feat: ticket-order 1대1 비즈니스로직 무결성 보장 로직 추가

* feat: ticket-order 1대1 비즈니스로직 무결성 보장 로직 추가

* chore:

Author: gksdud1109

backend/src/main/java/com/back/api/payment/order/service/OrderService.java

@@ -1,5 +1,6 @@
 package com.back.api.payment.order.service;
 
+import java.util.Optional;
 import java.util.Random;
 import java.util.UUID;
 
@@ -18,9 +19,11 @@
 import com.back.global.error.exception.ErrorException;
 
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 
 @Service
 @RequiredArgsConstructor
+@Slf4j
 public class OrderService {
 	private final OrderRepository orderRepository;
 	private final TicketService ticketService;
@@ -35,6 +38,19 @@ public OrderResponseDto createOrder(OrderRequestDto orderRequestDto, Long userId
 		// 티켓이 DRAFT 상태인지 확인
 		Ticket draft = ticketService.getDraftTicket(orderRequestDto.eventId(), orderRequestDto.seatId(), userId);
 
+		// 이미 PENDING 상태의 Order가 있는지 확인
+		// 다중 요청 방어 로직
+		Optional<Order> existingOrder = orderRepository.findByTicketIdAndStatus(
+			draft.getId(),
+			OrderStatus.PENDING
+		);
+
+		if (existingOrder.isPresent()) {
+			// 기존 Order 재사용 (새로 만들지 않음)
+			log.info("Duplicate order request, reusing existing orderId={}", existingOrder.get().getId());
+			return OrderResponseDto.from(existingOrder.get(), draft);
+		}
+
 		// 금액 일치 여부 확인
 		Integer actualAmount = draft.getSeat().getPrice();
 		if (!orderRequestDto.amount().equals(actualAmount.longValue())) {

backend/src/main/java/com/back/domain/payment/order/repository/OrderRepository.java

@@ -8,6 +8,7 @@
 import org.springframework.stereotype.Repository;
 
 import com.back.domain.payment.order.entity.Order;
+import com.back.domain.payment.order.entity.OrderStatus;
 
 @Repository
 public interface OrderRepository extends JpaRepository<Order, Long> {
@@ -20,4 +21,6 @@ public interface OrderRepository extends JpaRepository<Order, Long> {
 		WHERE o.id = :orderId
 		""")
 	Optional<Order> findByIdWithDetails(@Param("orderId") Long orderId);
+
+	Optional<Order> findByTicketIdAndStatus(Long ticketId, OrderStatus orderStatus);
 }