Add BodyInserters.fromValue(T, ParameterizedTypeReference<T>)

This commit introduces
BodyInserters.fromValue(T, ParameterizedTypeReference<T>) variant as
well as related WebClient.RequestBodySpec API,
ServerResponse.BodyBuilder API and Kotlin extensions.

Closes gh-32713

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

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.reactive.function
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.springframework.core.ParameterizedTypeReference
+import org.springframework.http.codec.EncoderHttpMessageWriter
+import org.springframework.http.codec.HttpMessageWriter
+import org.springframework.http.codec.json.KotlinSerializationJsonEncoder
+import org.springframework.http.server.reactive.ServerHttpRequest
+import org.springframework.web.testfixture.http.server.reactive.MockServerHttpResponse
+import reactor.test.StepVerifier
+import java.util.*
+
+/**
+ * @author Sebastien Deleuze
+ */
+class KotlinBodyInsertersTests {
+
+	private lateinit var context: BodyInserter.Context
+
+	private lateinit var hints: Map<String, Any>
+
+
+	@BeforeEach
+	fun createContext() {
+		val messageWriters: MutableList<HttpMessageWriter<*>> = ArrayList()
+		val jsonEncoder = KotlinSerializationJsonEncoder()
+		messageWriters.add(EncoderHttpMessageWriter(jsonEncoder))
+
+		this.context = object : BodyInserter.Context {
+			override fun messageWriters(): List<HttpMessageWriter<*>> {
+				return messageWriters
+			}
+
+			override fun serverRequest(): Optional<ServerHttpRequest> {
+				return Optional.empty()
+			}
+
+			override fun hints(): Map<String, Any> {
+				return hints
+			}
+		}
+		this.hints = HashMap()
+	}
+
+	@Test
+	fun ofObjectWithBodyType() {
+		val somebody = SomeBody(1, "name")
+		val body = listOf(somebody)
+		val inserter = BodyInserters.fromValue(body, object: ParameterizedTypeReference<List<SomeBody>>() {})
+		val response = MockServerHttpResponse()
+		val result = inserter.insert(response, context)
+		StepVerifier.create(result).expectComplete().verify()
+
+		StepVerifier.create(response.bodyAsString)
+			.expectNext("[{\"user_id\":1,\"name\":\"name\"}]")
+			.expectComplete()
+			.verify()
+	}
+
+	@Serializable
+	data class SomeBody(@SerialName("user_id") val userId: Int, val name: String)
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -66,6 +66,13 @@ class WebClientExtensionsTests {
 		verify { requestBodySpec.body(ofType<Any>(), object : ParameterizedTypeReference<List<Foo>>() {}) }
 	}
 
+	@Test
+	fun `RequestBodySpec#bodyValueWithType with reified type parameters`() {
+		val body = mockk<List<Foo>>()
+		requestBodySpec.bodyValueWithType<List<Foo>>(body)
+		verify { requestBodySpec.bodyValue(body, object : ParameterizedTypeReference<List<Foo>>() {}) }
+	}
+
 	@Test
 	fun `ResponseSpec#bodyToMono with reified type parameters`() {
 		responseSpec.bodyToMono<List<Foo>>()

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -75,6 +75,19 @@ class ServerResponseExtensionsTests {
 		}
 	}
 
+	@Test
+	fun `BodyBuilder#bodyValueWithTypeAndAwait with object parameter and reified type parameters`() {
+		val response = mockk<ServerResponse>()
+		val body = listOf("foo", "bar")
+		every { bodyBuilder.bodyValue(ofType<List<String>>(), object : ParameterizedTypeReference<List<String>>() {}) } returns Mono.just(response)
+		runBlocking {
+			bodyBuilder.bodyValueWithTypeAndAwait<List<String>>(body)
+		}
+		verify {
+			bodyBuilder.bodyValue(body, object : ParameterizedTypeReference<List<String>>() {})
+		}
+	}
+
 	@Test
 	fun `BodyBuilder#bodyAndAwait with flow parameter`() {
 		val response = mockk<ServerResponse>()