refactor: 댓글 정책 변경에 따른 리팩터링

src/main/java/com/example/solidconnection/community/comment/domain/Comment.java

@@ -40,6 +40,9 @@ public class Comment extends BaseEntity {
     @Column(length = 255)
     private String content;
 
+    @Column(name = "is_deleted", columnDefinition = "boolean default false", nullable = false)
+    private boolean isDeleted = false;
+
     @ManyToOne(fetch = FetchType.LAZY)
     @JoinColumn(name = "post_id")
     private Post post;
@@ -102,6 +105,6 @@ public void updateContent(String content) {
     }
 
     public void deprecateComment() {
-        this.content = null;
+        this.isDeleted = true;
     }
 }

src/main/java/com/example/solidconnection/community/comment/dto/PostFindCommentResponse.java

@@ -20,11 +20,11 @@ public static PostFindCommentResponse from(Boolean isOwner, Comment comment, Sit
         return new PostFindCommentResponse(
                 comment.getId(),
                 getParentCommentId(comment),
-                comment.getContent(),
+                getDisplayContent(comment),
                 isOwner,
                 comment.getCreatedAt(),
                 comment.getUpdatedAt(),
-                PostFindSiteUserResponse.from(siteUser)
+                getDisplaySiteUserResponse(comment, siteUser)
         );
     }
 
@@ -34,4 +34,13 @@ private static Long getParentCommentId(Comment comment) {
         }
         return null;
     }
+
+    private static String getDisplayContent(Comment comment)
+    {
+        return comment.isDeleted() ? "" : comment.getContent();
+    }
+
+    private static PostFindSiteUserResponse getDisplaySiteUserResponse(Comment comment, SiteUser siteUser) {
+        return comment.isDeleted() ? null : PostFindSiteUserResponse.from(siteUser);
+    }
 }

src/main/java/com/example/solidconnection/community/comment/repository/CommentRepository.java

@@ -16,14 +16,14 @@ public interface CommentRepository extends JpaRepository<Comment, Long> {
             WITH RECURSIVE CommentTree AS (
                     SELECT
                             id, parent_id, post_id, site_user_id, content,
-                            created_at, updated_at,
+                            created_at, updated_at, is_deleted,
                             0 AS level, CAST(id AS CHAR(255)) AS path
                     FROM comment
                     WHERE post_id = :postId AND parent_id IS NULL
                     UNION ALL
                     SELECT
                             c.id, c.parent_id, c.post_id, c.site_user_id, c.content,
-                            c.created_at, c.updated_at,
+                            c.created_at, c.updated_at, c.is_deleted,
                             ct.level + 1, CONCAT(ct.path, '->', c.id)
                     FROM comment c
                     INNER JOIN CommentTree ct ON c.parent_id = ct.id

src/main/java/com/example/solidconnection/community/comment/service/CommentService.java

@@ -17,8 +17,11 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 import static com.example.solidconnection.common.exception.ErrorCode.CAN_NOT_UPDATE_DEPRECATED_COMMENT;
@@ -36,14 +39,47 @@ public class CommentService {
 
     @Transactional(readOnly = true)
     public List<PostFindCommentResponse> findCommentsByPostId(SiteUser siteUser, Long postId) {
-        SiteUser commentOwner = siteUserRepository.findById(siteUser.getId())
-                .orElseThrow(() -> new CustomException(USER_NOT_FOUND));
-        return commentRepository.findCommentTreeByPostId(postId)
+        List<Comment> allComments = commentRepository.findCommentTreeByPostId(postId);
+        List<Comment> filteredComments = filterCommentsByDeletionRules(allComments);
+
+        Set<Long> userIds = filteredComments.stream()
+                .map(Comment::getSiteUserId)
+                .collect(Collectors.toSet());
+
+        Map<Long, SiteUser> userMap = siteUserRepository.findAllById(userIds)
                 .stream()
-                .map(comment -> PostFindCommentResponse.from(isOwner(comment, siteUser), comment, siteUser))
+                .collect(Collectors.toMap(SiteUser::getId, user -> user));
+
+        return filteredComments.stream()
+                .map(comment -> PostFindCommentResponse.from(
+                        isOwner(comment, siteUser), comment, userMap.get(comment.getSiteUserId())))
                 .collect(Collectors.toList());
     }
 
