[feat] 댓글 다건 조회 기능 구현

src/main/java/com/back/domain/post/comment/controller/CommentController.java

@@ -7,11 +7,14 @@
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.tags.Tag;
 import jakarta.validation.Valid;
+import java.util.List;
 import lombok.RequiredArgsConstructor;
+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;
 
 @RestController
@@ -37,4 +40,12 @@ public RsData<CommentResponseDto> createComment(
     return RsData.successOf(commentService.createComment(postId, reqBody)); // code=200, message="success"
   }
 
+  @GetMapping
+  @Operation(summary = "댓글 다건 조회")
+  public RsData<List<CommentResponseDto>> getComments(
+      @PathVariable Long postId,
+      @RequestParam(required = false) Long lastId
+  ) {
+    return RsData.successOf(commentService.getComments(postId, lastId)); // code=200, message="success"
+  }
 }

src/main/java/com/back/domain/post/comment/repository/CommentRepository.java

@@ -1,10 +1,14 @@
 package com.back.domain.post.comment.repository;
 
 import com.back.domain.post.comment.entity.Comment;
+import java.util.List;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.stereotype.Repository;
 
 @Repository
 public interface CommentRepository extends JpaRepository<Comment, Long> {
 
+  List<Comment> findTop10ByPostIdOrderByIdDesc(Long postId);
+
+  List<Comment> findTop10ByPostIdAndIdLessThanOrderByIdDesc(Long postId, Long lastId);
 }

src/main/java/com/back/domain/post/comment/service/CommentService.java

@@ -8,6 +8,7 @@
 import com.back.domain.post.post.repository.PostRepository;
 import com.back.domain.user.entity.User;
 import com.back.global.rq.Rq;
+import java.util.List;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -36,4 +37,20 @@ public CommentResponseDto createComment(Long postId, CommentCreateRequestDto req
 
     return new CommentResponseDto(commentRepository.save(comment));
   }
+
+  // 댓글 다건 조회 로직 (무한스크롤)
+  @Transactional(readOnly = true)
+  public List<CommentResponseDto> getComments(Long postId, Long lastId) {
+    if (lastId == null) {
+      return commentRepository.findTop10ByPostIdOrderByIdDesc(postId)
+          .stream()
+          .map(CommentResponseDto::new)
+          .toList();
+    } else {
+      return commentRepository.findTop10ByPostIdAndIdLessThanOrderByIdDesc(postId, lastId)
+          .stream()
+          .map(CommentResponseDto::new)
+          .toList();
+    }
+  }
 }