refactor : 채팅 메시지 전송 리팩토링

src/main/java/org/swyp/linkit/domain/notification/dto/NotificationDto.java

@@ -21,8 +21,9 @@ public class NotificationDto {
     private Long refId;
     private boolean isRead;
     private LocalDateTime createdAt;
+    private String message;
 
-    public static NotificationDto from(Notification notification) {
+    public static NotificationDto from(Notification notification, String message) {
         return NotificationDto.builder()
                 .id(notification.getId())
                 .receiverId(notification.getReceiver().getId())
@@ -31,6 +32,7 @@ public static NotificationDto from(Notification notification) {
                 .refId(notification.getRefId())
                 .isRead(notification.isRead())
                 .createdAt(notification.getCreatedAt())
+                .message(message)
                 .build();
     }
 }

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

@@ -24,8 +24,11 @@
 
 import java.time.LocalDateTime;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 @Slf4j
@@ -71,7 +74,7 @@ public NotificationDto createNotification(Long receiverId, Long senderId, Notifi
         publishNotificationToRedis(savedNotification, senderNickname, message);
 
         log.info("알림 생성 및 발송: receiverId={}, type={}, refId={}", receiverId, type, refId);
-        return NotificationDto.from(savedNotification);
+        return NotificationDto.from(savedNotification, message);
     }
 
     @Override
@@ -87,7 +90,7 @@ public NotificationDto createSystemNotification(Long receiverId, NotificationTyp
         publishNotificationToRedis(savedNotification, "시스템", message);
 
         log.info("시스템 알림 생성 및 발송: receiverId={}, type={}, refId={}", receiverId, type, refId);
-        return NotificationDto.from(savedNotification);
+        return NotificationDto.from(savedNotification, message);
     }
 
     // ===== 미읽음 개수 조회 =====
@@ -143,8 +146,23 @@ public NotificationListResponseDto getNotifications(Long userId) {
         combinedNotifications.addAll(unreadNotifications);
         combinedNotifications.addAll(readNotifications);
 
+        // sender nickname 배치 조회
+        Set<Long> senderIds = combinedNotifications.stream()
+                .map(Notification::getSenderId)
+                .filter(Objects::nonNull)
+                .collect(Collectors.toSet());
+        Map<Long, String> nicknameMap = senderIds.isEmpty()
+                ? Collections.emptyMap()
+                : userRepository.findAllById(senderIds).stream()
+                        .collect(Collectors.toMap(User::getId,
+                                u -> u.getNickname() != null ? u.getNickname() : "시스템"));
+
         List<NotificationDto> notificationDtos = combinedNotifications.stream()
-                .map(NotificationDto::from)
+                .map(n -> {
+                    String senderNickname = nicknameMap.getOrDefault(n.getSenderId(), "시스템");
+                    String message = generateNotificationMessage(n.getNotificationType(), senderNickname);
+                    return NotificationDto.from(n, message);
+                })
                 .collect(Collectors.toList());
 
         return NotificationListResponseDto.of(notificationDtos, unreadNotifications.size());