메모장- Create,Read 구현하기

• Create 구현

1. 메모 데이터를 저장할 Memo 클래스 생성

package com.sparta.memo.entity;

import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

@Getter
@Setter
@NoArgsConstructor
public class Memo {
    private Long id;
    private String username;
    private String contents;
}

2. 메모 생성하기 API를 받을 수 있는 Controller와 메서드 생성

@RestController
@RequestMapping("/api")
public class MemoController {

    @PostMapping("/memos")
    public MemoResponseDto createMemo(@RequestBody MemoRequestDto requestDto) {
        return null;
    }

}

3. Client에 데이터를 반환할 때 사용할 MemoResponseDto 클래스 생성

package com.sparta.memo.dto;

import lombok.Getter;

@Getter
public class MemoResponseDto {
    private Long id;
    private String username;
    private String contents;
}

4. Client의 요청 데이터를 받아줄 MemoRequestDto 클래스 생성

package com.sparta.memo.dto;

import lombok.Getter;

@Getter
public class MemoRequestDto {
    private String username;
    private String contents;
}

6. 메모 생성 로직 작성

@PostMapping("/memos")
public MemoResponseDto createMemo(@RequestBody MemoRequestDto requestDto) {
    // RequestDto -> Entity
    Memo memo = new Memo(requestDto);

    // Memo Max ID Check
    Long maxId = memoList.size() > 0 ? Collections.max(memoList.keySet()) + 1 : 1;
    memo.setId(maxId);

    // DB 저장
    memoList.put(memo.getId(), memo);

    // Entity -> ResponseDto
    MemoResponseDto memoResponseDto = new MemoResponseDto(memo);
    
    return memoResponseDto;
}

Read 구현

@GetMapping("/memos")
public List<MemoResponseDto> getMemos() {
    // Map To List
    List<MemoResponseDto> responseList = memoList.values().stream()
            .map(MemoResponseDto::new).toList();

    return responseList;
}

MemoController

package com.sparta.memo.controller;

import com.sparta.memo.dto.MemoRequestDto;
import com.sparta.memo.dto.MemoResponseDto;
import com.sparta.memo.entity.Memo;
import org.springframework.web.bind.annotation.*;

import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@RestController
@RequestMapping("/api")
public class MemoController {

    private final Map<Long, Memo> memoList = new HashMap<>();

    @PostMapping("/memos")
    public MemoResponseDto createMemo(@RequestBody MemoRequestDto requestDto) {
        // RequestDto -> Entity
        Memo memo = new Memo(requestDto);

        // Memo Max ID Check
        Long maxId = memoList.size() > 0 ? Collections.max(memoList.keySet()) + 1 : 1;
        memo.setId(maxId);

        // DB 저장
        memoList.put(memo.getId(), memo);

        // Entity -> ResponseDto
        MemoResponseDto memoResponseDto = new MemoResponseDto(memo);

        return memoResponseDto;
    }

    @GetMapping("/memos")
    public List<MemoResponseDto> getMemos() {
        // Map To List
        List<MemoResponseDto> responseList = memoList.values().stream()
                .map(MemoResponseDto::new).toList();

        return responseList;
    }
}