fix : 알림 도메인 RedisConfig 리스너 추가 및 이미지 전송 NPE 이슈 수정

src/main/java/org/swyp/linkit/domain/chat/service/ChatRoomService.java

@@ -9,6 +9,7 @@
 import org.swyp.linkit.domain.chat.entity.ChatRoom;
 import org.swyp.linkit.domain.chat.entity.ChatRoomDelete;
 import org.swyp.linkit.domain.chat.entity.ChatRoomStatus;
+import org.swyp.linkit.domain.chat.entity.MessageType;
 import org.swyp.linkit.domain.chat.repository.ChatMessageRepository;
 import org.swyp.linkit.domain.chat.repository.ChatRoomDeleteRepository;
 import org.swyp.linkit.domain.chat.repository.ChatRoomRepository;
@@ -86,7 +87,7 @@ public List<ChatRoomDto> findRoomsByUserId(Long userId) {
                     ChatMessage lastMessage = (ChatMessage) row[1];
 
                     // 마지막 메시지 내용
-                    String lastMessageContent = lastMessage != null ? lastMessage.getContent() : null;
+                    String lastMessageContent = lastMessage != null ? resolveLastMessageContent(lastMessage) : null;
 
                     // 상대방 정보 (연관관계로 바로 접근)
                     boolean isMentor = room.getMentorId().equals(userId);
@@ -120,7 +121,7 @@ public ChatRoomDto findDtoById(Long roomId, Long currentUserId) {
         String lastMessageContent = null;
         if (room.getLastMessageId() != null) {
             lastMessageContent = chatMessageRepository.findById(room.getLastMessageId())
-                    .map(ChatMessage::getContent)
+                    .map(this::resolveLastMessageContent)
                     .orElse(null);
         }
 
@@ -180,6 +181,13 @@ public boolean isMentor(ChatRoom room, Long userId) {
 
     // === Private Helper Methods ===
 
+    private String resolveLastMessageContent(ChatMessage message) {
+        if (message.getMessageType() == MessageType.IMAGE) {
+            return "[이미지]";
+        }
+        return message.getContent();
+    }
+
     private User findUserById(Long userId) {
         return userRepository.findById(userId)
                 .orElseThrow(() -> new UserNotFoundException("User not found: " + userId));

src/main/java/org/swyp/linkit/domain/notification/service/NotificationServiceImpl.java

@@ -69,7 +69,7 @@ public NotificationDto createNotification(Long receiverId, Long senderId, Notifi
         Notification savedNotification = notificationRepository.save(notification);
 
         // WebSocket 실시간 알림 발송
-        String senderNickname = sender != null ? sender.getNickname() : "시스템";
+        String senderNickname = resolveNickname(sender);
         String message = generateNotificationMessage(type, senderNickname);
         publishNotificationToRedis(savedNotification, senderNickname, message);
 
@@ -154,8 +154,10 @@ public NotificationListResponseDto getNotifications(Long userId) {
         Map<Long, String> nicknameMap = senderIds.isEmpty()
                 ? Collections.emptyMap()
                 : userRepository.findAllById(senderIds).stream()
-                        .collect(Collectors.toMap(User::getId,
-                                u -> u.getNickname() != null ? u.getNickname() : "시스템"));
+                        .collect(Collectors.toMap(
+                                User::getId,
+                                u -> hasValidNickname(u) ? u.getNickname() : "알 수 없음",
+                                (existing, replacement) -> existing));
 
         List<NotificationDto> notificationDtos = combinedNotifications.stream()
                 .map(n -> {
@@ -240,6 +242,18 @@ public int markAllAsRead(Long userId) {
 
     // ===== Private Methods =====
 
+    /**
+     * sender가 null이면 "시스템", 존재하지만 닉네임이 없으면 "알 수 없음"
+     */
+    private String resolveNickname(User sender) {
+        if (sender == null) return "시스템";
+        return hasValidNickname(sender) ? sender.getNickname() : "알 수 없음";
+    }
+
+    private boolean hasValidNickname(User user) {
+        return user.getNickname() != null && !user.getNickname().isBlank();
+    }
+
     private User findUserById(Long userId) {
         return userRepository.findById(userId)
                 .orElseThrow(UserNotFoundException::new);

src/main/java/org/swyp/linkit/global/config/RedisConfig.java

@@ -8,12 +8,14 @@
 import org.springframework.data.redis.listener.PatternTopic;
 import org.springframework.data.redis.listener.RedisMessageListenerContainer;
 import org.swyp.linkit.domain.chat.redis.RedisChatSubscriber;
+import org.swyp.linkit.domain.notification.redis.RedisNotificationSubscriber;
 
 @Profile("!test")
 @Configuration
 public class RedisConfig {
 
     private static final String CHAT_CHANNEL_PATTERN = "chat:room:*";
+    private static final String NOTIFICATION_CHANNEL_PATTERN = "notification:user:*";
 
     @Bean
     public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory connectionFactory) {
@@ -23,11 +25,13 @@ public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory connection
     @Bean
     public RedisMessageListenerContainer redisMessageListenerContainer(
             RedisConnectionFactory connectionFactory,
-            RedisChatSubscriber redisChatSubscriber) {
+            RedisChatSubscriber redisChatSubscriber,
+            RedisNotificationSubscriber redisNotificationSubscriber) {
 
         RedisMessageListenerContainer container = new RedisMessageListenerContainer();
         container.setConnectionFactory(connectionFactory);
         container.addMessageListener(redisChatSubscriber, new PatternTopic(CHAT_CHANNEL_PATTERN));
+        container.addMessageListener(redisNotificationSubscriber, new PatternTopic(NOTIFICATION_CHANNEL_PATTERN));
         return container;
     }
 }