feat: 상품 아이템 조회 API 구현

Author: nilgil

src/main/kotlin/com/nilgil/commerce/common/GlobalExceptionHandler.kt

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+package com.nilgil.commerce.common
+
+import jakarta.persistence.EntityNotFoundException
+import org.springframework.http.HttpStatus
+import org.springframework.web.bind.annotation.ControllerAdvice
+import org.springframework.web.bind.annotation.ExceptionHandler
+import org.springframework.web.bind.annotation.ResponseStatus
+
+@ControllerAdvice
+class GlobalExceptionHandler {
+    @ExceptionHandler(EntityNotFoundException::class)
+    @ResponseStatus(HttpStatus.NOT_FOUND)
+    fun handleEntityNotFoundException(ex: EntityNotFoundException) {
+    }
+}

src/main/kotlin/com/nilgil/commerce/product/ProductImageRepository.kt

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+package com.nilgil.commerce.product
+
+import org.springframework.data.jpa.repository.JpaRepository
+
+interface ProductImageRepository : JpaRepository<ProductImage, Long> {
+    fun findByProductAndType(
+        product: Product,
+        type: ProductImageType,
+    ): ProductImage?
+
+    fun findAllByProductInAndType(
+        products: List<Product>,
+        type: ProductImageType,
+    ): List<ProductImage>
+}

src/main/kotlin/com/nilgil/commerce/product/ProductItemController.kt

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+package com.nilgil.commerce.product
+
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.PathVariable
+import org.springframework.web.bind.annotation.RequestParam
+import org.springframework.web.bind.annotation.RestController
+
+@RestController
+class ProductItemController(
+    private val service: ProductItemService,
+) {
+    @GetMapping("/product-items/{id}")
+    fun getProductItem(
+        @PathVariable id: Long,
+    ): ProductItemResponse = service.getProductItem(id)
+
+    @GetMapping("/product-items")
+    fun getProductItems(
+        @RequestParam ids: List<Long>,
+    ): List<ProductItemResponse> = service.getProductItems(ids)
+}

src/main/kotlin/com/nilgil/commerce/product/ProductItemOptionElementRepository.kt

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+package com.nilgil.commerce.product
+
+import org.springframework.data.jpa.repository.EntityGraph
+import org.springframework.data.jpa.repository.JpaRepository
+
+interface ProductItemOptionElementRepository : JpaRepository<ProductItemOptionElement, Long> {
+    @EntityGraph(attributePaths = ["optionElement.option"])
+    fun findAllWithOptionDetailsByItem(item: ProductItem): List<ProductItemOptionElement>
+
+    @EntityGraph(attributePaths = ["optionElement.option"])
+    fun findAllWithOptionDetailsByItemIn(items: List<ProductItem>): List<ProductItemOptionElement>
+}

src/main/kotlin/com/nilgil/commerce/product/ProductItemRepository.kt

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+package com.nilgil.commerce.product
+
+import org.springframework.data.jpa.repository.EntityGraph
+import org.springframework.data.jpa.repository.JpaRepository
+
+interface ProductItemRepository : JpaRepository<ProductItem, Long> {
+    @EntityGraph(attributePaths = ["product"])
+    fun findWithProductById(productItemId: Long): ProductItem?
+
+    @EntityGraph(attributePaths = ["product"])
+    fun findWithProductByIdIn(productItemIds: List<Long>): List<ProductItem>
+}

src/main/kotlin/com/nilgil/commerce/product/ProductItemResponse.kt

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+package com.nilgil.commerce.product
+
+data class ProductItemResponse(
+    val id: Long,
+    val productName: String,
+    val options: Map<String, String>,
+    val thumbnailImageUrl: String?,
+    val price: Int,
+    val stock: Int,
+) {
+    companion object {
+        fun from(
+            productItem: ProductItem,
+            options: Map<String, String>,
+            thumbnailUrl: String?,
+        ): ProductItemResponse =
+            ProductItemResponse(
+                id = productItem.id,
+                productName = productItem.product.name,
+                options = options,
+                thumbnailImageUrl = thumbnailUrl,
+                price = productItem.getAdjustedPrice(),
+                stock = productItem.stock,
+            )
+    }
+}

src/main/kotlin/com/nilgil/commerce/product/ProductItemService.kt

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+package com.nilgil.commerce.product
+
+import jakarta.persistence.EntityNotFoundException
+import org.springframework.stereotype.Service
+
+@Service
+class ProductItemService(
+    private val productItemRepository: ProductItemRepository,
+    private val productImageRepository: ProductImageRepository,
+    private val productItemOptionElementRepository: ProductItemOptionElementRepository,
+) {
+    fun getProductItem(id: Long): ProductItemResponse {
+        val productItem = findProductItemOrThrow(id)
+        val options = findOptionMap(productItem)
+        val thumbnailUrl = findThumbnailUrlOrNull(productItem.product)
+
+        return ProductItemResponse.from(
+            productItem = productItem,
+            options = options,
+            thumbnailUrl = thumbnailUrl,
+        )
+    }
+
+    fun getProductItems(ids: List<Long>): List<ProductItemResponse> {
+        val productItems = productItemRepository.findWithProductByIdIn(ids)
+        if (productItems.isEmpty()) {
+            return emptyList()
+        }
+
+        val thumbnailUrlMap = getProductIdThumbnailUrlMap(productItems)
+        val optionElementsMap = getProductItemIdOptionElementsMap(productItems)
+
+        val responseMap =
+            productItems.associateBy(
+                keySelector = { it.id },
+                valueTransform = { item ->
+                    ProductItemResponse.from(
+                        productItem = item,
+                        options = optionElementsMap[item.id] ?: emptyMap(),
+                        thumbnailUrl = thumbnailUrlMap[item.product.id],
+                    )
+                },
+            )
+
+        return ids.mapNotNull { responseMap[it] }
+    }
+
+    private fun findProductItemOrThrow(id: Long): ProductItem =
+        productItemRepository.findWithProductById(id)
+            ?: throw EntityNotFoundException("상품 아이템을 찾을 수 없습니다. id: $id")
+
+    private fun findOptionMap(item: ProductItem): Map<String, String> =
+        productItemOptionElementRepository
+            .findAllWithOptionDetailsByItem(item)
+            .associate { it.optionElement.option.name to it.optionElement.name }
+
+    private fun findThumbnailUrlOrNull(product: Product): String? =
+        productImageRepository.findByProductAndType(product, ProductImageType.THUMBNAIL)?.url
+
+    private fun getProductIdThumbnailUrlMap(productItems: List<ProductItem>): Map<Long, String> {
+        val products = productItems.map { productItem -> productItem.product }
+        return productImageRepository
+            .findAllByProductInAndType(products, ProductImageType.THUMBNAIL)
+            .associate { it.product.id to it.url }
+    }
+
+    private fun getProductItemIdOptionElementsMap(productItems: List<ProductItem>): Map<Long, Map<String, String>> =
+        productItemOptionElementRepository
+            .findAllWithOptionDetailsByItemIn(productItems)
+            .groupBy { it.item.id }
+            .mapValues { it.value.associate { it -> it.optionElement.option.name to it.optionElement.name } }
+}