feat : 옵저버 패턴 기반 재고 알림 서비스 추가 (사용자 이메일로 전송)

src/main/java/com/fastcampus/book_bot/domain/noti/NotificationLogs.java

@@ -0,0 +1,59 @@
+package com.fastcampus.book_bot.domain.noti;
+
+import com.fastcampus.book_bot.domain.book.Book;
+import com.fastcampus.book_bot.domain.user.User;
+import jakarta.persistence.*;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import org.springframework.data.annotation.CreatedDate;
+
+import java.time.LocalDateTime;
+
+@Entity
+@Table(name = "notification_logs")
+@Getter
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class NotificationLogs {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Integer id;
+
+    @Column(name = "sub_id", nullable = false)
+    private Integer subId;
+
+    @Column(name = "user_id", nullable = false)
+    private Integer userId;
+
+    @Column(name = "book_id", nullable = false)
+    private Integer bookId;
+
+    @Column(name = "threshold_quantity", nullable = false)
+    private Integer thresholdQuantity;
+
+    @Column(name = "current_stock", nullable = false)
+    private Integer currentStock;
+
+    @Column(name = "message", nullable = false, columnDefinition = "TEXT")
+    private String message;
+
+    @CreatedDate
+    @Column(name = "sent_at", updatable = false)
+    private LocalDateTime sentAt;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "sub_id", insertable = false, updatable = false)
+    private NotificationSub notificationSub;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "user_id", insertable = false, updatable = false)
+    private User user;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "book_id", insertable = false, updatable = false)
+    private Book book;
+}

src/main/java/com/fastcampus/book_bot/domain/noti/NotificationSub.java

@@ -0,0 +1,55 @@
+package com.fastcampus.book_bot.domain.noti;
+
+import com.fastcampus.book_bot.domain.book.Book;
+import com.fastcampus.book_bot.domain.user.User;
+import jakarta.persistence.*;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import org.springframework.data.annotation.CreatedDate;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+@Entity
+@Table(name = "notification_sub")
+@Getter
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class NotificationSub {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Integer id;
+
+    @Column(name = "user_id", nullable = false)
+    private Integer userId;
+
+    @Column(name = "book_id", nullable = false)
+    private Integer bookId;
+
+    @Column(name = "threshold_quantity", nullable = false)
+    @Builder.Default
+    private Integer thresholdQuantity = 5;
+
+    @Column(name = "is_active", nullable = false)
+    @Builder.Default
+    private Boolean isActive = true;
+
+    @CreatedDate
+    @Column(name = "created_at", updatable = false)
+    private LocalDateTime createdAt;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "user_id", insertable = false, updatable = false)
+    private User user;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "book_id", insertable = false, updatable = false)
+    private Book book;
+
+    @OneToMany(mappedBy = "notificationSub", cascade = CascadeType.ALL, orphanRemoval = true)
+    private List<NotificationLogs> notificationLogs;
+}

src/main/java/com/fastcampus/book_bot/repository/BookRepository.java

@@ -4,7 +4,11 @@
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Modifying;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Transactional;
 
 import java.util.Optional;
 
@@ -17,4 +21,7 @@ public interface BookRepository extends JpaRepository<Book, Integer> {
     Page<Book> findByBookPublisherContaining(String bookPublisher, Pageable pageable);
     Page<Book> findByBookNameContainingOrBookAuthorContainingOrBookPublisherContaining(String bookTitle, String bookAuthor, String bookPublisher, Pageable pageable);
 
