Add bodyNotNull for RestClient Kotlin extensions

Author: Donghh0221

Diff for: spring-web/src/main/kotlin/org/springframework/web/client/RestClientExtensions.kt

@@ -42,6 +42,12 @@ inline fun <reified T : Any> RestClient.RequestBodySpec.bodyWithType(body: T): R
 inline fun <reified T : Any> RestClient.ResponseSpec.body(): T? =
 	body(object : ParameterizedTypeReference<T>() {})
 
+/**
+ * Extension for [RestClient.ResponseSpec.body] providing a `bodyNotNull<Foo>()` variant
+ * To leverage Kotlin null safety, this extension throws a [NoSuchElementException] if the response body is null.
+ */
+inline fun <reified T : Any> RestClient.ResponseSpec.bodyNotNull(): T =
+    body(object : ParameterizedTypeReference<T>() {}) ?: throw NoSuchElementException("Response body is null when a non-null type was expected.")
 
 /**
  * Extension for [RestClient.ResponseSpec.toEntity] providing a `toEntity<Foo>()` variant
@@ -52,4 +58,4 @@ inline fun <reified T : Any> RestClient.ResponseSpec.body(): T? =
  * @since 6.1
  */
 inline fun <reified T : Any> RestClient.ResponseSpec.toEntity(): ResponseEntity<T> =
-	toEntity(object : ParameterizedTypeReference<T>() {})
+	toEntity(object : ParameterizedTypeReference<T>() {})

Diff for: spring-web/src/test/kotlin/org/springframework/web/client/RestClientExtensionsTests.kt

@@ -16,9 +16,11 @@
 
 package org.springframework.web.client
 
+import io.mockk.every
 import io.mockk.mockk
 import io.mockk.verify
 import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
 import org.springframework.core.ParameterizedTypeReference
 
 /**
@@ -45,6 +47,18 @@ class RestClientExtensionsTests {
 		verify { responseSpec.body(object : ParameterizedTypeReference<List<Foo>>() {}) }
 	}
 
+	@Test
+	fun `ResponseSpec#bodyNotNull with reified type parameters`() {
+		responseSpec.bodyNotNull<List<Foo>>()
+		verify { responseSpec.body(object : ParameterizedTypeReference<List<Foo>>() {}) }
+	}
+
+	@Test
+	fun `ResponseSpec#bodyNotNull with null response throws NoSuchElementException`() {
+		every { responseSpec.body(any<ParameterizedTypeReference<Foo>>()) } returns null
+		assertThrows<NoSuchElementException> { responseSpec.bodyNotNull<Foo>() }
+	}
+
 	@Test
 	fun `ResponseSpec#toEntity with reified type parameters`() {
 		responseSpec.toEntity<List<Foo>>()