.");

        boardService.게시글수정(id,reqDTO.getTitle(), reqDTO.getContent(), sessionUser.getId());
        return "redirect:/boards/"+id; 
    }

    @GetMapping("/")
    public String index(HttpServletRequest req){
        List<Board> list = boardService.게시글목록();
        req.setAttribute("models", list);
        return "index"; 
    }

    @GetMapping("/boards/save-form")
    public String saveForm(){
        // 인증(v) 권한(x)
        // 인증
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) 
            throw new RuntimeException("인증되지 않았습니다.");

        return "board/save-form"; 
    }

    @GetMapping("/boards/{id}/update-form")
    public String updateForm(@PathVariable("id") int id, HttpServletRequest req){
        // 인증(v) 권한(v)
        // 인증
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) 
            throw new RuntimeException("인증되지 않았습니다.");

        Board board = boardService.수정폼게시글정보(id, sessionUser.getId());
        req.setAttribute("model", board);
        return "board/update-form"; 
    }

    @GetMapping("/boards/{id}")
    public String detail(@PathVariable("id") int id, HttpServletRequest req){
        User sessionUser = (User) session.getAttribute("sessionUser"); // Object타입으로 반환하기 때문에 다운캐스팅해야 함
        Integer sessionUserId = sessionUser == null ? null : sessionUser.getId();
        BoardResponse.DetailDTO dto = boardService.상세보기(id, sessionUserId);
        req.setAttribute("model", dto);
        return "board/detail"; // mustache 파일의 경로
    }

    @PostMapping("/boards/{id}/delete")
    public String delete(@PathVariable("id") int id){
        // 인증(v) 권한(v)
        // 인증
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) 
            throw new RuntimeException("인증되지 않았습니다.");

        boardService.게시글삭제(id, sessionUser.getId());
        return "redirect:/"; 
    }

    @GetMapping("/api/boards/{id}")
    public @ResponseBody BoardResponse.DetailDTO apiDetail(@PathVariable("id") int id) {
        User sessionUser = (User) session.getAttribute("sessionUser");
        Integer sessionUserId = sessionUser == null ? null : sessionUser.getId();
        BoardResponse.DetailDTO dto = boardService.상세보기(id, sessionUserId);
        return dto;
    }
}

4) detail.mustache


{{> header}}

<div class="container p-5">

    {{#model.isOwner}}
    <!-- 수정삭제버튼 -->
    <div class="d-flex justify-content-end">
        <a href = "/boards/{{model.id}}/update-form" class="btn btn-secondary me-1">수정</a>
        <form action = "/boards/{{model.id}}/delete" method="post">
            <button class="btn btn-outline-secondary">삭제</button>
        </form>
    </div>
    {{/model.isOwner}}

    <!-- 게시글내용 -->
    <div>
        <h2><b>{{model.title}}</b></h2>
        <hr />
        <div class="d-flex justify-content-end">
            작성자 : {{model.username}}
        </div>
        <div class="m-4 p-2">
            {{model.content}}
        </div>
    </div>

    <!-- 댓글 -->
    <div class="card mt-3">
        <!-- 댓글등록 -->
        <div class="card-body">
            <form action="/replies/save" method="post">
                <textarea class="form-control" rows="2" name="comment"></textarea>
                <div class="d-flex justify-content-end">
                <button class="btn btn-secondary mt-1">                        
                        댓글등록    
                    </button>
                </div>
            </form>
        </div>

        <!-- 댓글목록 -->
        <div class="card-footer">
            <b>댓글리스트</b>
        </div>
        <div class="list-group">
            {{#model.replies}}
                <!-- 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-secondary text-white rounded">{{replyUsername}}</div>
                        <div>{{comment}}</div>
                    </div>
                    {{#isReplyOwner}}
                        <form action="/replies/{{id}}/delete" method="post">
                            <button class="btn">🗑</button>
                        </form>
                    {{/isReplyOwner}}
                </div>
            {{/model.replies}} 
        </div>
    </div>
</div>

</body>
</html>

💡

DTO 만드는 이유(목적)