+    @Modifying
+    @Query("UPDATE Book b SET b.bookQuantity = :newQuantity WHERE b.bookId = :bookId")
+    void updateBookQuantity(@Param("bookId") Integer bookId, @Param("newQuantity") Integer newQuantity);
 }

src/main/java/com/fastcampus/book_bot/repository/NotificationSubRepository.java

@@ -0,0 +1,10 @@
+package com.fastcampus.book_bot.repository;
+
+import com.fastcampus.book_bot.domain.noti.NotificationSub;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.util.List;
+
+public interface NotificationSubRepository extends JpaRepository<NotificationSub, Integer> {
+    List<NotificationSub> findActiveByBookIdAndThresholdQuantity(Integer bookId, Integer thresholdQuantity);
+}

src/main/java/com/fastcampus/book_bot/service/auth/MailService.java

@@ -13,6 +13,8 @@
 import org.thymeleaf.context.Context;
 
 import java.time.Duration;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
 import java.util.Map;
 import java.util.Random;
 
@@ -124,4 +126,37 @@ public boolean verifyCode(String userEmail, String inputCode) {
             );
         }
     }
+
+    /**
+     * 재고 알림 이메일 발송
+     * @param userEmail 사용자 이메일
+     * @param bookTitle 도서 제목
+     * @param currentStock 현재 재고
+     * @param message 알림 메시지
+     */
+    public void sendStockNotification(String userEmail, String bookTitle, int currentStock, String message) {
+        MimeMessage mimeMessage = javaMailSender.createMimeMessage();
+
+        try {
+            MimeMessageHelper messageHelper = new MimeMessageHelper(mimeMessage, true, "UTF-8");
+            messageHelper.setTo(userEmail);
+            messageHelper.setSubject("📚 재고 알림 - " + bookTitle);
+
+            Context context = new Context();
+            context.setVariable("bookTitle", bookTitle);
+            context.setVariable("currentStock", currentStock);
+            context.setVariable("message", message);
+            context.setVariable("notificationTime", LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy년 MM월 dd일 HH:mm")));
+
+            String htmlContent = templateEngine.process("notification/stock-alert", context);
+            messageHelper.setText(htmlContent, true);
+
+            javaMailSender.send(mimeMessage);
+            log.info("재고 알림 이메일 발송 성공 - 수신자: {}, 도서: {}, 재고: {}권", userEmail, bookTitle, currentStock);
+
+        } catch (Exception e) {
+            log.error("재고 알림 이메일 발송 실패 - 수신자: {}, 도서: {}", userEmail, bookTitle, e);
+            throw new RuntimeException("재고 알림 이메일 발송에 실패했습니다.", e);
+        }
+    }
 }

src/main/java/com/fastcampus/book_bot/service/grade/GradeCacheService.java

@@ -4,16 +4,19 @@
 import com.fastcampus.book_bot.dto.grade.GradeInfo;
 import com.fastcampus.book_bot.repository.UserGradeRepository;
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
 import java.math.BigDecimal;
 import java.time.Duration;
+import java.util.LinkedHashMap;
 import java.util.Set;
 
 @Service
 @RequiredArgsConstructor
+@Slf4j
 public class GradeCacheService {
 
     private final RedisTemplate<String, Object> redisTemplate;
@@ -22,36 +25,77 @@ public class GradeCacheService {
     private static final String GRADE_CACHE_KEY = "grade:";
     private static final Duration CACHE_TTL = Duration.ofHours(24);
 
-    @Transactional
+    @Transactional(readOnly = true)
     public GradeInfo getGradeInfo(String gradeName) {
-
         String cacheKey = GRADE_CACHE_KEY + gradeName;
 
-        // Redis 조회
-        GradeInfo cached = (GradeInfo) redisTemplate.opsForValue().get(cacheKey);
-        if (cached != null) {
-            return cached;
+        try {
+            // Redis 조회
+            Object cachedValue = redisTemplate.opsForValue().get(cacheKey);
+
+            if (cachedValue != null) {
+                // LinkedHashMap인 경우 GradeInfo 객체로 변환
+                if (cachedValue instanceof LinkedHashMap) {
+                    LinkedHashMap<String, Object> map = (LinkedHashMap<String, Object>) cachedValue;
+                    return mapToGradeInfo(map);
+                }
+                // 이미 GradeInfo 객체인 경우
+                else if (cachedValue instanceof GradeInfo) {
+                    return (GradeInfo) cachedValue;
+                }
+            }
+        } catch (Exception e) {
+            log.warn("Redis에서 등급 정보 조회 실패: {}, DB에서 조회합니다.", gradeName, e);
         }
 
