PR : SSE 에러 해결

src/main/java/com/juu/juulabel/api/service/notification/NotificationService.java

@@ -1,5 +1,6 @@
 package com.juu.juulabel.api.service.notification;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import com.juu.juulabel.api.dto.request.CreateNotificationRequest;
 import com.juu.juulabel.api.dto.request.NotificationListRequest;
 import com.juu.juulabel.api.dto.response.NotificationListResponse;
@@ -26,7 +27,11 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
+import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
 
 @Slf4j
 @Service
@@ -57,26 +62,45 @@ public SseEmitter subscribe(Member member, String lastEventId, HttpServletRespon
         // 첫 연결 시 503 Service Unavailable 방지용 더미 Event 전송
         sendToClient(emitter, emitterId, "알림 서버 연결 성공. [memberId=" + memberId + "]");
 
+        // Ping 전송 설정
+        sendPing(emitter, emitterId);
+
         if (!lastEventId.isEmpty()) {
             sendLostData(lastEventId, memberId, emitter);
         }
 
         return emitter;
     }
 
+    private void sendPing(SseEmitter emitter, String emitterId) {
+        ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
+        scheduler.scheduleAtFixedRate(() -> {
+            try {
+                emitter.send(SseEmitter.event()
+                    .id(emitterId)
+                    .name("ping")
+                    .data("ping"));
+            } catch (IOException e) {
+                emitter.completeWithError(e);
+                scheduler.shutdown();
+            }
+        }, 0, 30, TimeUnit.SECONDS); // 30초 간격으로 ping 전송
+    }
+
+
     private void configureSse(HttpServletResponse response) {
-        response.setHeader("Content-Type", "text/event-stream");
         response.setHeader("Cache-Control", "no-cache");
         response.setHeader("Connection", "keep-alive");
         response.setHeader("Access-Control-Allow-Origin", "*");
     }
 
     private void sendToClient(SseEmitter emitter, String emitterId, Object data) {
         try {
+            String jsonData = new ObjectMapper().writeValueAsString(data); // JSON 변환
             emitter.send(SseEmitter.event()
                 .id(emitterId)
                 .name("sse")
-                .data(data)
+                .data(jsonData)
             );
         } catch (IOException exception) {
             emitterRepository.deleteById(emitterId);
@@ -94,7 +118,7 @@ private void sendLostData(String lastEventId, Long memberId, SseEmitter emitter)
     }
 
     private String makeTimeIncludeId(Long memberId) { // (3)
-        return memberId + "_" + System.currentTimeMillis();
+        return memberId + "_" + UUID.randomUUID();
     }
 
     @Transactional