refactor: 캐시 및 DLQ 타입 변환 로직 개선

- toLongOrNull 메서드로 통일
- 예외 throw 대신 null 반환 + 로깅
- 중복 타입 변환 코드 제거
- DlqMessage 불필요한 null 체크 제거

Author: sylee6529

apps/commerce-api/src/main/java/com/loopers/infrastructure/cache/MemberLikesCache.java

@@ -79,9 +79,10 @@ public Set<Long> findLikedProductIds(Long memberId, List<Long> productIds) {
                 return Set.of();
             }
 
-            // productIds 중 좋아요한 것만 필터링
+            // productIds 중 좋아요한 것만 필터링 (변환 실패한 값은 제외)
             Set<Long> likedSet = allLiked.stream()
-                    .map(obj -> (Long) obj)
+                    .map(this::toLongOrNull)
+                    .filter(v -> v != null)
                     .collect(Collectors.toSet());
 
             return productIds.stream()
@@ -107,7 +108,8 @@ public Set<Long> findAll(Long memberId) {
             }
 
             return members.stream()
-                    .map(obj -> (Long) obj)
+                    .map(this::toLongOrNull)
+                    .filter(v -> v != null)
                     .collect(Collectors.toSet());
 
         } catch (Exception e) {
@@ -165,4 +167,29 @@ public void delete(Long memberId) {
             log.warn("[MemberLikesCache] delete failed, error={}", e.getMessage());
         }
     }
+
+    /**
+     * Redis 값을 Long으로 변환 (변환 실패 시 null 반환)
+     */
+    private Long toLongOrNull(Object value) {
+        if (value == null) {
+            return null;
+        }
+        if (value instanceof Long) {
+            return (Long) value;
+        }
+        if (value instanceof Integer) {
+            return ((Integer) value).longValue();
+        }
+        if (value instanceof String) {
+            try {
+                return Long.parseLong((String) value);
+            } catch (NumberFormatException e) {
+                log.warn("[MemberLikesCache] Failed to parse String to Long: {}", value);
+                return null;
+            }
+        }
+        log.warn("[MemberLikesCache] Unsupported value type: {}", value.getClass().getSimpleName());
+        return null;
+    }
 }

apps/commerce-api/src/main/java/com/loopers/infrastructure/cache/ProductLikeCountCache.java

@@ -60,16 +60,7 @@ public Long get(Long productId) {
         try {
             String key = CacheKeyGenerator.productLikeCountKey(productId);
             Object value = cacheRedisTemplate.opsForValue().get(key);
-
-            if (value == null) {
-                return null;
-            }
-
-            if (value instanceof Integer) {
-                return ((Integer) value).longValue();
-            }
-
-            return (Long) value;
+            return toLongOrNull(value);
         } catch (Exception e) {
             log.warn("[ProductLikeCountCache] get failed, error={}", e.getMessage());
             return null;
@@ -109,11 +100,9 @@ public Map<Long, Long> getAllCounts() {
                     // key에서 productId 추출
                     Long productId = extractProductIdFromKey(key);
                     Object value = cacheRedisTemplate.opsForValue().get(key);
+                    Long count = toLongOrNull(value);
 
-                    if (value != null && productId != null) {
-                        Long count = value instanceof Integer
-                            ? ((Integer) value).longValue()
-                            : (Long) value;
+                    if (count != null && productId != null) {
                         result.put(productId, count);
                     }
                 } catch (Exception e) {
@@ -155,4 +144,29 @@ private Long extractProductIdFromKey(String key) {
             return null;
         }
     }
+
+    /**
+     * Redis 값을 Long으로 변환 (변환 실패 시 null 반환)
+     */
+    private Long toLongOrNull(Object value) {
+        if (value == null) {
+            return null;
+        }
+        if (value instanceof Long) {
+            return (Long) value;
+        }
+        if (value instanceof Integer) {
+            return ((Integer) value).longValue();
+        }
+        if (value instanceof String) {
+            try {
+                return Long.parseLong((String) value);
+            } catch (NumberFormatException e) {
+                log.warn("[ProductLikeCountCache] Failed to parse String to Long: {}", value);
+                return null;
+            }
+        }
+        log.warn("[ProductLikeCountCache] Unsupported value type: {}", value.getClass().getSimpleName());
+        return null;
+    }
 }

apps/commerce-streamer/src/main/java/com/loopers/domain/dlq/DlqMessage.java

@@ -103,7 +103,7 @@ public static DlqMessage create(
         dlqMessage.originalOffset = originalOffset;
         dlqMessage.messageKey = messageKey;
         dlqMessage.messageValue = messageValue;
-        dlqMessage.errorType = exception.getClass().getSimpleName();
+        dlqMessage.errorType = resolveErrorType(exception);
         dlqMessage.errorMessage = exception.getMessage();
         dlqMessage.stackTrace = getStackTraceAsString(exception);
         dlqMessage.failedAt = ZonedDateTime.now();
@@ -138,4 +138,17 @@ private static String getStackTraceAsString(Exception exception) {
 
         return sb.toString();
     }
+
+    private static String resolveErrorType(Exception exception) {
+        String simpleName = exception.getClass().getSimpleName();
+        if (!simpleName.isEmpty()) {
+            return simpleName;
+        }
+        // 익명 클래스의 경우 simpleName이 빈 문자열이므로 부모 클래스 이름 사용
+        Class<?> superClass = exception.getClass().getSuperclass();
+        if (superClass != null) {
+            return superClass.getSimpleName();
+        }
+        return exception.getClass().getName();
+    }
 }