Feat: 댓글 조회 API 구현 (#162)

src/main/java/com/back/domain/board/controller/CommentController.java

@@ -1,12 +1,17 @@
 package com.back.domain.board.controller;
 
+import com.back.domain.board.dto.CommentListResponse;
 import com.back.domain.board.dto.CommentRequest;
 import com.back.domain.board.dto.CommentResponse;
+import com.back.domain.board.dto.PageResponse;
 import com.back.domain.board.service.CommentService;
 import com.back.global.common.dto.RsData;
 import com.back.global.security.user.CustomUserDetails;
 import jakarta.validation.Valid;
 import lombok.RequiredArgsConstructor;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Sort;
+import org.springframework.data.web.PageableDefault;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
@@ -34,6 +39,21 @@ public ResponseEntity<RsData<CommentResponse>> createComment(
                 ));
     }
 
+    // 댓글 다건 조회
+    @GetMapping
+    public ResponseEntity<RsData<PageResponse<CommentListResponse>>> getComments(
+            @PathVariable Long postId,
+            @PageableDefault(sort = "createdAt", direction = Sort.Direction.ASC) Pageable pageable
+    ) {
+        PageResponse<CommentListResponse> response = commentService.getComments(postId, pageable);
+        return ResponseEntity
+                .status(HttpStatus.OK)
+                .body(RsData.success(
+                        "댓글 목록이 조회되었습니다.",
+                        response
+                ));
+    }
+
     // 댓글 수정
     @PutMapping("/{commentId}")
     public ResponseEntity<RsData<CommentResponse>> updateComment(
@@ -62,8 +82,8 @@ public ResponseEntity<RsData<Void>> deleteComment(
         return ResponseEntity
                 .status(HttpStatus.OK)
                 .body(RsData.success(
-                   "댓글이 삭제되었습니다.",
-                   null
+                        "댓글이 삭제되었습니다.",
+                        null
                 ));
     }
 }

src/main/java/com/back/domain/board/controller/CommentControllerDocs.java

@@ -1,7 +1,9 @@
 package com.back.domain.board.controller;
 
+import com.back.domain.board.dto.CommentListResponse;
 import com.back.domain.board.dto.CommentRequest;
 import com.back.domain.board.dto.CommentResponse;
+import com.back.domain.board.dto.PageResponse;
 import com.back.global.common.dto.RsData;
 import com.back.global.security.user.CustomUserDetails;
 import io.swagger.v3.oas.annotations.Operation;
@@ -10,6 +12,7 @@
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
 import io.swagger.v3.oas.annotations.responses.ApiResponses;
 import io.swagger.v3.oas.annotations.tags.Tag;
+import org.springframework.data.domain.Pageable;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.web.bind.annotation.*;
@@ -142,6 +145,115 @@ ResponseEntity<RsData<CommentResponse>> createComment(
             @AuthenticationPrincipal CustomUserDetails user
     );
 
+    @Operation(
+            summary = "댓글 목록 조회",
+            description = "특정 게시글에 달린 댓글 목록을 조회합니다. " +
+                    "부모 댓글 기준으로 페이징되며, 각 댓글의 대댓글(children) 목록이 함께 포함됩니다."
+    )
+    @ApiResponses({
+            @ApiResponse(
+                    responseCode = "200",
+                    description = "댓글 목록 조회 성공",
+                    content = @Content(
+                            mediaType = "application/json",
+                            examples = @ExampleObject(value = """
+                                    {
+                                      "success": true,
+                                      "code": "SUCCESS_200",
+                                      "message": "댓글 목록이 조회되었습니다.",
+                                      "data": {
+                                        "content": [
+                                          {
+                                            "commentId": 1,
+                                            "postId": 101,
+                                            "parentId": null,
+                                            "author": {
+                                              "id": 5,
+                                              "nickname": "홍길동"
+                                            },
+                                            "content": "부모 댓글",
+                                            "likeCount": 2,
+                                            "createdAt": "2025-09-22T11:30:00",
+                                            "updatedAt": "2025-09-22T11:30:00",
+                                            "children": [
+                                              {
+                                                "commentId": 2,
+                                                "postId": 101,
+                                                "parentId": 1,
+                                                "author": {
+                                                  "id": 5,
+                                                  "nickname": "홍길동"
+                                                },
+                                                "content": "자식 댓글",
+                                                "likeCount": 0,
+                                                "createdAt": "2025-09-22T11:35:00",
+                                                "updatedAt": "2025-09-22T11:35:00",
+                                                "children": []
+                                              }
+                                            ]
+                                          }
+                                        ],
+                                        "pageNumber": 0,
+                                        "pageSize": 10,
+                                        "totalElements": 1,
+                                        "totalPages": 1,
+                                        "last": true
+                                      }
+                                    }
+                                    """)
+                    )
+            ),
+            @ApiResponse(
+                    responseCode = "400",
+                    description = "잘못된 요청 (파라미터 오류)",
+                    content = @Content(
+                            mediaType = "application/json",
+                            examples = @ExampleObject(value = """
+                                    {
+                                      "success": false,
+                                      "code": "COMMON_400",
+                                      "message": "잘못된 요청입니다.",
+                                      "data": null
+                                    }
+                                    """)
+                    )
+            ),
+            @ApiResponse(
+                    responseCode = "404",
+                    description = "존재하지 않는 게시글",
+                    content = @Content(
+                            mediaType = "application/json",
+                            examples = @ExampleObject(value = """
+                                    {
+                                      "success": false,
+                                      "code": "POST_001",
+                                      "message": "존재하지 않는 게시글입니다.",
+                                      "data": null
+                                    }
+                                    """)
+                    )
+            ),
+            @ApiResponse(
+                    responseCode = "500",
+                    description = "서버 내부 오류",
+                    content = @Content(
+                            mediaType = "application/json",
+                            examples = @ExampleObject(value = """
+                                    {
+                                      "success": false,
+                                      "code": "COMMON_500",
+                                      "message": "서버 오류가 발생했습니다.",
+                                      "data": null
+                                    }
+                                    """)
+                    )
+            )
+    })
+    ResponseEntity<RsData<PageResponse<CommentListResponse>>> getComments(
+            @PathVariable Long postId,
+            Pageable pageable
+    );
+
     @Operation(
             summary = "댓글 수정",
             description = "로그인한 사용자가 자신이 작성한 댓글을 수정합니다."

