[Feat]: 투표 게시글 조회 시 내가 선택했던 투표 번호가 응답으로 가도록 추가

Author: shihan00321

back/src/main/java/com/back/domain/poll/converter/PollConverter.java

@@ -77,4 +77,13 @@ public PollOptionResponse fromPollOptionJson(String voteContent) {
             throw new ApiException(ErrorCode.POLL_VOTE_INVALID_FORMAT);
         }
     }
+
+    public PollOptionResponse.VoteOption fromPollOptionInVoteOptionJson(String voteContent) {
+        if (voteContent == null) return null;
+        try {
+            return objectMapper.readValue(voteContent, PollOptionResponse.VoteOption.class);
+        } catch (JsonProcessingException e) {
+            throw new ApiException(ErrorCode.POLL_VOTE_INVALID_FORMAT);
+        }
+    }
 }

back/src/main/java/com/back/domain/poll/dto/PollOptionResponse.java

@@ -6,6 +6,7 @@
  * 투표 선택지 응답 DTO
  */
 public record PollOptionResponse(
+        List<Integer> selected,
         List<VoteOption> options
 ) {
     public record VoteOption(

back/src/main/java/com/back/domain/poll/repository/PollVoteRepository.java

@@ -10,11 +10,14 @@
 
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 /**
  * 투표 참여 엔티티에 대한 데이터베이스 접근을 담당하는 JpaRepository.
  */
 @Repository
 public interface PollVoteRepository extends JpaRepository<PollVote, Long> {
     List<PollVote> findByPostId(@Param("postId") Long postId);
+
+    Optional<PollVote> findByPostIdAndUserId(Long userId, Long postId);
 }

back/src/main/java/com/back/domain/post/service/PostService.java

@@ -3,6 +3,7 @@
 import com.back.domain.like.repository.PostLikeRepository;
 import com.back.domain.poll.converter.PollConverter;
 import com.back.domain.poll.dto.PollOptionResponse;
+import com.back.domain.poll.repository.PollVoteRepository;
 import com.back.domain.post.dto.PostDetailResponse;
 import com.back.domain.post.dto.PostRequest;
 import com.back.domain.post.dto.PostSearchCondition;
@@ -21,6 +22,8 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.Collections;
+import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -35,6 +38,7 @@ public class PostService {
     private final UserRepository userRepository;
     private final PostRepository postRepository;
     private final PostLikeRepository postLikeRepository;
+    private final PollVoteRepository pollVoteRepository;
     private final PostMappers postMappers;
     private final PollConverter pollConverter;
 
@@ -58,7 +62,15 @@ public PostDetailResponse getPost(Long userId, Long postId) {
             return postMappers.toDetailResponse(post, isLiked);
         }
 
-        PollOptionResponse pollResponse = pollConverter.fromPollOptionJson(post.getVoteContent());
+        List<PollOptionResponse.VoteOption> options =
+                pollConverter.fromPollOptionJson(post.getVoteContent()).options();
+
+        List<Integer> selected = pollVoteRepository.findByPostIdAndUserId(postId, userId)
+                .map(vote -> pollConverter.fromChoiceJson(vote.getChoiceJson()))
+                .orElse(Collections.emptyList());
+
+        PollOptionResponse pollResponse = new PollOptionResponse(selected, options);
+
         return postMappers.toDetailWithPollsResponse(post, isLiked, pollResponse);
     }