[Feat/OPS-389] 스페이스 초대 알림 구현 (#136)

* new : emitter 관리 service, controller 생성

* feat : 하트비트 로직 구현

* fix : 비동기 처리 하도록 변경

* feat : 관련 테스트 케이스 추가

* fix : 테스트 수정

* fix : 불필요한 어노테이션 삭제

---------

Co-authored-by: EpicFn <[email protected]>

Author: EpicFn

src/main/java/org/tuna/zoopzoop/backend/BackendApplication.java

@@ -3,9 +3,11 @@
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.data.jpa.repository.config.EnableJpaAuditing;
+import org.springframework.scheduling.annotation.EnableScheduling;
 
 @SpringBootApplication
 @EnableJpaAuditing
+@EnableScheduling
 public class BackendApplication {
     public static void main(String[] args) {
         SpringApplication.run(BackendApplication.class, args);

src/main/java/org/tuna/zoopzoop/backend/domain/SSE/controller/ApiV1NotificationController.java

@@ -0,0 +1,34 @@
+package org.tuna.zoopzoop.backend.domain.SSE.controller;
+
+import lombok.RequiredArgsConstructor;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+import org.tuna.zoopzoop.backend.domain.SSE.service.EmitterService;
+import org.tuna.zoopzoop.backend.global.security.jwt.CustomUserDetails;
+
+@RestController
+@RequestMapping("/api/v1/notifications")
+@RequiredArgsConstructor
+public class ApiV1NotificationController {
+    private final EmitterService emitterService;
+
+    /**
+     * SSE 구독 엔드포인트
+     * @param userDetails - 현재 인증된 사용자 정보
+     * @return SseEmitter - 클라이언트와의 SSE 연결을 관리하는 객체
+     */
+    @GetMapping(value = "/subscribe", produces = "text/event-stream")
+    public SseEmitter subscribe(
+            @AuthenticationPrincipal CustomUserDetails userDetails
+    ) {
+        // 1. 현재 로그인한 사용자의 ID를 가져옴
+        Long memberId = (long) userDetails.getMember().getId();
+
+        // 2. EmitterService를 통해 Emitter를 생성하고 반환
+        return emitterService.addEmitter(memberId);
+    }
+}

src/main/java/org/tuna/zoopzoop/backend/domain/SSE/service/EmitterService.java

@@ -0,0 +1,75 @@
+package org.tuna.zoopzoop.backend.domain.SSE.service;
+
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Service;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+@Service
+public class EmitterService {
+    // 1. 모든 Emitter를 저장하는 ConcurrentHashMap
+    private final Map<Long, SseEmitter> emitters = new ConcurrentHashMap<>();
+
+    /**
+     * 새로운 Emitter 생성 및 저장
+     * @param memberId - 사용자 ID
+     * @return SseEmitter - 생성된 Emitter 객체
+     */
+    public SseEmitter addEmitter(Long memberId) {
+        // 1시간 타임아웃 설정
+        SseEmitter emitter = new SseEmitter(3600L * 1000);
+        this.emitters.put(memberId, emitter);
+
+        // Emitter 완료 또는 타임아웃 시 Map에서 삭제
+        emitter.onCompletion(() -> this.emitters.remove(memberId));
+        emitter.onTimeout(() -> this.emitters.remove(memberId));
+
+        // 503 에러 방지를 위한 더미 이벤트 전송
+        try {
+            emitter.send(SseEmitter.event().name("connect").data("SSE connected!"));
+        } catch (IOException e) {
+            // 예외 처리
+        }
+
+        return emitter;
+    }
+
+    /**
+     * 특정 사용자에게 이벤트 전송
+     * @param memberId - 사용자 ID
+     * @param eventName - 이벤트 이름
+     * @param data - 전송할 데이터 객체
+     */
+    public void sendNotification(Long memberId, String eventName, Object data) {
+        SseEmitter emitter = this.emitters.get(memberId);
+        if (emitter != null) {
+            try {
+                // data 객체를 JSON 문자열로 변환하여 전송해야 함 (Controller에서는 자동 변환)
+                emitter.send(SseEmitter.event().name(eventName).data(data));
+            } catch (IOException e) {
+                this.emitters.remove(memberId);
+            }
+        }
+    }
+
+    /**
+     * 20초마다 모든 Emitter에 하트비트 전송
+     * 클라이언트와의 연결 유지를 위해 주기적으로 빈 이벤트를 전송
+     */
+    @Scheduled(fixedRate = 20000)
+    public void sendHeartbeat() {
+        // 모든 Emitter에 하트비트 전송
+        emitters.forEach((userId, emitter) -> {
+            try {
+                // SSE 주석(comment)을 사용하여 클라이언트에서 별도 이벤트를 발생시키지 않음
+                emitter.send(SseEmitter.event().comment("keep-alive"));
+            } catch (IOException e) {
+                // 전송 실패 시, 클라이언트 연결이 끊어진 것으로 간주하고 Map에서 제거
+                emitters.remove(userId);
+            }
+        });
+    }
+}

src/main/java/org/tuna/zoopzoop/backend/domain/space/membership/service/MembershipService.java

