[Springboot] 20 댓글 이어서 ( 깊은 복사, DTO를 만드는 이유 )

{{>layout/header}}

<div class="container p-5">

    <!-- 수정삭제버튼 -->
        <div class="d-flex justify-content-end">
            <a href="/api/board/{{model.id}}/update-form" class="btn btn-warning me-1">수정</a>
            <form action="/api/board/{{model.id}}/delete" method="post">
                <button class="btn btn-danger">삭제</button>
            </form>
        </div>

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

    <!-- 게시글내용 -->
    <div>
        <h2><b>{{model.title}}</b></h2>
        <hr/>
        <div class="m-4 p-2">
            {{{model.content}}}
        </div>
    </div>
    <!-- 댓글 -->
    <div class="card mt-3">
        <!-- 댓글등록 -->
        <div class="card-body">
            <form action="/reply/save" method="post">
                <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">
            {{#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-primary text-white rounded">{{user.username}}</div>
                    <div>{{comment}}</div>
                </div>

                <form action="#" method="post">
                    <button class="btn">🗑</button>
                </form>

            </div>
            {{/model.replies}}

        </div>
    </div>

</div>

{{>layout/footer}}

1. 템플릿 엔진 (JSP) 왜 X ?

1. DTO 사용 이유
1. 프론트엔드 ORM
2. 프론트엔드 정확

SELECT bt.id, bt.title, bt.content, ut.username, rt.comment, rut.username
FROM board_tb bt
INNER JOIN user_tb ut ON bt.user_id = ut.id
LEFT OUTER JOIN reply_tb rt on bt.id = rt.board_id
LEFT OUTER JOIN user_tb rut on rut.id = rt.user_id
where bt.id = 5;

package org.example.springv3.board;

import lombok.Data;
import org.example.springv3.reply.Reply;
import org.example.springv3.user.User;

import java.util.ArrayList;
import java.util.List;

public class BoardResponse {

    @Data
    public static class DetailDTO {

        private Integer id;
        private String title;
        private String content;
        private Boolean isOwner;
        private Integer userId;
        private String username;

        // 댓글들
        // 여기 엔티티 넣으면 나중에 레이지 로딩이 발생한다. (-> 오픈인뷰 때문에 )
        // 똑같이 생긴 dto를 만들어서 넣어라. (-> 비영속객체를 만들어서 응답하는게 낫다 )
        private List<ReplyDTO> replies = new ArrayList<>();

        public DetailDTO(Board board, User sessionUser) {
            this.id = board.getId();
            this.title = board.getTitle();
            this.content = board.getContent();
            this.isOwner = false;

            if (sessionUser != null) {
                if (board.getUser().getId() == sessionUser.getId()) {
                    isOwner = true; // 권한체크

                }
            }

            this.userId = board.getUser().getId();
            this.username = board.getUser().getUsername();

            for(Reply reply : board.getReplies()){
                replies.add(new ReplyDTO(reply, sessionUser));
            }
        }

        @Data
        public class ReplyDTO{
            private Integer id;
            private String comment;
            private String username;
            private Boolean isOwner;

            public ReplyDTO(Reply reply, User sessionUser) {
                this.id = reply.getId();
                this.comment = reply.getComment();
                this.username = reply.getUser().getUsername();
                this.isOwner = false;

                if (sessionUser != null) {
                    if (reply.getUser().getId() == sessionUser.getId()) {
                        isOwner = true; // 권한체크

                    }
                }
            }
        }
    }
}

    @GetMapping("/v3/board/{id}")
    public @ResponseBody Board detailV3(@PathVariable("id") Integer id) {
        User sessionUser = (User) session.getAttribute("sessionUser");

        Board model = boardService.게시글상세보기V3(sessionUser, id);

        return model;
    }

    public Board 게시글상세보기V3(User sessionUser, Integer boardId){
        Board boardPS = boardRepository.mFindByIdWithReply(boardId)
                .orElseThrow(() -> new Exception404("게시글이 없습니다."));
        return boardPS;
    }

alert('Could not write JSON: Document nesting depth (1001) exceeds the maximum allowed (1000, from `StreamWriteConstraints.getMaxNestingDepth()`)');
    history.back();

1. getUser하는 순간 JPA가 select 먼저 하게 하고 메세지 컨버터가 기다렸다가 Select해서 들고온 값을 가지고 뷰에 가게 순서 정해주기.

2. 엔티티로 return 하지말고 dto를 만들어서 return 하면 레이지 로딩이고, 메세지컨버터 순서정해주고 나발이고 신경 안써도 된다.