add global exception handler for controllers

add new not found exception, add new test for ShopController

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

@@ -1,11 +1,11 @@
 package com.example.demo.controllers
 
+import com.example.demo.exceptions.NotFoundException
 import com.example.demo.provider.ShopProvider
 import jakarta.servlet.http.HttpServletResponse
 import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.encodeToJsonElement
 import org.springframework.beans.factory.annotation.Autowired
-import org.springframework.http.HttpStatus
 import org.springframework.web.bind.annotation.GetMapping
 import org.springframework.web.bind.annotation.ResponseBody
 import org.springframework.web.bind.annotation.RestController
@@ -16,14 +16,9 @@ class ShopController (
 ) {
     @GetMapping(value = ["/shop/common-info"], produces = ["application/json"])
     @ResponseBody
+    @Throws(NotFoundException::class)
     fun commonInfo(response: HttpServletResponse): String {
-        val shop = shopProvider.getRandomShop()
-
-        if (shop == null) {
-            response.status = HttpStatus.NOT_FOUND.value()
-
-            return "not found"
-        }
+        val shop = shopProvider.getRandomShop() ?: throw NotFoundException()
 
         return Json.encodeToJsonElement(value = mapOf(
             "customers" to mapOf(

src/main/kotlin/com/example/demo/exceptions/ExceptionHandler.kt

@@ -0,0 +1,13 @@
+package com.example.demo.exceptions
+
+import com.example.demo.responses.makeNotFound
+import org.springframework.http.HttpStatus
+import org.springframework.http.ResponseEntity
+import org.springframework.web.bind.annotation.ControllerAdvice
+import org.springframework.web.bind.annotation.ExceptionHandler
+
+@ControllerAdvice
+class ExceptionHandler {
+    @ExceptionHandler(NotFoundException::class)
+    fun handleNotFound(): ResponseEntity<Any> = ResponseEntity(makeNotFound(), HttpStatus.NOT_FOUND)
+}

src/main/kotlin/com/example/demo/exceptions/NotFoundException.kt

@@ -0,0 +1,3 @@
+package com.example.demo.exceptions
+
+class NotFoundException: RuntimeException()

src/main/kotlin/com/example/demo/responses/BaseResponse.kt

@@ -0,0 +1,5 @@
+package com.example.demo.responses
+
+class BaseResponse(val status: ResponseStatus)
+
+fun makeNotFound(): BaseResponse = BaseResponse(status = ResponseStatus.NOT_FOUND)

src/main/kotlin/com/example/demo/responses/ResponseStatus.kt

@@ -0,0 +1,7 @@
+package com.example.demo.responses
+
+import com.fasterxml.jackson.annotation.JsonValue
+
+enum class ResponseStatus(@JsonValue val status: String) {
+    NOT_FOUND("not found");
+}

src/test/kotlin/com/example/demo/controllers/ShopControllerTest.kt

@@ -11,6 +11,8 @@ import org.springframework.test.web.servlet.MockMvc
 import org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get
 import org.springframework.test.web.servlet.result.MockMvcResultMatchers.content
 import org.springframework.test.web.servlet.result.MockMvcResultMatchers.status
+import java.time.OffsetDateTime
+import java.util.*
 import kotlin.test.Test
 
 @WebMvcTest(ShopController::class)
@@ -20,30 +22,35 @@ class ShopControllerTest(@Autowired val mockMvc: MockMvc) {
 
     @Test
     fun commonInfo_shouldSeeSuccessResponseJson() {
+        val productOne = makeProduct(id = 1, name = "one", price = 11.2)
+        val productTwo = makeProduct(id = 2, name = "two", price = 13.2)
+        val productThree = makeProduct(id = 3, name = "three", price = 15.2)
+        val productFour = makeProduct(id = 4, name = "four", price = 14.2)
+
         val shopMock = Shop(name="shop", customers= listOf(
             Customer(
                 name = "cus-one",
                 city = City(name= "city-one"),
                 orders = listOf(
-                    Order(products = listOf(Product(name = "one", price = 11.2)), isDelivered = false),
-                    Order(products = listOf(Product(name = "two", price = 13.2)), isDelivered = false),
-                    Order(products = listOf(Product(name = "three", price = 15.2)), isDelivered = true),
+                    Order(products = listOf(productOne), isDelivered = false),
+                    Order(products = listOf(productTwo), isDelivered = false),
+                    Order(products = listOf(productThree), isDelivered = true),
                 )
             ),
             Customer(
                 name = "cus-two",
                 city = City(name= "city-two"),
                 orders = listOf(
-                    Order(products = listOf(Product(name = "one", price = 12.2)), isDelivered = false),
-                    Order(products = listOf(Product(name = "two", price = 13.2)), isDelivered = true),
-                    Order(products = listOf(Product(name = "four", price = 14.2)), isDelivered = true),
+                    Order(products = listOf(productOne), isDelivered = false),
+                    Order(products = listOf(productTwo), isDelivered = true),
+                    Order(products = listOf(productFour), isDelivered = true),
                 )
             ),
         ))
 
         val expectedJson: String = """{
             |"customers": {"withMoreUndeliveredOrdersThanDelivered": ["cus-one"]},
-            |"products": {"orderedByAllCustomers": ["two"]}
+            |"products": {"orderedByAllCustomers": ["one", "two"]}
             |}""".trimMargin()
 
         whenever(
@@ -55,4 +62,28 @@ class ShopControllerTest(@Autowired val mockMvc: MockMvc) {
             .andExpect(content().contentType("application/json"))
             .andExpect(content().json(expectedJson))
     }
+
+    @Test
+    fun commonInfo_shouldSeeNotFoundResponse() {
+        whenever(
+            shopProvider.getRandomShop()
+        ) doReturn (null)
+
+        mockMvc.perform(get("/shop/common-info"))
+            .andExpect(status().isNotFound)
+            .andExpect(content().contentType("application/json"))
+            .andExpect(content().json("""{"status":"not found"}"""))
+    }
+
+    private fun makeProduct(id: Long, name: String, price: Double): Product {
+        return Product(
+            id = id,
+            guid = UUID.randomUUID(),
+            name = name,
+            description = null,
+            price = (price * 100).toInt(),
+            createdAt = OffsetDateTime.now(),
+            updatedAt = null,
+        )
+    }
 }