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/main/java/org/springframework/web/reactive/function/BodyInserters.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 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.
@@ -103,6 +103,32 @@ public abstract class BodyInserters {
 				writeWithMessageWriters(message, context, Mono.just(body), ResolvableType.forInstance(body), null);
 	}
 
+	/**
+	 * Inserter to write the given value.
+	 * <p>Alternatively, consider using the {@code bodyValue(Object, ParameterizedTypeReference)} shortcuts on
+	 * {@link org.springframework.web.reactive.function.client.WebClient WebClient} and
+	 * {@link org.springframework.web.reactive.function.server.ServerResponse ServerResponse}.
+	 * @param body the value to write
+	 * @param bodyType the type of the body, used to capture the generic type
+	 * @param <T> the type of the body
+	 * @return the inserter to write a single value
+	 * @throws IllegalArgumentException if {@code body} is a {@link Publisher} or an
+	 * instance of a type supported by {@link ReactiveAdapterRegistry#getSharedInstance()},
+	 * for which {@link #fromPublisher(Publisher, ParameterizedTypeReference)} or
+	 * {@link #fromProducer(Object, ParameterizedTypeReference)} should be used.
+	 * @since 6.2
+	 * @see #fromPublisher(Publisher, ParameterizedTypeReference)
+	 * @see #fromProducer(Object, ParameterizedTypeReference)
+	 */
+	public static <T> BodyInserter<T, ReactiveHttpOutputMessage> fromValue(T body, ParameterizedTypeReference<T> bodyType) {
+		Assert.notNull(body, "'body' must not be null");
+		Assert.notNull(bodyType, "'bodyType' must not be null");
+		Assert.isNull(registry.getAdapter(body.getClass()),
+				"'body' should be an object, for reactive types use a variant specifying a publisher/producer and its related element type");
+		return (message, context) ->
+				writeWithMessageWriters(message, context, Mono.just(body), ResolvableType.forType(bodyType), null);
+	}
+
 	/**
 	 * Inserter to write the given object.
 	 * <p>Alternatively, consider using the {@code bodyValue(Object)} shortcuts on

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java

@@ -367,6 +367,12 @@ final class DefaultWebClient implements WebClient {
 			return this;
 		}
 
+		@Override
+		public <T> RequestHeadersSpec<?> bodyValue(T body, ParameterizedTypeReference<T> bodyType) {
+			this.inserter = BodyInserters.fromValue(body, bodyType);
+			return this;
+		}
+
 		@Override
 		public <T, P extends Publisher<T>> RequestHeadersSpec<?> body(
 				P publisher, ParameterizedTypeReference<T> elementTypeRef) {

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClient.java

@@ -692,9 +692,38 @@ public interface WebClient {
 		 * @throws IllegalArgumentException if {@code body} is a
 		 * {@link Publisher} or producer known to {@link ReactiveAdapterRegistry}
 		 * @since 5.2
+		 * @see #bodyValue(Object, ParameterizedTypeReference)
 		 */
 		RequestHeadersSpec<?> bodyValue(Object body);
 
+		/**
+		 * Shortcut for {@link #body(BodyInserter)} with a
+		 * {@linkplain BodyInserters#fromValue value inserter}.
+		 * For example:
+		 * <p><pre class="code">
+		 * List&lt;Person&gt; list = ... ;
+		 *
+		 * Mono&lt;Void&gt; result = client.post()
+		 *     .uri("/persons/{id}", id)
+		 *     .contentType(MediaType.APPLICATION_JSON)
+		 *     .bodyValue(list, new ParameterizedTypeReference&lt;List&lt;Person&gt;&gt;() {};)
+		 *     .retrieve()
+		 *     .bodyToMono(Void.class);
+		 * </pre>
+		 * <p>For multipart requests consider providing
+		 * {@link org.springframework.util.MultiValueMap MultiValueMap} prepared
+		 * with {@link org.springframework.http.client.MultipartBodyBuilder
+		 * MultipartBodyBuilder}.
+		 * @param body the value to write to the request body
+		 * @param bodyType the type of the body, used to capture the generic type
+		 * @param <T> the type of the body
+		 * @return this builder
+		 * @throws IllegalArgumentException if {@code body} is a
+		 * {@link Publisher} or producer known to {@link ReactiveAdapterRegistry}
+		 * @since 6.2
+		 */
+		<T> RequestHeadersSpec<?> bodyValue(T body, ParameterizedTypeReference<T> bodyType);
+
 		/**
 		 * Shortcut for {@link #body(BodyInserter)} with a
 		 * {@linkplain BodyInserters#fromPublisher Publisher inserter}.