-        // 캐시에 없으면 DB에서 조회 후 캐시 저장
+        // 캐시에 없거나 오류 발생 시 DB에서 조회
         return userGradeRepository.findByGradeName(gradeName)
                 .map(this::convertToGradeInfo)
                 .map(gradeInfo -> {
-                    redisTemplate.opsForValue().set(cacheKey, gradeInfo, CACHE_TTL);
+                    try {
+                        redisTemplate.opsForValue().set(cacheKey, gradeInfo, CACHE_TTL);
+                    } catch (Exception e) {
+                        log.warn("Redis 캐시 저장 실패: {}", gradeName, e);
+                    }
                     return gradeInfo;
                 })
                 .orElse(getDefaultGradeInfo());
-
     }
 
     public void evictGradeCache(String gradeName) {
-        redisTemplate.delete(GRADE_CACHE_KEY + gradeName);
+        try {
+            redisTemplate.delete(GRADE_CACHE_KEY + gradeName);
+        } catch (Exception e) {
+            log.warn("Redis 캐시 삭제 실패: {}", gradeName, e);
+        }
     }
 
     public void evictAllGradeCache() {
-        Set<String> keys = redisTemplate.keys(GRADE_CACHE_KEY + "*");
-        if (keys != null && !keys.isEmpty()) {
-            redisTemplate.delete(keys);
+        try {
+            Set<String> keys = redisTemplate.keys(GRADE_CACHE_KEY + "*");
+            if (keys != null && !keys.isEmpty()) {
+                redisTemplate.delete(keys);
+            }
+        } catch (Exception e) {
+            log.warn("Redis 전체 캐시 삭제 실패", e);
+        }
+    }
+
+    // LinkedHashMap을 GradeInfo로 변환하는 헬퍼 메서드
+    private GradeInfo mapToGradeInfo(LinkedHashMap<String, Object> map) {
+        try {
+            return GradeInfo.builder()
+                    .gradeName((String) map.get("gradeName"))
+                    .minUsage(map.get("minUsage") != null ? ((Number) map.get("minUsage")).intValue() : 0)
+                    .orderCount(map.get("orderCount") != null ? ((Number) map.get("orderCount")).intValue() : 0)
+                    .discount(map.get("discount") != null ?
+                            new BigDecimal(map.get("discount").toString()) : BigDecimal.ZERO)
+                    .mileageRate(map.get("mileageRate") != null ?
+                            new BigDecimal(map.get("mileageRate").toString()) : BigDecimal.ZERO)
+                    .build();
+        } catch (Exception e) {
+            log.error("LinkedHashMap을 GradeInfo로 변환 실패: {}", map, e);
+            return getDefaultGradeInfo();
         }
     }
 
@@ -60,8 +104,10 @@ private GradeInfo convertToGradeInfo(UserGrade userGrade) {
                 .gradeName(userGrade.getGradeName())
                 .minUsage(userGrade.getMinUsage())
                 .orderCount(userGrade.getOrderCount())
-                .discount(userGrade.getDiscount())
-                .mileageRate(userGrade.getMileageRate())
+                .discount(userGrade.getDiscount() != null ?
+                        userGrade.getDiscount() : BigDecimal.ZERO)
+                .mileageRate(userGrade.getMileageRate() != null ?
+                        userGrade.getMileageRate() : BigDecimal.ZERO)
                 .build();
     }
 
@@ -70,8 +116,8 @@ private GradeInfo getDefaultGradeInfo() {
                 .gradeName("BRONZE")
                 .minUsage(100)
                 .orderCount(1)
-                .discount(BigDecimal.valueOf(0.0))
-                .mileageRate(BigDecimal.valueOf(0.0))
+                .discount(BigDecimal.ZERO)
+                .mileageRate(BigDecimal.ZERO)
                 .build();
     }
-}
+}