feat/#71: 학생 알림 조회 기능 구현

src/main/java/com/campus/campus/domain/council/domain/entity/CouncilType.java

@@ -10,17 +10,21 @@ public boolean hasAccess(User user, StudentCouncil writer) {
 				user.getSchool().getSchoolId().equals(writer.getSchool().getSchoolId());
 		}
 
-		@Override public String topic(StudentCouncil writer) {
+		@Override
+		public String topic(StudentCouncil writer) {
 			return "school_" + writer.getSchool().getSchoolId();
 		}
+
 	},
 	COLLEGE_COUNCIL {
 		@Override
 		public boolean hasAccess(User user, StudentCouncil writer) {
 			return user.getCollege() != null &&
 				user.getCollege().getCollegeId().equals(writer.getCollege().getCollegeId());
 		}
-		@Override public String topic(StudentCouncil writer) {
+
+		@Override
+		public String topic(StudentCouncil writer) {
 			return "college_" + writer.getCollege().getCollegeId();
 		}
 	},
@@ -30,11 +34,16 @@ public boolean hasAccess(User user, StudentCouncil writer) {
 			return user.getMajor() != null &&
 				user.getMajor().getMajorId().equals(writer.getMajor().getMajorId());
 		}
-		@Override public String topic(StudentCouncil writer) {
+
+		@Override
+		public String topic(StudentCouncil writer) {
 			return "major_" + writer.getMajor().getMajorId();
 		}
+
 	};
 
 	public abstract boolean hasAccess(User user, StudentCouncil writer);
+
 	public abstract String topic(StudentCouncil writer);
+
 }

src/main/java/com/campus/campus/domain/councilpost/application/CouncilPostPushListener.java

@@ -9,6 +9,7 @@
 
 import com.campus.campus.domain.councilpost.application.dto.request.CouncilPostCreatedEvent;
 import com.campus.campus.domain.councilpost.domain.entity.PostCategory;
+import com.campus.campus.domain.notification.application.service.NotificationService;
 import com.campus.campus.global.firebase.application.service.FirebaseCloudMessageService;
 
 import lombok.RequiredArgsConstructor;
@@ -25,6 +26,7 @@ public class CouncilPostPushListener {
 	private static final String DATA_KEY_CATEGORY = "category";
 
 	private final FirebaseCloudMessageService firebaseCloudMessageService;
+	private final NotificationService notificationService;
 
 	@Async
 	@TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
@@ -36,6 +38,8 @@ public void handleCouncilPostCreatedEvent(CouncilPostCreatedEvent event) {
 		log.info("[PUSH] after_commit event received. topic={}, postId={}, category={}",
 			event.topic(), event.postId(), event.category());
 
+		notificationService.savePostCreatedNotification(event, title, body);
+
 		firebaseCloudMessageService.sendToTopic(
 			event.topic(),
 			title,

src/main/java/com/campus/campus/domain/notification/application/dto/CursorResponse.java

@@ -0,0 +1,9 @@
+package com.campus.campus.domain.notification.application.dto;
+
+import java.util.List;
+
+public record CursorResponse<T>(
+	List<T> items,
+	NextCursor nextCursor,
+	boolean hasNext
+) {}

src/main/java/com/campus/campus/domain/notification/application/dto/NextCursor.java

@@ -0,0 +1,8 @@
+package com.campus.campus.domain.notification.application.dto;
+
+import java.time.LocalDateTime;
+
+public record NextCursor(
+	LocalDateTime createdAt,
+	Long id
+) {}

src/main/java/com/campus/campus/domain/notification/application/dto/NotificationResponse.java

@@ -0,0 +1,29 @@
+package com.campus.campus.domain.notification.application.dto;
+
+import com.campus.campus.domain.notification.domain.entity.NotificationType;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+public record NotificationResponse(
+	@Schema(description = "알림 ID", example = "1")
+	Long id,
+
+	@Schema(description = "알림 타입", example = "COUNCIL_POST_CREATED")
+	NotificationType type,
+
+	@Schema(description = "알림 제목", example = "총학생회")
+	String title,
+
+	@Schema(description = "알림 내용", example = "새 행사글이 등록되었습니다.")
+	String body,
+
+	@Schema(description = "참조 ID (게시글 ID 등)", example = "123")
+	Long referenceId,
+
+	@Schema(description = "읽음 여부", example = "false")
+	boolean isRead,
+
+	@Schema(description = "생성 시각 (상대 시간)", example = "5분 전")
+	String createTimeBeforeNow
+) {
+}

src/main/java/com/campus/campus/domain/notification/application/exception/ErrorCode.java