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerResponseBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 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.
@@ -225,6 +225,11 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 		return initBuilder(body, BodyInserters.fromValue(body));
 	}
 
+	@Override
+	public <T> Mono<ServerResponse> bodyValue(T body, ParameterizedTypeReference<T> bodyType) {
+		return initBuilder(body, BodyInserters.fromValue(body, bodyType));
+	}
+
 	@Override
 	public <T, P extends Publisher<T>> Mono<ServerResponse> body(P publisher, Class<T> elementClass) {
 		return initBuilder(publisher, BodyInserters.fromPublisher(publisher, elementClass));

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/ServerResponse.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 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.
@@ -420,6 +420,20 @@ public interface ServerResponse {
 		 */
 		Mono<ServerResponse> bodyValue(Object body);
 
+		/**
+		 * Set the body of the response to the given {@code Object} and return it.
+		 * This is a shortcut for using a {@link #body(BodyInserter)} with a
+		 * {@linkplain BodyInserters#fromValue value inserter}.
+		 * @param body the body of the response
+		 * @param bodyType the type of the body, used to capture the generic type
+		 * @param <T> the type of the body
+		 * @return the built response
+		 * @throws IllegalArgumentException if {@code body} is a
+		 * {@link Publisher} or producer known to {@link ReactiveAdapterRegistry}
+		 * @since 6.2
+		 */
+		<T> Mono<ServerResponse> bodyValue(T body, ParameterizedTypeReference<T> bodyType);
+
 		/**
 		 * Set the body from the given {@code Publisher}. Shortcut for
 		 * {@link #body(BodyInserter)} with a

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 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.
@@ -68,6 +68,18 @@ inline fun <reified T : Any> RequestBodySpec.body(flow: Flow<T>): RequestHeaders
 inline fun <reified T : Any> RequestBodySpec.body(producer: Any): RequestHeadersSpec<*> =
 		body(producer, object : ParameterizedTypeReference<T>() {})
 
+/**
+ * Extension for [WebClient.RequestBodySpec.bodyValue] providing a `bodyValueWithType<T>(Any)` variant
+ * leveraging Kotlin reified type parameters. This extension is not subject to type
+ * erasure and retains actual generic type arguments.
+ * @param body the value to write to the request body
+ * @param T the type of the body
+ * @author Sebastien Deleuze
+ * @since 6.2
+ */
+inline fun <reified T : Any> RequestBodySpec.bodyValueWithType(body: T): RequestHeadersSpec<*> =
+	bodyValue(body, object : ParameterizedTypeReference<T>() {})
+
 /**
  * Coroutines variant of [WebClient.RequestHeadersSpec.exchange].
  *

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

@@ -51,9 +51,6 @@ inline fun <reified T : Any> ServerResponse.BodyBuilder.body(producer: Any): Mon
 /**
  * Coroutines variant of [ServerResponse.BodyBuilder.bodyValue].
  *
- * Set the body of the response to the given {@code Object} and return it.
- * This convenience method combines [body] and
- * [org.springframework.web.reactive.function.BodyInserters.fromValue].
  * @param body the body of the response
  * @return the built response
  * @throws IllegalArgumentException if `body` is a [Publisher] or an
@@ -62,6 +59,21 @@ inline fun <reified T : Any> ServerResponse.BodyBuilder.body(producer: Any): Mon
 suspend fun ServerResponse.BodyBuilder.bodyValueAndAwait(body: Any): ServerResponse =
 		bodyValue(body).awaitSingle()
 
+/**
+ * Coroutines variant of [ServerResponse.BodyBuilder.bodyValue] providing a `bodyValueWithTypeAndAwait<T>(Any)` variant
+ * leveraging Kotlin reified type parameters. This extension is not subject to type
+ * erasure and retains actual generic type arguments.
+ *
+ * @param body the body of the response
+ * @param T the type of the body
+ * @return the built response
+ * @throws IllegalArgumentException if `body` is a [Publisher] or an
+ * instance of a type supported by [org.springframework.core.ReactiveAdapterRegistry.getSharedInstance],
+ * @since 6.2
+ */
+suspend inline fun <reified T: Any> ServerResponse.BodyBuilder.bodyValueWithTypeAndAwait(body: T): ServerResponse =
+	bodyValue(body, object : ParameterizedTypeReference<T>() {}).awaitSingle()
+
 /**
  * Coroutines variant of [ServerResponse.BodyBuilder.body] with [Any] and
  * [ParameterizedTypeReference] parameters providing a `bodyAndAwait(Flow<T>)` variant.

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>()