[feat] 알림 목록 조회 기능 구현 #70

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

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+package com.back.domain.notification.controller;
+
+import com.back.domain.notification.dto.NotificationGoResponseDto;
+import com.back.domain.notification.dto.NotificationListResponseDto;
+import com.back.domain.notification.service.NotificationService;
+import com.back.global.rsData.RsData;
+import jakarta.validation.constraints.Max;
+import jakarta.validation.constraints.Min;
+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;
+
+@RestController
+@RequestMapping("/api/me")
+@RequiredArgsConstructor
+@Validated
+public class NotificationController {
+
+    private final NotificationService notificationService;
+
+    @GetMapping("/notifications")
+    public RsData<NotificationListResponseDto> getNotifications(
+            @AuthenticationPrincipal(expression = "id") Long userId,
+            @RequestParam(required = false) @DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME) LocalDateTime lastCreatedAt,
+            @RequestParam(required = false) Long lastId,
+            @RequestParam(defaultValue = "20") @Min(1) @Max(100) int limit
+    ) {
+        NotificationListResponseDto body = notificationService.getNotifications(userId, lastCreatedAt, lastId, limit);
+        return RsData.successOf(body);
+    }
+
+    @PostMapping("/notifications/{id}")
+    public RsData<NotificationGoResponseDto> goPostLink(
+            @AuthenticationPrincipal(expression = "id") Long userId,
+            @PathVariable("id") Long notificationId
+    ) {
+        var body = notificationService.markAsReadAndGetPostLink(userId, notificationId);
+        return RsData.successOf(body);
+    }
+}

src/main/java/com/back/domain/notification/dto/NotificationGoResponseDto.java

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+package com.back.domain.notification.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class NotificationGoResponseDto {
+    private Long postId;
+    private String postApiUrl;
+}
+

src/main/java/com/back/domain/notification/dto/NotificationItemDto.java

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+package com.back.domain.notification.dto;
+
+import com.back.domain.notification.entity.Notification;
+import com.back.domain.notification.enums.NotificationType;
+import java.time.LocalDateTime;
+import lombok.Builder;
+import lombok.Getter;
+
+@Getter
+@Builder
+public class NotificationItemDto {
+    private Long id;
+    private NotificationType type;
+    private Long postId;
+    private String postTitle;
+    private boolean read;
+    private LocalDateTime createdAt;
+
+    public static NotificationItemDto from(Notification n) {
+        return NotificationItemDto.builder()
+                .id(n.getId())
+                .type(n.getType())
+                .postId(n.getPost().getId())
+                .postTitle(n.getPost().getTitle())
+                .read(n.isRead())
+                .createdAt(n.getCreatedAt())
+                .build();
+    }
+}
+

src/main/java/com/back/domain/notification/dto/NotificationListResponseDto.java

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+package com.back.domain.notification.dto;
+
+import java.time.LocalDateTime;
+import java.util.List;
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class NotificationListResponseDto {
+    private List<NotificationItemDto> items;
+    private boolean hasNext;
+    private LocalDateTime nextCreatedAt;
+    private Long nextId;
+}
+

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

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+package com.back.domain.notification.entity;
+
+import com.back.domain.notification.enums.NotificationType;
+import com.back.domain.post.post.entity.Post;
+import com.back.domain.user.entity.User;
+import jakarta.persistence.*;
+import lombok.*;
+import org.springframework.data.annotation.CreatedDate;
+import org.springframework.data.jpa.domain.support.AuditingEntityListener;
+
+import java.time.LocalDateTime;
+
+@Entity
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+@AllArgsConstructor
+@Builder
+@EntityListeners(AuditingEntityListener.class)
+public class Notification {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "user_id", nullable = false)
+    private User user;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "post_id", nullable = false)
+    private Post post;
+
+    @Enumerated(EnumType.STRING)
+    @Column(name = "type", nullable = false, length = 20)
+    private NotificationType type;
+
+    @Builder.Default
+    @Column(name = "is_read", nullable = false) //read는 DB 예약어 충돌 가능성 있어 @Column(name = "is_read") 설정
+    private boolean read = false;
+
+    @CreatedDate
+    @Column(name = "created_at", nullable = false, updatable = false)
+    private LocalDateTime createdAt;
+
+    public void markRead() {
+        this.read = true;
+    }
+}

src/main/java/com/back/domain/notification/enums/NotificationType.java

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+package com.back.domain.notification.enums;
+
+public enum NotificationType {
+    COMMENT,
+    LIKE
+}
+

src/main/java/com/back/domain/notification/repository/NotificationRepository.java

