feat: Optimistic Lock 구현

src/main/java/com/kt/common/exception/ErrorCode.java

@@ -50,6 +50,8 @@ public enum ErrorCode {
 	CANNOT_REFUND_ORDER(HttpStatus.BAD_REQUEST, "주문 환불이 불가능합니다."),
 	CANNOT_RETURN_ORDER(HttpStatus.BAD_REQUEST, "주문 반품이 불가능합니다."),
 	CANNOT_UPDATE_ORDER_STATUS(HttpStatus.BAD_REQUEST, "주문 상태 변경이 불가능합니다."),
+	CONCURRENT_RESERVATION(HttpStatus.CONFLICT, "다시 시도해주세요"),
+
 
 	//shoppingaddress
 	NOT_SHOPPING_ADDRESS_OWNER(HttpStatus.FORBIDDEN, "본인의 배송지만 수정/삭제할 수 있습니다."),

src/main/java/com/kt/controller/payment/PaymentController.java

@@ -134,8 +134,6 @@ public ResponseEntity<?> confirmPayment(@RequestBody PaymentTossConfirmRequest r
 					return ResponseEntity.ok(responseBody);
 
 				} catch (Exception e) {
-					System.out.println("결제 실패sdlkjfnmalskdmfklamsdklfmaklsdmfklamsdflkmasdklf");
-
 					cancelTossPayment(paymentKey, "시스템 오류로 인한 자동 취소");
 
 					orderService.rollback(orderIdLong);
@@ -242,7 +240,7 @@ public ApiResult<Map<String, String>> getClientKey() {
 		return ApiResult.ok(Map.of("clientKey", tossPaymentsProperties.getClientKey()));
 	}
 
-	/* 이 코드 service로 빼야하는지 등 검토좀 한번 ㅂ부탁드릴게요!*/
+
 	private void cancelTossPayment(String paymentKey, String cancelReason) {
 		String url = tossPaymentsProperties.getApiUrl() + "/" + paymentKey + "/cancel";
 		String auth = tossPaymentsProperties.getSecretKey() + ":";

src/main/java/com/kt/domain/product/Product.java

@@ -14,6 +14,7 @@
 import jakarta.persistence.JoinColumn;
 import jakarta.persistence.ManyToOne;
 import jakarta.persistence.OneToMany;
+import jakarta.persistence.Version;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 
@@ -34,6 +35,9 @@ public class Product extends BaseEntity {
 
 	private boolean deleted;
 
+	@Version
+	private Long version;
+
 	@ManyToOne
 	@JoinColumn(name = "category_id")
 	private Category category;

src/main/java/com/kt/service/order/OrderService.java

@@ -8,6 +8,7 @@
 import java.util.Objects;
 
 import org.springframework.data.domain.Page;
+import org.springframework.orm.ObjectOptimisticLockingFailureException;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Propagation;
 import org.springframework.transaction.annotation.Transactional;
@@ -124,10 +125,16 @@ public void save(Long orderId){
 		var order = orderRepository.findByIdOrThrow(orderId, ErrorCode.NOT_FOUND_ORDER);
 
 		// stock 차감
-		order.getOrderProducts().forEach(newProduct -> {
+		for (OrderProduct newProduct : order.getOrderProducts()) {
 			var product = newProduct.getProduct();
-			product.updateStock(product.getStock() - newProduct.getCount());
-		});
+
+			try {
+				product.updateStock(product.getStock() - newProduct.getCount());
+				productRepository.saveAndFlush(product); // 버전 체크
+			} catch (ObjectOptimisticLockingFailureException e) {
+				throw new CustomException(ErrorCode.CONCURRENT_RESERVATION);
+			}
+		}
 
 		order.updateStatus(OrderStatus.PAID);
 	}