@@ -8,12 +8,15 @@
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+import org.tuna.zoopzoop.backend.domain.SSE.service.EmitterService;
 import org.tuna.zoopzoop.backend.domain.member.entity.Member;
 import org.tuna.zoopzoop.backend.domain.member.service.MemberService;
 import org.tuna.zoopzoop.backend.domain.space.membership.entity.Membership;
 import org.tuna.zoopzoop.backend.domain.space.membership.enums.Authority;
 import org.tuna.zoopzoop.backend.domain.space.membership.enums.JoinState;
 import org.tuna.zoopzoop.backend.domain.space.membership.repository.MembershipRepository;
+import org.tuna.zoopzoop.backend.domain.space.space.dto.etc.SpaceInvitationInfo;
 import org.tuna.zoopzoop.backend.domain.space.space.entity.Space;
 import org.tuna.zoopzoop.backend.global.rsData.RsData;
 
@@ -26,6 +29,7 @@
 public class MembershipService {
     private final MembershipRepository membershipRepository;
     private final MemberService memberService;
+    private final NotificationService notificationService;
 
     // ======================== 멤버십 조회 ======================== //
 
@@ -205,6 +209,7 @@ public Membership addMemberToSpace(Member member, Space space, Authority authori
      * @param invitedName 초대할 멤버 이름 목록
      * @return 생성된 Membership 엔티티 목록
      */
+    @Transactional
     public List<Membership> inviteMembersToSpace(Space space, List<String> invitedName) {
         // 1. 이름 중복 제거
         List<String> uniqueNames = invitedName.stream().distinct().toList();
@@ -228,7 +233,24 @@ public List<Membership> inviteMembersToSpace(Space space, List<String> invitedNa
                 })
                 .toList();
 
-        return membershipRepository.saveAll(invitedMemberships);
+        // 4. 멤버십 저장
+        List<Membership> savedMemberships = membershipRepository.saveAll(invitedMemberships);
+
+        // 5. 알림 전송 호출
+        savedMemberships.forEach(membership -> {
+            notificationService.sendSpaceInvitation(
+                    (long) membership.getMember().getId(),
+                        new SpaceInvitationInfo(
+                                space.getId(),
+                                space.getName(),
+                                space.getThumbnailUrl(),
+                                membership.getId()
+                    )
+            );
+        });
+
+        // 6. 저장된 멤버십 반환
+        return savedMemberships;
     }
 
     /**

src/main/java/org/tuna/zoopzoop/backend/domain/space/membership/service/NotificationService.java

@@ -0,0 +1,17 @@
+package org.tuna.zoopzoop.backend.domain.space.membership.service;
+
+import lombok.RequiredArgsConstructor;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+import org.tuna.zoopzoop.backend.domain.SSE.service.EmitterService;
+
+@Service
+@RequiredArgsConstructor
+public class NotificationService {
+    private final EmitterService emitterService;
+
+    @Async // 별도 스레드에서 비동기 실행
+    public void sendSpaceInvitation(Long memberId, Object invitationData) {
+        emitterService.sendNotification(memberId, "space-invitation", invitationData);
+    }
+}

src/main/java/org/tuna/zoopzoop/backend/domain/space/space/controller/ApiV1SpaceController.java

@@ -220,8 +220,8 @@ public RsData<ResBodyForSpaceInfo> getSpace(
     @Operation(summary = "Liveblocks 접속 토큰 발급")
     public ResponseEntity<RsData<ResBodyForAuthToken>> getAuthToken(
             @PathVariable Integer spaceId,
-            @AuthenticationPrincipal CustomUserDetails userDetails) throws AccessDeniedException {
-
+            @AuthenticationPrincipal CustomUserDetails userDetails
+    ) throws AccessDeniedException {
         Member member = userDetails.getMember();
         String token = dashboardService.getAuthTokenForSpace(spaceId, member);
 

src/test/java/org/tuna/zoopzoop/backend/domain/space/membership/service/NotificationServiceTest.java

@@ -0,0 +1,39 @@
+package org.tuna.zoopzoop.backend.domain.space.membership.service;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.tuna.zoopzoop.backend.domain.SSE.service.EmitterService;
+
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+@ExtendWith(MockitoExtension.class)
+class NotificationServiceTest {
+    @Mock
+    private EmitterService emitterService;
+
+    @InjectMocks
+    private NotificationService notificationService;
+
+    @Test
+    @DisplayName("초대 알림 전송 시 EmitterService의 sendNotification이 올바르게 호출됨")
+    void sendSpaceInvitation_CallsEmitterService() {
+        // given (준비)
+        Long memberId = 1L;
+        String testData = "test data";
+
+        // when (실행)
+        notificationService.sendSpaceInvitation(memberId, testData);
+
+        // then (검증)
+        // EmitterService의 sendNotification 메소드가
+        // memberId, "space-invitation", testData 파라미터로
+        // 1번 호출되었는지 검증
+        verify(emitterService, times(1)).sendNotification(memberId, "space-invitation", testData);
+    }
+
+}