Refine WebFlux Coroutines API

This commit provides both nullable and non-nullable variants for
awaitBody, makes awaitPrincipal return type nullable and rename
awaitResponse to awaitExchange for better consistency with Java API.

See gh-19975

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

@@ -16,6 +16,7 @@
 
 package org.springframework.web.reactive.function.client
 
+import kotlinx.coroutines.reactive.awaitFirstOrNull
 import kotlinx.coroutines.reactive.awaitSingle
 import org.springframework.core.ParameterizedTypeReference
 import org.springframework.http.ResponseEntity
@@ -67,7 +68,7 @@ inline fun <reified T : Any> ClientResponse.toEntityList(): Mono<ResponseEntity<
 		toEntityList(object : ParameterizedTypeReference<T>() {})
 
 /**
- * Coroutines variant of [ClientResponse.bodyToMono].
+ * Non-nullable Coroutines variant of [ClientResponse.bodyToMono].
  *
  * @author Sebastien Deleuze
  * @since 5.2
@@ -75,6 +76,15 @@ inline fun <reified T : Any> ClientResponse.toEntityList(): Mono<ResponseEntity<
 suspend inline fun <reified T : Any> ClientResponse.awaitBody(): T =
 		bodyToMono<T>().awaitSingle()
 
+/**
+ * Nullable coroutines variant of [ClientResponse.bodyToMono].
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2
+ */
+suspend inline fun <reified T : Any> ClientResponse.awaitBodyOrNull(): T? =
+		bodyToMono<T>().awaitFirstOrNull()
+
 /**
  * Coroutines variant of [ClientResponse.toEntity].
  *

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

@@ -67,7 +67,7 @@ inline fun <reified T : Any> WebClient.ResponseSpec.bodyToFlux(): Flux<T> =
  * @author Sebastien Deleuze
  * @since 5.2
  */
-suspend fun WebClient.RequestHeadersSpec<out WebClient.RequestHeadersSpec<*>>.awaitResponse(): ClientResponse =
+suspend fun WebClient.RequestHeadersSpec<out WebClient.RequestHeadersSpec<*>>.awaitExchange(): ClientResponse =
 		exchange().awaitSingle()
 
 /**

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/ServerRequestExtensions.kt

@@ -49,12 +49,21 @@ inline fun <reified T : Any> ServerRequest.bodyToFlux(): Flux<T> =
 		bodyToFlux(object : ParameterizedTypeReference<T>() {})
 
 /**
- * Coroutines variant of [ServerRequest.bodyToMono].
+ * Non-nullable Coroutines variant of [ServerRequest.bodyToMono].
  *
  * @author Sebastien Deleuze
  * @since 5.2
  */
-suspend inline fun <reified T : Any> ServerRequest.awaitBody(): T? =
+suspend inline fun <reified T : Any> ServerRequest.awaitBody(): T =
+		bodyToMono<T>().awaitSingle()
+
+/**
+ * Nullable Coroutines variant of [ServerRequest.bodyToMono].
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2
+ */
+suspend inline fun <reified T : Any> ServerRequest.awaitBodyOrNull(): T? =
 		bodyToMono<T>().awaitFirstOrNull()
 
 /**
@@ -81,8 +90,8 @@ suspend fun ServerRequest.awaitMultipartData(): MultiValueMap<String, Part> =
  * @author Sebastien Deleuze
  * @since 5.2
  */
-suspend fun ServerRequest.awaitPrincipal(): Principal =
-		principal().awaitSingle()
+suspend fun ServerRequest.awaitPrincipal(): Principal? =
+		principal().awaitFirstOrNull()
 
 /**
  * Coroutines variant of [ServerRequest.session].

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

@@ -21,6 +21,7 @@ import io.mockk.mockk
 import io.mockk.verify
 import kotlinx.coroutines.runBlocking
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
 import org.junit.Test
 import org.springframework.core.ParameterizedTypeReference
 import org.springframework.http.HttpStatus
@@ -69,6 +70,15 @@ class ClientResponseExtensionsTests {
 		}
 	}
 
+	@Test
+	fun awaitBodyOrNull() {
+		val response = mockk<ClientResponse>()
+		every { response.bodyToMono<String>() } returns Mono.empty()
+		runBlocking {
+			assertNull(response.awaitBodyOrNull<String>())
+		}
+	}
+
 	@Test
 	fun awaitEntity() {
 		val response = mockk<ClientResponse>()

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

@@ -58,11 +58,11 @@ class WebClientExtensionsTests {
 	}
 
 	@Test
-	fun awaitResponse() {
+	fun awaitExchange() {
 		val response = mockk<ClientResponse>()
 		every { requestBodySpec.exchange() } returns Mono.just(response)
 		runBlocking {
-			assertEquals(response, requestBodySpec.awaitResponse())
+			assertEquals(response, requestBodySpec.awaitExchange())
 		}
 	}
 

spring-webflux/src/test/kotlin/org/springframework/web/reactive/function/server/ServerRequestExtensionsTests.kt

@@ -61,10 +61,10 @@ class ServerRequestExtensionsTests {
 	}
 
 	@Test
-	fun awaitBodyNull() {
+	fun awaitBodyOrNull() {
 		every { request.bodyToMono<String>() } returns Mono.empty()
 		runBlocking {
-			assertNull(request.awaitBody<String>())
+			assertNull(request.awaitBodyOrNull<String>())
 		}
 	}