+    private List<Comment> filterCommentsByDeletionRules(List<Comment> comments) {
+        Map<Long, List<Comment>> commentsByParent = comments.stream()
+                .filter(comment -> comment.getParentComment() != null)
+                .collect(Collectors.groupingBy(comment -> comment.getParentComment().getId()));
+
+        List<Comment> result = new ArrayList<>();
+
+        List<Comment> parentComments = comments.stream()
+                .filter(comment -> comment.getParentComment() == null)
+                .toList();
+        for (Comment parent : parentComments) {
+            List<Comment> children = commentsByParent.getOrDefault(parent.getId(), List.of());
+            boolean allDeleted = parent.isDeleted() &&
+                    children.stream().allMatch(Comment::isDeleted);
+            if (!allDeleted) {
+                result.add(parent);
+                result.addAll(children.stream()
+                        .filter(child -> !child.isDeleted())
+                        .toList());
+            }
+        }
+        return result;
+    }
+
     private Boolean isOwner(Comment comment, SiteUser siteUser) {
         return Objects.equals(comment.getSiteUserId(), siteUser.getId());
     }
@@ -99,7 +135,7 @@ public CommentDeleteResponse deleteCommentById(SiteUser siteUser, Long commentId
             comment.resetPostAndParentComment();
             commentRepository.deleteById(commentId);
             // 대댓글 삭제 이후, 부모댓글이 무의미하다면 이역시 삭제합니다.
-            if (parentComment.getCommentList().isEmpty() && parentComment.getContent() == null) {
+            if (parentComment.getCommentList().isEmpty() && parentComment.isDeleted()) {
                 parentComment.resetPostAndParentComment();
                 commentRepository.deleteById(parentComment.getId());
             }

src/main/resources/db/migration/V22_add_is_deleted_to_comment.sql

@@ -0,0 +1,2 @@
+ALTER TABLE comment
+    ADD COLUMN is_deleted BOOLEAN NOT NULL DEFAULT FALSE;

src/test/java/com/example/solidconnection/community/comment/service/CommentServiceTest.java

