add product repository, controller, tests

src/main/kotlin/com/example/demo/AppConfig.kt

@@ -4,8 +4,10 @@ import com.example.demo.provider.MockedShopProvider
 import com.example.demo.provider.ShopProvider
 import org.springframework.context.annotation.Bean
 import org.springframework.context.annotation.Configuration
+import org.springframework.data.jpa.repository.config.EnableJpaRepositories
 
 @Configuration
+@EnableJpaRepositories(basePackages = ["com.example.demo.providers"])
 class AppConfig {
     @Bean
     fun shopProvider(): ShopProvider{

src/main/kotlin/com/example/demo/controllers/ProductController.kt

@@ -0,0 +1,25 @@
+package com.example.demo.controllers
+
+import com.example.demo.exceptions.NotFoundException
+import com.example.demo.provider.ProductRepository
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.encodeToJsonElement
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.web.bind.annotation.*
+import java.util.*
+
+@RestController
+@RequestMapping(value = ["/api/product"])
+class ProductController(
+    @Autowired val productRepository: ProductRepository
+) {
+    @GetMapping(value = ["{guid}"], produces = ["application/json"])
+    @ResponseBody
+    fun getProduct(
+        @PathVariable guid: UUID
+    ): String {
+        val product = productRepository.findByGuid(guid = guid) ?: throw NotFoundException()
+
+        return Json.encodeToJsonElement(value = product).toString()
+    }
+}

src/main/kotlin/com/example/demo/provider/ProductRepository.kt

@@ -0,0 +1,13 @@
+package com.example.demo.provider
+
+import com.example.demo.models.Product
+import org.springframework.data.jpa.repository.Query
+import org.springframework.data.repository.CrudRepository
+import org.springframework.stereotype.Repository
+import java.util.*
+
+@Repository
+interface ProductRepository: CrudRepository<Product, Long> {
+    @Query(value = "SELECT * FROM Product WHERE guid = :guid")
+    fun findByGuid(guid: UUID): Product?
+}