src/main/java/com/back/domain/board/dto/AuthorResponse.java

@@ -1,6 +1,7 @@
 package com.back.domain.board.dto;
 
 import com.back.domain.user.entity.User;
+import com.querydsl.core.annotations.QueryProjection;
 
 /**
  * 작성자 응답 DTO
@@ -12,6 +13,9 @@ public record AuthorResponse(
         Long id,
         String nickname
 ) {
+    @QueryProjection
+    public AuthorResponse {}
+
     public static AuthorResponse from(User user) {
         return new AuthorResponse(
                 user.getId(),

src/main/java/com/back/domain/board/dto/CommentListResponse.java

@@ -0,0 +1,50 @@
+package com.back.domain.board.dto;
+
+import com.querydsl.core.annotations.QueryProjection;
+import lombok.Getter;
+import lombok.Setter;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+/**
+ * 댓글 목록 응답 DTO
+ */
+@Getter
+public class CommentListResponse {
+    private final Long commentId;
+    private final Long postId;
+    private final Long parentId;
+    private final AuthorResponse author;
+    private final String content;
+
+    @Setter
+    private long likeCount;
+
+    private final LocalDateTime createdAt;
+    private final LocalDateTime updatedAt;
+
+    @Setter
+    private List<CommentListResponse> children;
+
+    @QueryProjection
+    public CommentListResponse(Long commentId,
+                               Long postId,
+                               Long parentId,
+                               AuthorResponse author,
+                               String content,
+                               long likeCount,
+                               LocalDateTime createdAt,
+                               LocalDateTime updatedAt,
+                               List<CommentListResponse> children) {
+        this.commentId = commentId;
+        this.postId = postId;
+        this.parentId = parentId;
+        this.author = author;
+        this.content = content;
+        this.likeCount = likeCount;
+        this.createdAt = createdAt;
+        this.updatedAt = updatedAt;
+        this.children = children;
+    }
+}

src/main/java/com/back/domain/board/entity/Comment.java

@@ -41,6 +41,13 @@ public Comment(Post post, User user, String content) {
         this.user = user;
         this.content = content;
     }
+
+    public Comment(Post post, User user, String content, Comment parent) {
+        this.post = post;
+        this.user = user;
+        this.content = content;
+        this.parent = parent;
+    }
 
     // -------------------- 비즈니스 메서드 --------------------
     // 댓글 업데이트

src/main/java/com/back/domain/board/repository/CommentRepository.java

@@ -5,5 +5,5 @@
 import org.springframework.stereotype.Repository;
 
 @Repository
-public interface CommentRepository extends JpaRepository<Comment, Long> {
+public interface CommentRepository extends JpaRepository<Comment, Long>, CommentRepositoryCustom {
 }

src/main/java/com/back/domain/board/repository/CommentRepositoryCustom.java

@@ -0,0 +1,9 @@
+package com.back.domain.board.repository;
+
+import com.back.domain.board.dto.CommentListResponse;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
+
+public interface CommentRepositoryCustom {
+    Page<CommentListResponse> getCommentsByPostId(Long postId, Pageable pageable);
+}