feat: 특정 다이어리 댓글 전체 조회(커서 기반) API 구현

Author: dnzp75

src/main/java/com/example/log4u/domain/comment/Comment.java

@@ -2,14 +2,18 @@
 
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.DeleteMapping;
+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.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.RestController;
 
+import com.example.log4u.common.dto.PageResponse;
 import com.example.log4u.domain.comment.dto.request.CommentCreateRequestDto;
 import com.example.log4u.domain.comment.dto.response.CommentCreateResponseDto;
+import com.example.log4u.domain.comment.dto.response.CommentResponseDto;
 import com.example.log4u.domain.comment.service.CommentService;
 
 import io.swagger.v3.oas.annotations.tags.Tag;
@@ -39,4 +43,14 @@ public ResponseEntity<Void> deleteComment(@PathVariable Long commentId) {
 		commentService.deleteComment(userId, commentId);
 		return ResponseEntity.noContent().build();
 	}
+
+	@GetMapping("/{diaryId}")
+	public ResponseEntity<PageResponse<CommentResponseDto>> getCommentListByDiary(
+		@PathVariable Long diaryId,
+		@RequestParam(required = false) Long cursorCommentId,
+		@RequestParam(defaultValue = "5") int size
+	) {
+		PageResponse<CommentResponseDto> response = commentService.getCommentListByDiary(diaryId, cursorCommentId, size);
+		return ResponseEntity.ok(response);
+	}
 }

src/main/java/com/example/log4u/domain/comment/controller/CommentController.java

@@ -0,0 +1,15 @@
+package com.example.log4u.domain.comment.dto.response;
+
+import com.example.log4u.domain.comment.entity.Comment;
+
+public record CommentResponseDto(
+	Long commentId,
+	String content
+) {
+	public static CommentResponseDto of(Comment comment) {
+		return new CommentResponseDto(
+			comment.getCommentId(),
+			comment.getContent()
+		);
+	}
+}

src/main/java/com/example/log4u/domain/comment/dto/response/CommentResponseDto.java

@@ -1,9 +1,14 @@
 package com.example.log4u.domain.comment.repository;
 
+import java.time.LocalDateTime;
+import java.util.List;
+
+import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 import com.example.log4u.domain.comment.entity.Comment;
 
-public interface CommentRepository extends JpaRepository<Comment, Long> {
-
+public interface CommentRepository extends JpaRepository<Comment, Long>, CommentRepositoryCustom {
 }

src/main/java/com/example/log4u/domain/comment/repository/CommentRepository.java

@@ -0,0 +1,11 @@
+package com.example.log4u.domain.comment.repository;
+
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Slice;
+
+import com.example.log4u.domain.comment.entity.Comment;
+
+public interface CommentRepositoryCustom {
+
+	Slice<Comment> findByDiaryIdWithCursor(Long diaryId, Long cursorCommentId, Pageable pageable);
+}

src/main/java/com/example/log4u/domain/comment/repository/CommentRepositoryCustom.java

@@ -0,0 +1,40 @@
+package com.example.log4u.domain.comment.repository;
+
+import static com.example.log4u.domain.comment.entity.QComment.*;
+
+import java.util.List;
+
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Slice;
+import org.springframework.data.domain.SliceImpl;
+import org.springframework.stereotype.Repository;
+
+import com.example.log4u.domain.comment.entity.Comment;
+import com.querydsl.jpa.impl.JPAQueryFactory;
+
+import lombok.RequiredArgsConstructor;
+
+@Repository
+@RequiredArgsConstructor
+public class CommentRepositoryImpl implements CommentRepositoryCustom {
+
+	private final JPAQueryFactory queryFactory;
+
+	@Override
+	public Slice<Comment> findByDiaryIdWithCursor(Long diaryId, Long cursorCommentId, Pageable pageable) {
+		List<Comment> result = queryFactory
+			.selectFrom(comment)
+			.where(
+				comment.diaryId.eq(diaryId),
+				cursorCommentId != null ? comment.commentId.lt(cursorCommentId) : null
+			)
+			.orderBy(comment.commentId.desc())
+			.limit(pageable.getPageSize() + 1) // 커서 기반 페이징
+			.fetch();
+
+		boolean hasNext = result.size() > pageable.getPageSize();
+		List<Comment> content = hasNext ? result.subList(0, pageable.getPageSize()) : result;
+
+		return new SliceImpl<>(content, pageable, hasNext);
+	}
+}

src/main/java/com/example/log4u/domain/comment/repository/CommentRepositoryImpl.java

@@ -1,10 +1,18 @@
 package com.example.log4u.domain.comment.service;
 
+import java.util.List;
+
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Slice;
+import org.springframework.data.domain.SliceImpl;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import com.example.log4u.common.dto.PageResponse;
 import com.example.log4u.domain.comment.dto.request.CommentCreateRequestDto;
 import com.example.log4u.domain.comment.dto.response.CommentCreateResponseDto;
+import com.example.log4u.domain.comment.dto.response.CommentResponseDto;
 import com.example.log4u.domain.comment.entity.Comment;
 import com.example.log4u.domain.comment.exception.NotFoundCommentException;
 import com.example.log4u.domain.comment.exception.UnauthorizedAccessException;
@@ -22,7 +30,7 @@ public class CommentService {
 
 	@Transactional
 	public CommentCreateResponseDto addComment(Long userId, CommentCreateRequestDto requestDto) {
-		checkDiaryExists(requestDto);
+		checkDiaryExists(requestDto.diaryId());
 		Comment comment = requestDto.toEntity(userId);
 		commentRepository.save(comment);
 		return CommentCreateResponseDto.of(comment);
@@ -35,8 +43,8 @@ public void deleteComment(Long userId, Long commentId) {
 		commentRepository.delete(comment);
 	}
 
-	private void checkDiaryExists(CommentCreateRequestDto requestDto) {
-		diaryService.checkDiaryExists(requestDto.diaryId());
+	private void checkDiaryExists(Long diaryId) {
+		diaryService.checkDiaryExists(diaryId);
 	}
 
 	private void validateCommentOwner(Long userId, Comment comment) {
@@ -49,4 +57,18 @@ private Comment getComment(Long commentId) {
 		return commentRepository.findById(commentId)
 			.orElseThrow(NotFoundCommentException::new);
 	}
+
+	@Transactional(readOnly = true)
+	public PageResponse<CommentResponseDto> getCommentListByDiary(Long diaryId, Long cursorCommentId, int size) {
+		checkDiaryExists(diaryId);
+		Pageable pageable = PageRequest.of(0, size);
+		Slice<Comment> slice = commentRepository.findByDiaryIdWithCursor(diaryId, cursorCommentId, pageable);
+
+		List<CommentResponseDto> dtoList = slice.getContent().stream()
+			.map(CommentResponseDto::of)
+			.toList();
+
+		Long nextCursor = slice.hasNext() ? dtoList.getLast().commentId() : null;
+		return PageResponse.of(new SliceImpl<>(dtoList, pageable, slice.hasNext()), nextCursor);
+	}
 }