@@ -0,0 +1,21 @@
+package com.campus.campus.domain.notification.application.exception;
+
+import org.springframework.http.HttpStatus;
+
+import com.campus.campus.global.common.exception.ErrorCodeInterface;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public enum ErrorCode implements ErrorCodeInterface {
+
+	NOTIFICATION_NOT_FOUND(2801, HttpStatus.NOT_FOUND, "알림을 찾을 수 없습니다."),
+	NOTIFICATION_ACCESS_DENIED(2802, HttpStatus.FORBIDDEN, "해당 알림에 접근할 권한이 없습니다."),
+	INVALID_NOTIFICATION_IDS(2803, HttpStatus.BAD_REQUEST, "유효하지 않은 알림 ID 목록입니다.");
+
+	private final int code;
+	private final HttpStatus status;
+	private final String message;
+}

src/main/java/com/campus/campus/domain/notification/application/exception/NotificationAccessDeniedException.java

@@ -0,0 +1,9 @@
+package com.campus.campus.domain.notification.application.exception;
+
+import com.campus.campus.global.common.exception.ApplicationException;
+
+public class NotificationAccessDeniedException extends ApplicationException {
+	public NotificationAccessDeniedException() {
+		super(ErrorCode.NOTIFICATION_ACCESS_DENIED);
+	}
+}

src/main/java/com/campus/campus/domain/notification/application/exception/NotificationNotFoundException.java

@@ -0,0 +1,9 @@
+package com.campus.campus.domain.notification.application.exception;
+
+import com.campus.campus.global.common.exception.ApplicationException;
+
+public class NotificationNotFoundException extends ApplicationException {
+	public NotificationNotFoundException() {
+		super(ErrorCode.NOTIFICATION_NOT_FOUND);
+	}
+}

src/main/java/com/campus/campus/domain/notification/application/mapper/NotificationMapper.java

@@ -0,0 +1,41 @@
+package com.campus.campus.domain.notification.application.mapper;
+
+import org.springframework.stereotype.Component;
+
+import com.campus.campus.domain.notification.application.dto.NotificationResponse;
+import com.campus.campus.domain.notification.domain.entity.Notification;
+import com.campus.campus.domain.notification.domain.entity.NotificationType;
+import com.campus.campus.domain.notification.util.TimeFormatter;
+import com.campus.campus.domain.user.domain.entity.User;
+
+import lombok.RequiredArgsConstructor;
+
+@Component
+@RequiredArgsConstructor
+public class NotificationMapper {
+
+	private final TimeFormatter timeFormatter;
+
+	public NotificationResponse toResponse(Notification notification) {
+		return new NotificationResponse(
+			notification.getId(),
+			notification.getType(),
+			notification.getTitle(),
+			notification.getBody(),
+			notification.getReferenceId(),
+			notification.isRead(),
+			timeFormatter.formatRelativeTime(notification.getCreatedAt())
+		);
+	}
+
+	public Notification createNotification(User user, NotificationType type,
+		String title, String body, Long referenceId) {
+		return Notification.builder()
+			.user(user)
+			.type(type)
+			.title(title)
+			.body(body)
+			.referenceId(referenceId)
+			.build();
+	}
+}

src/main/java/com/campus/campus/domain/notification/application/service/NotificationService.java

