refactor: PaymentService 로직 수정 및 \@Transactional 명시

- 읽고 null이 아니면 필드 조회 -> 필드를 쿼리로 바로 조회
- 단순한 존재 여부 판단 -> find => exists로 수정

src/main/java/roomescape/payment/business/PaymentService.kt

@@ -15,15 +15,12 @@ import roomescape.payment.web.ReservationPaymentResponse
 import roomescape.payment.web.toReservationPaymentResponse
 import roomescape.reservation.domain.Reservation
 import java.time.OffsetDateTime
-import java.util.*
-import java.util.function.Supplier
 
 @Service
 class PaymentService(
         private val paymentRepository: PaymentRepository,
         private val canceledPaymentRepository: CanceledPaymentRepository
 ) {
-
     @Transactional
     fun savePayment(
             paymentResponse: PaymentApprove.Response,
@@ -39,46 +36,73 @@ class PaymentService(
     }.toReservationPaymentResponse()
 
     @Transactional(readOnly = true)
-    fun findPaymentByReservationId(reservationId: Long): Optional<PaymentEntity> {
+    fun isReservationPaid(
-        return paymentRepository.findByReservationId(reservationId)
+            reservationId: Long
-    }
+    ): Boolean = paymentRepository.existsByReservationId(reservationId)
 
-    fun saveCanceledPayment(cancelInfo: PaymentCancel.Response, approvedAt: OffsetDateTime, paymentKey: String) {
+    @Transactional
-        canceledPaymentRepository.save<CanceledPaymentEntity?>(CanceledPaymentEntity(null,
+    fun saveCanceledPayment(
-                paymentKey, cancelInfo.cancelReason, cancelInfo.cancelAmount, approvedAt, cancelInfo.canceledAt))
+            cancelInfo: PaymentCancel.Response,
-    }
+            approvedAt: OffsetDateTime,
+            paymentKey: String
+    ): CanceledPaymentEntity = CanceledPaymentEntity(
+            paymentKey = paymentKey,
+            cancelReason = cancelInfo.cancelReason,
+            cancelAmount = cancelInfo.cancelAmount,
+            approvedAt = approvedAt,
+            canceledAt = cancelInfo.canceledAt
+    ).also { canceledPaymentRepository.save(it) }
 
+
+    @Transactional
     fun cancelPaymentByAdmin(reservationId: Long): PaymentCancel.Request {
-        val paymentKey = findPaymentByReservationId(reservationId)
+        val paymentKey: String = paymentRepository.findPaymentKeyByReservationId(reservationId)
-                .orElseThrow<RoomescapeException?>(java.util.function.Supplier {
+                ?: throw RoomescapeException(
-                    RoomescapeException(roomescape.common.exception.ErrorType.PAYMENT_NOT_POUND,
+                        ErrorType.PAYMENT_NOT_POUND,
-                            kotlin.String.format("[reservationId: %d]", reservationId), org.springframework.http.HttpStatus.NOT_FOUND)
+                        "[reservationId: $reservationId]",
-                })!!
+                        HttpStatus.NOT_FOUND
-                .paymentKey
+                )
         // 취소 시간은 현재 시간으로 일단 생성한 뒤, 결제 취소 완료 후 해당 시간으로 변경합니다.
-        val canceled = cancelPayment(paymentKey, "고객 요청", OffsetDateTime.now())
+        val canceled: CanceledPaymentEntity = cancelPayment(paymentKey)
 
         return PaymentCancel.Request(paymentKey, canceled.cancelAmount, canceled.cancelReason)
     }
 
-    private fun cancelPayment(paymentKey: String, cancelReason: String, canceledAt: OffsetDateTime): CanceledPaymentEntity {
+    private fun cancelPayment(
-        val paymentEntity = paymentRepository.findByPaymentKey(paymentKey)
+            paymentKey: String,
-                .orElseThrow<RoomescapeException?>(Supplier { throwPaymentNotFoundByPaymentKey(paymentKey) })
+            cancelReason: String = "고객 요청",
-        paymentRepository.delete(paymentEntity)
+            canceledAt: OffsetDateTime = OffsetDateTime.now()
+    ): CanceledPaymentEntity {
+        val paymentEntity: PaymentEntity = paymentRepository.findByPaymentKey(paymentKey)
+                ?.also { paymentRepository.delete(it) }
+                ?: throw RoomescapeException(
+                        ErrorType.PAYMENT_NOT_POUND,
+                        "[paymentKey: $paymentKey]",
+                        HttpStatus.NOT_FOUND
+                )
 
-        return canceledPaymentRepository.save<CanceledPaymentEntity>(CanceledPaymentEntity(null, paymentKey, cancelReason, paymentEntity.totalAmount,
+        return CanceledPaymentEntity(
-                paymentEntity.approvedAt, canceledAt))
+                paymentKey = paymentKey,
+                cancelReason = cancelReason,
+                cancelAmount = paymentEntity.totalAmount,
+                approvedAt = paymentEntity.approvedAt,
+                canceledAt = canceledAt
+        ).also {
+            canceledPaymentRepository.save(it)
+        }
     }
 
-    fun updateCanceledTime(paymentKey: String, canceledAt: OffsetDateTime) {
+    @Transactional
-        val canceledPayment = canceledPaymentRepository.findByPaymentKey(paymentKey)
+    fun updateCanceledTime(
-                .orElseThrow<RoomescapeException?>(Supplier { throwPaymentNotFoundByPaymentKey(paymentKey) })
+            paymentKey: String,
-        canceledPayment.canceledAt = canceledAt
+            canceledAt: OffsetDateTime
-    }
+    ) {
-
+        canceledPaymentRepository.findByPaymentKey(paymentKey)?.let {
-    private fun throwPaymentNotFoundByPaymentKey(paymentKey: String?): RoomescapeException {
+            it.canceledAt = canceledAt
-        return RoomescapeException(
+        } ?: throw RoomescapeException(
-                ErrorType.PAYMENT_NOT_POUND, String.format("[paymentKey: %s]", paymentKey),
+                ErrorType.PAYMENT_NOT_POUND,
-                HttpStatus.NOT_FOUND)
+                "[paymentKey: $paymentKey]",
+                HttpStatus.NOT_FOUND
+        )
     }
 }

src/main/java/roomescape/reservation/service/ReservationWithPaymentService.java

@@ -47,7 +47,7 @@ public class ReservationWithPaymentService {
 
 	@Transactional(readOnly = true)
 	public boolean isNotPaidReservation(Long reservationId) {
-		return paymentService.findPaymentByReservationId(reservationId).isEmpty();
+		return !paymentService.isReservationPaid(reservationId);
 	}
 
 	public void updateCanceledTime(String paymentKey, OffsetDateTime canceledAt) {