추가 필드가 필요할 때

필드를 원하는 것만 뽑아서 전달하고 싶을 때

화면에 딱 맞는 데이터를 전달하기 위해

4. 댓글 쓰기

1) ReplyRequest.java


package com.example.boardv1.reply;

import lombok.Data;

public class ReplyRequest {
    
    @Data
    public static class SaveDTO {
        private Integer boardId;
        private String comment;
    }
}

2) ReplyController.java


package com.example.boardv1.reply;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;

import com.example.boardv1.user.User;

import jakarta.servlet.http.HttpSession;
import lombok.RequiredArgsConstructor;

@RequiredArgsConstructor
@Controller
public class ReplyController {

    private final ReplyService replyService;
    private final HttpSession session;

    @PostMapping("/replies/save")
    public String save(ReplyRequest.SaveDTO reqDTO){
        // 인증
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) 
            throw new RuntimeException("인증되지 않았습니다.");

        int sessionUserId = sessionUser.getId();
        replyService.댓글등록(sessionUserId, reqDTO.getBoardId(), reqDTO.getComment());
        return "redirect:/boards/" + reqDTO.getBoardId(); 
    }    
}

3) ReplyService.java


package com.example.boardv1.reply;

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.example.boardv1.board.Board;
import com.example.boardv1.board.BoardRepository;
import com.example.boardv1.user.User;
import com.example.boardv1.user.UserRepository;

import jakarta.persistence.EntityManager;
import lombok.RequiredArgsConstructor;

@RequiredArgsConstructor
@Service
public class ReplyService {

    private final ReplyRepository replyRepository;
    private final EntityManager em;

    @Transactional
    public void 댓글등록(int sessionUserId, int boardId, String comment) {
        Board board = em.getReference(Board.class, boardId); // 가짜로 영속화. 조회하면 계속 쿼리 터지는데 조회 안해도 됨
        User user = em.getReference(User.class, sessionUserId);

        Reply reply = new Reply();
        reply.setBoard(board);
        reply.setUser(user);
        reply.setComment(comment);

        replyRepository.save(reply);
    }
}

4) ReplyRepository.java


package com.example.boardv1.reply;

import java.util.Optional;

import org.springframework.stereotype.Repository;

import jakarta.persistence.EntityManager;
import lombok.RequiredArgsConstructor;

@RequiredArgsConstructor
@Repository
public class ReplyRepository {

    private final EntityManager em;

    public Reply save(Reply reply) {
        em.persist(reply);
        return reply;
    }    
}

5. 댓글 삭제

1) ReplyController.java


package com.example.boardv1.reply;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;

import com.example.boardv1.user.User;

import jakarta.servlet.http.HttpSession;
import lombok.RequiredArgsConstructor;

@RequiredArgsConstructor
@Controller
public class ReplyController {

    private final ReplyService replyService;
    private final HttpSession session;

    // replies/5/delete?boardId=2
    @PostMapping("/replies/{id}/delete")
    public String delete(@PathVariable("id") int id, @RequestParam("boardId") int boardId){
        // 인증
        User sessionUser = (User) session.getAttribute("sessionUser");
        if (sessionUser == null) 
            throw new RuntimeException("인증되지 않았습니다.");

        replyService.댓글삭제(id, sessionUser.getId());

        return "redirect:/boards/" + boardId; 
    }
    
}

2) ReplyService.java


package com.example.boardv1.reply;

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.example.boardv1.board.Board;
import com.example.boardv1.board.BoardRepository;
import com.example.boardv1.user.User;
import com.example.boardv1.user.UserRepository;

import jakarta.persistence.EntityManager;
import lombok.RequiredArgsConstructor;

@RequiredArgsConstructor
@Service
public class ReplyService {

    private final ReplyRepository replyRepository;
    private final EntityManager em;

    @Transactional
    public void 댓글삭제(int id, int sessionUserId) {
        // 영속화(권한체크 하려면 findById해야 함. 권한체크 안해도 되면 getReference사용)
        Reply reply = replyRepository.findById(id)
                .orElseThrow(() -> new RuntimeException("삭제할 댓글을 찾을 수 없어요"));

        // 권한
        if (sessionUserId != reply.getUser().getId())
            throw new RuntimeException("삭제할 권한이 없습니다");

        replyRepository.delete(reply);
    }

}

3) ReplyRepository.java


package com.example.boardv1.reply;

import java.util.Optional;

import org.springframework.stereotype.Repository;

import jakarta.persistence.EntityManager;
import lombok.RequiredArgsConstructor;

