Preserve generic type info in awaitEntity()

awaitEntity() used T::class.java which erases generic type
information (e.g. List<Foo> becomes just List). Use the
reified toEntity<T>() extension instead, which preserves
full generic type via ParameterizedTypeReference.

Closes gh-36834
Signed-off-by: wushiyuanmaimob <wushiyuanwork@outlook.com>

Author: wushiyuanmaimob

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/client/WebClientExtensions.kt

@@ -236,7 +236,7 @@ inline fun <reified T : Any> WebClient.ResponseSpec.toEntityFlux(): Mono<Respons
 suspend inline fun <reified T : Any> WebClient.ResponseSpec.awaitEntity(): ResponseEntity<T> {
 	val context = currentCoroutineContext().minusKey(Job.Key)
 	return withContext(context.toReactorContext()) {
-		toEntity(T::class.java).awaitSingle()
+		toEntity<T>().awaitSingle()
 	}
 }
 

spring-webflux/src/test/kotlin/org/springframework/web/reactive/function/client/WebClientExtensionsTests.kt

@@ -219,6 +219,14 @@ class WebClientExtensionsTests {
 		verify { responseSpec.toEntityFlux(object : ParameterizedTypeReference<List<Foo>>() {}) }
 	}
 
+	@Test
+	suspend fun `awaitEntity preserves generic type information`() {
+		val spec = mockk<WebClient.ResponseSpec>()
+		val entity = mockk<ResponseEntity<List<Foo>>>()
+		every { spec.toEntity(any<ParameterizedTypeReference<List<Foo>>>()) } returns Mono.just(entity)
+		assertThat(spec.awaitEntity<List<Foo>>()).isEqualTo(entity)
+	}
+
 	@Test
 	fun `ResponseSpec#awaitEntity with coroutine context propagation`() {
 		val exchangeFunction = mockk<ExchangeFunction>()
@@ -230,7 +238,7 @@ class WebClientExtensionsTests {
 		every { mockResponse.statusCode() } returns HttpStatus.OK
 		every { mockResponse.headers() } returns mockClientHeaders
 		every { mockClientHeaders.asHttpHeaders() } returns HttpHeaders()
-		every { mockResponse.bodyToMono(Foo::class.java) } returns Mono.just(foo)
+		every { mockResponse.bodyToMono(any<ParameterizedTypeReference<Foo>>()) } returns Mono.just(foo)
 		runBlocking(FooContextElement(foo)) {
 			val responseEntity = WebClient.builder()
 				.exchangeFunction(exchangeFunction)
@@ -258,7 +266,7 @@ class WebClientExtensionsTests {
 		every { mockResponse.statusCode() } returns HttpStatus.OK
 		every { mockResponse.headers() } returns mockClientHeaders
 		every { mockClientHeaders.asHttpHeaders() } returns HttpHeaders()
-		every { mockResponse.bodyToMono(Foo::class.java) } returns Mono.just(foo)
+		every { mockResponse.bodyToMono(any<ParameterizedTypeReference<Foo>>()) } returns Mono.just(foo)
 		runBlocking {
 			val responseEntity = WebClient.builder()
 				.exchangeFunction(exchangeFunction)