[feat] 게시글 추천, 댓글 작성 시 알림 이벤트 구현

src/main/java/com/back/domain/notification/controller/NotificationController.java

@@ -3,20 +3,27 @@
 import com.back.domain.notification.dto.NotificationGoResponseDto;
 import com.back.domain.notification.dto.NotificationListResponseDto;
 import com.back.domain.notification.dto.NotificationSettingDto;
-import com.back.domain.notification.service.NotificationSettingService;
 import com.back.domain.notification.dto.NotificationSettingUpdateRequestDto;
-import jakarta.validation.Valid;
 import com.back.domain.notification.service.NotificationService;
+import com.back.domain.notification.service.NotificationSettingService;
 import com.back.global.rsData.RsData;
+import jakarta.validation.Valid;
 import jakarta.validation.constraints.Max;
 import jakarta.validation.constraints.Min;
+import java.time.LocalDateTime;
 import lombok.RequiredArgsConstructor;
 import org.springframework.format.annotation.DateTimeFormat;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.validation.annotation.Validated;
-import org.springframework.web.bind.annotation.*;
-
-import java.time.LocalDateTime;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PatchMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
 
 @RestController
 @RequestMapping("/api/me")
@@ -27,6 +34,13 @@ public class NotificationController {
     private final NotificationService notificationService;
     private final NotificationSettingService notificationSettingService;
 
+    // SSE 연결
+    // produces = "text/event-stream": 응답 형식이 SSE임을 명시
+    @GetMapping(value = "/subscribe", produces = "text/event-stream")
+    public SseEmitter subscribe() {
+        return notificationService.subscribe();
+    }
+
     @GetMapping("/notifications")
     public RsData<NotificationListResponseDto> getNotifications(
             @AuthenticationPrincipal(expression = "id") Long userId,

src/main/java/com/back/domain/notification/entity/Notification.java

@@ -42,6 +42,10 @@ public class Notification {
     @Column(name = "created_at", nullable = false, updatable = false)
     private LocalDateTime createdAt;
 
+    // 알림 메시지
+    @Column(name = "message", nullable = false, columnDefinition = "TEXT")
+    private String message;
+
     public void markRead() {
         this.read = true;
     }

src/main/java/com/back/domain/notification/service/NotificationService.java

@@ -4,22 +4,46 @@
 import com.back.domain.notification.dto.NotificationItemDto;
 import com.back.domain.notification.dto.NotificationListResponseDto;
 import com.back.domain.notification.entity.Notification;
+import com.back.domain.notification.enums.NotificationType;
 import com.back.domain.notification.repository.NotificationRepository;
+import com.back.domain.post.post.entity.Post;
+import com.back.domain.user.entity.User;
 import com.back.global.exception.ServiceException;
+import com.back.global.rq.Rq;
+import java.time.LocalDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import lombok.RequiredArgsConstructor;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
-
-import java.time.LocalDateTime;
-import java.util.ArrayList;
-import java.util.List;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
 
 @Service
 @RequiredArgsConstructor
 public class NotificationService {
 
     private final NotificationRepository notificationRepository;
+    private final Rq rq;
+
+    // 연결을 관리하기 위한 Map (key: userId)
+  // ConcurrentHashMap: 멀티스레드 환경에서 컬렉션을 안전하게 사용 가능
+    private final Map<Long, SseEmitter> emitters = new ConcurrentHashMap<>();
+
+    // 구독 (클라이언트 연결 유지)
+    public SseEmitter subscribe() {
+      User user = rq.getActor(); // 현재 로그인한 사용자의 정보 가져오기
+      SseEmitter emitter = new SseEmitter(Long.MAX_VALUE);
+      emitters.put(user.getId(), emitter);
+
+      // 연결 종료 시 제거
+      emitter.onCompletion(() -> emitters.remove(user.getId()));
+      emitter.onTimeout(() -> emitters.remove(user.getId()));
+
+      return emitter;
+    }
 
     @Transactional(readOnly = true)
     public NotificationListResponseDto getNotifications(Long userId, LocalDateTime lastCreatedAt, Long lastId, int limit) {
@@ -63,4 +87,30 @@ public NotificationGoResponseDto markAsReadAndGetPostLink(Long userId, Long noti
         String apiUrl = "/api/posts/" + postId;
         return new NotificationGoResponseDto(postId, apiUrl);
     }
+
+    // 알림 생성 및 전송
+    @Transactional
+    public void sendNotification(User user, Post post, NotificationType type, String message) {
+      Notification notification = Notification.builder()
+          .user(user)
+          .post(post)
+          .type(type)
+          .message(message)
+          .build();
+
+      notificationRepository.save(notification);
+
+      // 실시간 전송
+      SseEmitter emitter = emitters.get(user.getId());
+      if (emitter != null) {
+        try {
+          emitter.send(SseEmitter.event()
+              .name("notification")
+              .data(notification));
+        } catch (Exception e) {
+          // 전송 실패 시 연결 종료 및 제거
+          emitters.remove(user.getId());
+        }
+      }
+    }
 }

src/main/java/com/back/domain/post/comment/service/CommentService.java

@@ -1,5 +1,7 @@
 package com.back.domain.post.comment.service;
 
+import com.back.domain.notification.enums.NotificationType;
+import com.back.domain.notification.service.NotificationService;
 import com.back.domain.post.comment.dto.request.CommentCreateRequestDto;
 import com.back.domain.post.comment.dto.request.CommentUpdateRequestDto;
 import com.back.domain.post.comment.dto.response.CommentResponseDto;
@@ -21,6 +23,7 @@ public class CommentService {
 
   private final CommentRepository commentRepository;
   private final PostRepository postRepository;
+  private final NotificationService notificationService;
   private final Rq rq;
 
   // 댓글 작성 로직
@@ -37,6 +40,14 @@ public CommentResponseDto createComment(Long postId, CommentCreateRequestDto req
         .content(reqBody.content())
         .build();
 
+    // 게시글 작성자에게 알림 전송
+    notificationService.sendNotification(
+        post.getUser(),
+        post,
+        NotificationType.COMMENT,
+        user.getNickname() + " 님이 댓글을 남겼습니다."
+    );
+
     return new CommentResponseDto(commentRepository.save(comment));
   }
 

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

@@ -1,5 +1,7 @@
 package com.back.domain.post.post.service;
 
+import com.back.domain.notification.enums.NotificationType;
+import com.back.domain.notification.service.NotificationService;
 import com.back.domain.post.category.entity.Category;
 import com.back.domain.post.category.repository.CategoryRepository;
 import com.back.domain.post.post.dto.request.PostCreateRequestDto;
@@ -31,6 +33,7 @@ public class PostService {
   private final CategoryRepository categoryRepository;
   private final TagRepository tagRepository;
   private final PostLikeRepository postLikeRepository;
+  private final NotificationService notificationService;
   private final Rq rq;
 
   // 게시글 작성 로직
@@ -134,6 +137,7 @@ public void deletePost(Long postId) {
 //    postRepository.delete(post);
   }
 
+  // 게시글 추천(좋아요) 토글 로직
   @Transactional
   public void toggleLike(Long postId) {
     User user = rq.getActor(); // 현재 로그인한 사용자
@@ -158,6 +162,14 @@ public void toggleLike(Long postId) {
       postLikeRepository.save(postLike);
       post.increaseLikeCount();
     }
+
+    // 게시글 작성자에게 알림 전송
+    notificationService.sendNotification(
+        post.getUser(),
+        post,
+        NotificationType.LIKE,
+        user.getNickname() + " 님이 추천을 남겼습니다."
+    );
   }
 
   // 태그 추가 메서드