@RequiredArgsConstructor
@Repository
public class ReplyRepository {

    private final EntityManager em;

    public Optional<Reply> findById(int id) {
        Reply reply = em.find(Reply.class, id);
        return Optional.ofNullable(reply);
    }

    public Reply save(Reply reply) {
        em.persist(reply);
        return reply;
    }

    public void delete(Reply reply) {
        em.remove(reply);
    }
    
}

4) detail.mustache


{{> header}}

<div class="container p-5">

    {{#model.isOwner}}
    <!-- 수정삭제버튼 -->
    <div class="d-flex justify-content-end">
        <a href = "/boards/{{model.id}}/update-form" class="btn btn-secondary me-1">수정</a>
        <form action = "/boards/{{model.id}}/delete" method="post">
            <button class="btn btn-outline-secondary">삭제</button>
        </form>
    </div>
    {{/model.isOwner}}

    <!-- 게시글내용 -->
    <div>
        <h2><b>{{model.title}}</b></h2>
        <hr />
        <div class="d-flex justify-content-end">
            작성자 : {{model.username}}
        </div>
        <div class="m-4 p-2">
            {{model.content}}
        </div>
    </div>

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

        <!-- 댓글목록 -->
        <div class="card-footer">
            <b>댓글리스트</b>
        </div>
        <div class="list-group">
            {{#model.replies}}
                <!-- 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-secondary text-white rounded">{{replyUsername}}</div>
                        <div>{{comment}}</div>
                    </div>
                    {{#isReplyOwner}}
                        <form action="/replies/{{id}}/delete?boardId={{model.id}}" method="post">
                            <input type="hidden" name="boardId" value="{{model.id}}">
                            <button class="btn">🗑</button>
                        </form>
                    {{/isReplyOwner}}
                </div>
            {{/model.replies}} 
        </div>
    </div>
</div>
</body>
</html>

boardId를 쿼리스트링으로 넘겨주기!

※ 로그인 안 한 상태에서 댓글 입력창 클릭했을 때

1) detail.mustache - 수정

① 코드


{{> header}}

<div class="container p-5">

    {{#model.isOwner}}
    <!-- 수정삭제버튼 -->
    <div class="d-flex justify-content-end">
        <a href = "/boards/{{model.id}}/update-form" class="btn btn-secondary me-1">수정</a>
        <form action = "/boards/{{model.id}}/delete" method="post">
            <button class="btn btn-outline-secondary">삭제</button>
        </form>
    </div>
    {{/model.isOwner}}

    <!-- 게시글내용 -->
    <div>
        <h2><b>{{model.title}}</b></h2>
        <hr />
        <div class="d-flex justify-content-end">
            작성자 : {{model.username}}
        </div>
        <div class="m-4 p-2">
            {{model.content}}
        </div>
    </div>

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

        <!-- 댓글목록 -->
        <div class="card-footer">
            <b>댓글리스트</b>
        </div>
        <div class="list-group">
            {{#model.replies}}
                <!-- 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-secondary text-white rounded">{{replyUsername}}</div>
                        <div>{{comment}}</div>
                    </div>
                    {{#isReplyOwner}}
                        <form action="/replies/{{id}}/delete?boardId={{model.id}}" method="post">
                            <input type="hidden" name="boardId" value="{{model.id}}">
                            <button class="btn">🗑</button>
                        </form>
                    {{/isReplyOwner}}
                </div>
            {{/model.replies}} 
        </div>
    </div>
</div>
{{^sessionUser}}
<script>
    // 1. 조건 (querySelector 사용, textArea에 comment라는 id 하나 추가하기)
    const textArea = document.querySelector("#comment");

    // 2. textArea에 마우스로 클릭했을 때의 이벤트 리스너가 필요함
    textArea.addEventListener("click", function () {

        // 3. 이 때, 행위가 하나 필요함 -> 알림창을 띄워서 '로그인하세요'라고 알려줘야 함
        alert("로그인하세요");
    });
</script>
{{/sessionUser}}
</body>
</html>

② 테스트