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+package com.back.domain.notification.repository;
+
+import com.back.domain.notification.entity.Notification;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+import org.springframework.stereotype.Repository;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+@Repository
+public interface NotificationRepository extends JpaRepository<Notification, Long> {
+
+    @Query("""
+        select n from Notification n
+         where n.user.id = :userId
+         order by n.createdAt desc, n.id desc
+    """)
+    List<Notification> findMyNotificationsFirstPage(@Param("userId") Long userId,
+                                                    Pageable pageable);
+
+    @Query("""
+        select n from Notification n
+         where n.user.id = :userId
+           and (n.createdAt < :lastCreatedAt or (n.createdAt = :lastCreatedAt and n.id < :lastId))
+         order by n.createdAt desc, n.id desc
+    """)
+    List<Notification> findMyNotificationsAfter(@Param("userId") Long userId,
+                                                @Param("lastCreatedAt") LocalDateTime lastCreatedAt,
+                                                @Param("lastId") Long lastId,
+                                                Pageable pageable);
+
+    @Query("""
+        select n from Notification n
+         where n.id = :id and n.user.id = :userId
+    """)
+    Notification findByIdAndUserId(@Param("id") Long id, @Param("userId") Long userId);
+}

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

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+package com.back.domain.notification.service;
+
+import com.back.domain.notification.dto.NotificationGoResponseDto;
+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.repository.NotificationRepository;
+import com.back.global.exception.ServiceException;
+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;
+
+@Service
+@RequiredArgsConstructor
+public class NotificationService {
+
+    private final NotificationRepository notificationRepository;
+
+    @Transactional(readOnly = true)
+    public NotificationListResponseDto getNotifications(Long userId, LocalDateTime lastCreatedAt, Long lastId, int limit) {
+        int safeLimit = Math.max(1, Math.min(limit, 100));
+        int fetchSize = safeLimit + 1;
+
+        List<Notification> rows;
+        if (lastCreatedAt == null || lastId == null) {
+            rows = notificationRepository.findMyNotificationsFirstPage(userId, PageRequest.of(0, fetchSize));
+        } else {
+            rows = notificationRepository.findMyNotificationsAfter(userId, lastCreatedAt, lastId, PageRequest.of(0, fetchSize));
+        }
+
+        boolean hasNext = rows.size() > safeLimit;
+        if (hasNext) rows = rows.subList(0, safeLimit);
+
+        List<NotificationItemDto> items = new ArrayList<>();
+        for (Notification n : rows) items.add(NotificationItemDto.from(n));
+
+        LocalDateTime nextCreatedAt = null;
+        Long nextId = null;
+        if (hasNext && !rows.isEmpty()) {
+            Notification last = rows.get(rows.size() - 1);
+            nextCreatedAt = last.getCreatedAt();
+            nextId = last.getId();
+        }
+
+        return new NotificationListResponseDto(items, hasNext, nextCreatedAt, nextId);
+    }
+
+    @Transactional
+    public NotificationGoResponseDto markAsReadAndGetPostLink(Long userId, Long notificationId) {
+        Notification notification = notificationRepository.findByIdAndUserId(notificationId, userId);
+        if (notification == null) {
+            throw new ServiceException(404, "알림을 찾을 수 없습니다.");
+        }
+        if (!notification.isRead()) {
+            notification.markRead();
+        }
+        Long postId = notification.getPost().getId();
+        String apiUrl = "/api/posts/" + postId;
+        return new NotificationGoResponseDto(postId, apiUrl);
+    }
+}