@@ -0,0 +1,122 @@
+package com.campus.campus.domain.notification.application.service;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Propagation;
+import org.springframework.transaction.annotation.Transactional;
+
+import com.campus.campus.domain.councilpost.application.dto.request.CouncilPostCreatedEvent;
+import com.campus.campus.domain.notification.application.dto.CursorResponse;
+import com.campus.campus.domain.notification.application.dto.NextCursor;
+import com.campus.campus.domain.notification.application.dto.NotificationResponse;
+import com.campus.campus.domain.notification.application.exception.NotificationAccessDeniedException;
+import com.campus.campus.domain.notification.application.exception.NotificationNotFoundException;
+import com.campus.campus.domain.notification.application.mapper.NotificationMapper;
+import com.campus.campus.domain.notification.domain.entity.Notification;
+import com.campus.campus.domain.notification.domain.entity.NotificationType;
+import com.campus.campus.domain.notification.domain.repository.NotificationRepository;
+import com.campus.campus.domain.user.application.exception.UserNotFoundException;
+import com.campus.campus.domain.user.domain.entity.User;
+import com.campus.campus.domain.user.domain.repository.UserRepository;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class NotificationService {
+
+	private final NotificationRepository notificationRepository;
+	private final NotificationMapper notificationMapper;
+	private final UserRepository userRepository;
+
+	public CursorResponse<NotificationResponse> getNotificationsByCursor(
+		Long userId,
+		LocalDateTime cursorCreatedAt,
+		Long cursorId,
+		int limit
+	) {
+		User user = userRepository.findByIdAndDeletedAtIsNull(userId)
+			.orElseThrow(UserNotFoundException::new);
+
+		int pageSize = Math.min(Math.max(limit, 1), 50);
+		Pageable pageable = PageRequest.of(0, pageSize);
+
+		boolean isFirst = (cursorCreatedAt == null || cursorId == null);
+
+		List<Notification> list = isFirst
+			? notificationRepository.findByUserOrderByCreatedAtDescIdDesc(user, pageable)
+			: notificationRepository.findNextByCursor(user, cursorCreatedAt, cursorId, pageable);
+
+		List<NotificationResponse> items = list.stream()
+			.map(notificationMapper::toResponse)
+			.toList();
+
+		boolean hasNext = list.size() == pageSize;
+
+		NextCursor nextCursor = null;
+		if (!list.isEmpty()) {
+			Notification last = list.get(list.size() - 1);
+			nextCursor = new NextCursor(last.getCreatedAt(), last.getId());
+		}
+
+		return new CursorResponse<>(items, nextCursor, hasNext);
+	}
+
+	@Transactional
+	public void markAsRead(Long userId, Long notificationId) {
+		User user = userRepository.findByIdAndDeletedAtIsNull(userId)
+			.orElseThrow(UserNotFoundException::new);
+
+		Notification notification = notificationRepository.findById(notificationId)
+			.orElseThrow(NotificationNotFoundException::new);
+
+		if (!notification.getUser().getId().equals(user.getId())) {
+			throw new NotificationAccessDeniedException();
+		}
+
+		notification.markAsRead();
+	}
+
+	@Transactional(propagation = Propagation.REQUIRES_NEW)
+	public void savePostCreatedNotification(CouncilPostCreatedEvent event, String title, String body) {
+
+		List<User> targetUsers = findUsersByTopic(event.topic());
+
+		List<Notification> notifications = targetUsers.stream()
+			.map(user -> notificationMapper.createNotification(
+				user,
+				NotificationType.COUNCIL_POST_CREATED,
+				title,
+				body,
+				event.postId()
+			))
+			.toList();
+
+		notificationRepository.saveAll(notifications);
+	}
+
+	@Transactional(readOnly = true)
+	public boolean hasUnread(Long userId) {
+		return notificationRepository.existsByUser_IdAndIsReadFalse(userId);
+	}
+
+	private List<User> findUsersByTopic(String topic) {
+
+		String[] parts = topic.split("_");
+		String scope = parts[0];
+		Long scopeId = Long.valueOf(parts[1]);
+
+		return switch (scope) {
+			case "major" -> userRepository.findAllByMajor_MajorIdAndDeletedAtIsNull(scopeId);
+			case "college" -> userRepository.findAllByCollege_CollegeIdAndDeletedAtIsNull(scopeId);
+			case "school" -> userRepository.findAllBySchool_SchoolIdAndDeletedAtIsNull(scopeId);
+			default -> List.of();
+		};
+	}
+}

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

@@ -0,0 +1,69 @@
+package com.campus.campus.domain.notification.domain.entity;
+
+import java.time.LocalDateTime;
+
+import com.campus.campus.domain.user.domain.entity.User;
+import com.campus.campus.global.entity.BaseEntity;
+
+import jakarta.persistence.Column;
+import jakarta.persistence.Entity;
+import jakarta.persistence.EnumType;
+import jakarta.persistence.Enumerated;
+import jakarta.persistence.FetchType;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+import jakarta.persistence.JoinColumn;
+import jakarta.persistence.ManyToOne;
+import lombok.AccessLevel;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Entity
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+public class Notification extends BaseEntity {
+
+	@Id
+	@GeneratedValue(strategy = GenerationType.IDENTITY)
+	private Long id;
+
+	@ManyToOne(fetch = FetchType.LAZY)
+	@JoinColumn(name = "user_id", nullable = false)
+	private User user;
+
+	@Enumerated(EnumType.STRING)
+	@Column(nullable = false)
+	private NotificationType type;
+
+	@Column(nullable = false)
+	private String title;
+
+	@Column(nullable = false)
+	private String body;
+
+	@Column(name = "reference_id")
+	private Long referenceId; // postId, commentId 등
+
+	@Column(nullable = false)
+	private boolean isRead = false;
+
+	@Column(name = "read_at")
+	private LocalDateTime readAt;
+
+	@Builder
+	public Notification(User user, NotificationType type, String title,
+		String body, Long referenceId) {
+		this.user = user;
+		this.type = type;
+		this.title = title;
+		this.body = body;
+		this.referenceId = referenceId;
+	}
+
+	public void markAsRead() {
+		this.isRead = true;
+		this.readAt = LocalDateTime.now();
+	}
+}

src/main/java/com/campus/campus/domain/notification/domain/entity/NotificationType.java

@@ -0,0 +1,6 @@
+package com.campus.campus.domain.notification.domain.entity;
+
+public enum NotificationType {
+	COUNCIL_POST_CREATED,
+	SYSTEM_NOTICE
+}