[Feat]: 댓글 좋아요 추가, 삭제 기능 추가

# Conflicts:
#	back/src/main/java/com/back/domain/comment/repository/CommentRepository.java

Author: shihan00321

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

@@ -58,4 +58,14 @@ public void checkUser(Long userId) {
     public void updateContent(String content) {
         this.content = content;
     }
+
+    public void incrementLikeCount() {
+        this.likeCount++;
+    }
+
+    public void decrementLikeCount() {
+        if (this.likeCount > 0) {
+            this.likeCount--;
+        }
+    }
 }

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

@@ -1,13 +1,17 @@
 package com.back.domain.comment.repository;
 
 import com.back.domain.comment.entity.Comment;
+import jakarta.persistence.LockModeType;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Lock;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
+import java.util.Optional;
+
 /**
  * 댓글 엔티티에 대한 데이터베이스 접근을 담당하는 JpaRepository.
  */
@@ -17,4 +21,8 @@ public interface CommentRepository extends JpaRepository<Comment, Long> {
     Page<Comment> findCommentsByPostId(@Param("postId") Long postId, Pageable pageable);
 
     int countByUserId(Long userId);
+
+    @Lock(LockModeType.PESSIMISTIC_WRITE)
+    @Query("SELECT c FROM Comment c WHERE c.id = :commentId")
+    Optional<Comment> findByIdWithLock(@Param("commentId") Long commentId);
 }

back/src/main/java/com/back/domain/like/controller/LikeController.java

@@ -28,4 +28,20 @@ public ResponseEntity<Void> removeLike(@PathVariable Long postId, @Authenticatio
         likeService.removeLike(postId, cs.getUser().getId());
         return ResponseEntity.ok(null);
     }
+
+    @PostMapping("/{postId}/comments/{commentId}/likes")
+    public ResponseEntity<Void> addCommentLike(@PathVariable Long postId,
+                                               @PathVariable Long commentId,
+                                               @AuthenticationPrincipal CustomUserDetails cs) {
+        likeService.addCommentLike(cs.getUser().getId(), postId, commentId);
+        return ResponseEntity.status(HttpStatus.CREATED).body(null);
+    }
+
+    @DeleteMapping("/{postId}/comments/{commentId}/likes")
+    public ResponseEntity<Void> removeCommentLike(@PathVariable Long postId,
+                                                  @PathVariable Long commentId,
+                                                  @AuthenticationPrincipal CustomUserDetails cs) {
+        likeService.removeCommentLike(cs.getUser().getId(), postId, commentId);
+        return ResponseEntity.ok(null);
+    }
 }

back/src/main/java/com/back/domain/like/repository/CommentLikeRepository.java

@@ -2,6 +2,7 @@
 
 import com.back.domain.like.entity.CommentLike;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Modifying;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
@@ -15,4 +16,10 @@
 public interface CommentLikeRepository extends JpaRepository<CommentLike, Long> {
     @Query("SELECT cl.comment.id FROM CommentLike cl WHERE cl.user.id = :userId AND cl.comment.id IN :commentIds")
     Set<Long> findLikedCommentsIdsByUserAndCommentIds(@Param("userId") Long userId, @Param("commentIds") Set<Long> commentIds);
+
+    boolean existsByCommentIdAndUserId(Long commentId, Long userId);
+
+    @Modifying
+    @Query("DELETE FROM CommentLike cl WHERE cl.comment.id = :commentId AND cl.user.id = :userId")
+    int deleteByCommentIdAndUserId(@Param("commentId") Long commentId, @Param("userId") Long userId);
 }

back/src/main/java/com/back/domain/like/service/LikeService.java

@@ -1,5 +1,8 @@
 package com.back.domain.like.service;
 
+import com.back.domain.comment.entity.Comment;
+import com.back.domain.comment.repository.CommentRepository;
+import com.back.domain.like.entity.CommentLike;
 import com.back.domain.like.entity.PostLike;
 import com.back.domain.like.repository.CommentLikeRepository;
 import com.back.domain.like.repository.PostLikeRepository;
@@ -23,6 +26,7 @@ public class LikeService {
 
     private final PostLikeRepository postLikeRepository;
     private final CommentLikeRepository commentLikeRepository;
+    private final CommentRepository commentRepository;
     private final PostRepository postRepository;
     private final UserRepository userRepository;
 
@@ -55,11 +59,48 @@ public void removeLike(Long postId, Long userId) {
         post.decrementLikeCount();
     }
 
+    @Transactional
+    public void addCommentLike(Long userId, Long postId, Long commentId) {
+        Comment comment = commentRepository.findByIdWithLock(commentId)
+                .orElseThrow(() -> new ApiException(ErrorCode.COMMENT_NOT_FOUND));
+
+        if (commentLikeRepository.existsByCommentIdAndUserId(postId, userId)) {
+            throw new ApiException(ErrorCode.COMMENT_ALREADY_LIKED);
+        }
+
+        CommentLike commentLike = createCommentLike(comment, userId);
+
+        commentLikeRepository.save(commentLike);
+        comment.incrementLikeCount();
+    }
+
+    @Transactional
+    public void removeCommentLike(Long userId, Long postId, Long commentId) {
+        Comment comment = commentRepository.findByIdWithLock(commentId)
+                .orElseThrow(() -> new ApiException(ErrorCode.COMMENT_NOT_FOUND));
+
+        boolean deleted = commentLikeRepository.deleteByCommentIdAndUserId(commentId, userId) > 0;
+
+        if (!deleted) {
+            throw new ApiException(ErrorCode.LIKE_NOT_FOUND);
+        }
+
+        comment.decrementLikeCount();
+    }
+
     private PostLike createPostLike(Post post, Long userId) {
         User userReference = userRepository.getReferenceById(userId);
         return PostLike.builder()
                 .post(post)
                 .user(userReference)
                 .build();
     }
+
+    private CommentLike createCommentLike(Comment comment, Long userId) {
+        User userReference = userRepository.getReferenceById(userId);
+        return CommentLike.builder()
+                .comment(comment)
+                .user(userReference)
+                .build();
+    }
 }

back/src/main/java/com/back/global/exception/ErrorCode.java

@@ -34,6 +34,7 @@ public enum ErrorCode {
 
     // Comment Errors
     COMMENT_NOT_FOUND(HttpStatus.NOT_FOUND, "CM001", "Comment Not Found"),
+    COMMENT_ALREADY_LIKED(HttpStatus.BAD_REQUEST, "CM002", "Comment Already Liked"),
 
     // Session Errors
     SESSION_NOT_FOUND(HttpStatus.NOT_FOUND, "S001", "Session Not Found"),