@@ -15,6 +15,7 @@
 import com.example.solidconnection.community.post.domain.PostCategory;
 import com.example.solidconnection.community.post.fixture.PostFixture;
 import com.example.solidconnection.siteuser.domain.SiteUser;
+import com.example.solidconnection.siteuser.dto.PostFindSiteUserResponse;
 import com.example.solidconnection.siteuser.fixture.SiteUserFixture;
 import com.example.solidconnection.support.TestContainerSpringBootTest;
 import jakarta.transaction.Transactional;
@@ -108,6 +109,85 @@ class 댓글_조회_테스트 {
                             ))
             );
         }
+
+        @Test
+        void 부모댓글과_대댓글이_모두_삭제되면_응답에서_제외한다() {
+            // given
+            Comment parentComment = commentFixture.부모_댓글("부모 댓글", post, user1);
+            Comment childComment1 = commentFixture.자식_댓글("자식 댓글1", post, user2, parentComment);
+            Comment childComment2 = commentFixture.자식_댓글("자식 댓글2", post, user2, parentComment);
+
+            parentComment.deprecateComment();
+            childComment1.deprecateComment();
+            childComment2.deprecateComment();
+            commentRepository.saveAll(List.of(parentComment, childComment1, childComment2));
+
+            // when
+            List<PostFindCommentResponse> responses = commentService.findCommentsByPostId(user1, post.getId());
+
+            // then
+            assertAll(
+                    () -> assertThat(responses).isEmpty()
+            );
+        }
+
+        @Test
+        void 부모댓글이_삭제된_경우에도_자식댓글이_존재하면_자식댓글의_내용만_반환한다() {
+            // given
+            Comment parentComment = commentFixture.부모_댓글("부모 댓글", post, user1);
+            Comment childComment1 = commentFixture.자식_댓글("자식 댓글1", post, user2, parentComment);
+            Comment childComment2 = commentFixture.자식_댓글("자식 댓글2", post, user2, parentComment);
+
+            parentComment.deprecateComment();
+            commentRepository.saveAll(List.of(parentComment, childComment1, childComment2));
+
+            // when
+            List<PostFindCommentResponse> responses = commentService.findCommentsByPostId(user1, post.getId());
+
+            // then
+            assertAll(
+                    () -> assertThat(responses).hasSize(3),
+                    () -> assertThat(responses)
+                            .extracting(PostFindCommentResponse::id)
+                            .containsExactlyInAnyOrder(parentComment.getId(), childComment1.getId(), childComment2.getId()),
+                    () -> assertThat(responses)
+                            .filteredOn(response -> response.id().equals(parentComment.getId()))
+                            .extracting(PostFindCommentResponse::content)
+                            .containsExactly(""),
+                    () -> assertThat(responses)
+                            .filteredOn(response -> !response.id().equals(parentComment.getId()))
+                            .extracting(PostFindCommentResponse::content)
+                            .containsExactlyInAnyOrder("자식 댓글1", "자식 댓글2")
+            );
+        }
+
+        @Test
+        void 부모댓글이_삭제된_경우_부모댓글의_사용자정보는_null이고_자식댓글의_사용자정보는_정상적으로_반환한다() {
+            // given
+            Comment parentComment = commentFixture.부모_댓글("부모 댓글", post, user1);
+            Comment childComment1 = commentFixture.자식_댓글("자식 댓글1", post, user2, parentComment);
+            Comment childComment2 = commentFixture.자식_댓글("자식 댓글2", post, user2, parentComment);
+
+            parentComment.deprecateComment();
+            commentRepository.saveAll(List.of(parentComment, childComment1, childComment2));
+
+            // when
+            List<PostFindCommentResponse> responses = commentService.findCommentsByPostId(user1, post.getId());
+
+            // then
+            assertAll(
+                    () -> assertThat(responses)
+                            .filteredOn(response -> response.id().equals(parentComment.getId()))
+                            .extracting(PostFindCommentResponse::postFindSiteUserResponse)
+                            .containsExactly((PostFindSiteUserResponse) null),
+                    () -> assertThat(responses)
+                            .filteredOn(response -> !response.id().equals(parentComment.getId()))
+                            .extracting(PostFindCommentResponse::postFindSiteUserResponse)
+                            .isNotNull()
+                            .extracting(PostFindSiteUserResponse::id)
+                            .containsExactlyInAnyOrder(user2.getId(), user2.getId())
+            );
+        }
     }
 
     @Nested
@@ -281,7 +361,8 @@ class 댓글_삭제_테스트 {
             // then
             Comment deletedComment = commentRepository.findById(response.id()).orElseThrow();
             assertAll(
-                    () -> assertThat(deletedComment.getContent()).isNull(),
+                    () -> assertThat(deletedComment.getContent()).isEqualTo("부모 댓글"),
+                    () -> assertThat(deletedComment.isDeleted()).isTrue(),
                     () -> assertThat(deletedComment.getCommentList())
                             .extracting(Comment::getId)
                             .containsExactlyInAnyOrder(childComment.getId()),
@@ -316,27 +397,6 @@ class 댓글_삭제_테스트 {
             );
         }
 
-        @Test
-        @Transactional
-        void 대댓글을_삭제하고_부모댓글이_삭제된_상태면_부모댓글도_삭제된다() {
-            // given
-            Comment parentComment = commentFixture.부모_댓글("부모 댓글", post, user1);
-            Comment childComment = commentFixture.자식_댓글("자식 댓글", post, user2, parentComment);
-            List<Comment> comments = post.getCommentList();
-            int expectedCommentsCount = comments.size() - 2;
-            parentComment.deprecateComment();
-
-            // when
-            CommentDeleteResponse response = commentService.deleteCommentById(user2, childComment.getId());
-
-            // then
-            assertAll(
-                    () -> assertThat(commentRepository.findById(response.id())).isEmpty(),
-                    () -> assertThat(commentRepository.findById(parentComment.getId())).isEmpty(),
-                    () -> assertThat(post.getCommentList()).hasSize(expectedCommentsCount)
-            );
-        }
-
         @Test
         void 다른_사용자의_댓글을_삭제하면_예외_응답을_반환한다() {
             // given