SSE 30초 주기 알림 구현

src/main/java/com/smart/watchboard/WatchboardApplication.java

@@ -2,7 +2,10 @@
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.scheduling.annotation.EnableScheduling;
+
 @SpringBootApplication
+@EnableScheduling
 public class WatchboardApplication {
 
 	public static void main(String[] args) {

src/main/java/com/smart/watchboard/common/support/ScheduledTask.java

@@ -0,0 +1,17 @@
+package com.smart.watchboard.common.support;
+
+import com.smart.watchboard.service.SseService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+@Component
+@RequiredArgsConstructor
+public class ScheduledTask {
+    private final SseService sseService;
+
+    @Scheduled(fixedRate = 30000)
+    public void executeNotifyTask() {
+        sseService.notifyCycle();
+    }
+}

src/main/java/com/smart/watchboard/repository/EmitterRepository.java

@@ -4,8 +4,10 @@
 import org.springframework.stereotype.Repository;
 import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
 
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
 
 @Repository
 @RequiredArgsConstructor
@@ -23,4 +25,9 @@ public void deleteById(Long id) {
     public SseEmitter get(Long id) {
         return emitters.get(id);
     }
+
+    public List<Long> getAllKeys() {
+        return emitters.keySet().stream()
+                .collect(Collectors.toList());
+    }
 }

src/main/java/com/smart/watchboard/service/SseService.java

@@ -51,6 +51,24 @@ public void notify(Long documentId, List<String> keywords) {
         sendToClient(documentId, keywords);
     }
 
+    public void notifyCycle() {
+        sendCycle();
+    }
+
+    private void sendCycle() {
+        List<Long> keys = emitterRepository.getAllKeys();
+        for (Long documentId : keys) {
+            SseEmitter emitter = emitterRepository.get(documentId);
+            try {
+                emitter.send(SseEmitter.event().id(String.valueOf(documentId)).name("ping").data("ping"));
+            } catch (IOException exception) {
+                emitterRepository.deleteById(documentId);
+                emitter.completeWithError(exception);
+            }
+
+        }
+    }
+
     private void sendToClientFirst(Long documentId, Object data) {
         SseEmitter emitter = emitterRepository.get(documentId);
         if (emitter != null) {