Merge pull request #31709 from aooohan

* gh-31709:
  Polish "Add auto-configuration for JdkClientHttpConnector"
  Add auto-configuration for JdkClientHttpConnector

Closes gh-31709

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/function/client/ClientHttpConnectorAutoConfiguration.java

@@ -41,7 +41,7 @@ import org.springframework.web.reactive.function.client.WebClient;
 @AutoConfiguration
 @ConditionalOnClass(WebClient.class)
 @Import({ ClientHttpConnectorConfiguration.ReactorNetty.class, ClientHttpConnectorConfiguration.JettyClient.class,
-		ClientHttpConnectorConfiguration.HttpClient5.class })
+		ClientHttpConnectorConfiguration.HttpClient5.class, ClientHttpConnectorConfiguration.JdkClient.class })
 public class ClientHttpConnectorAutoConfiguration {
 
 	@Bean

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/function/client/ClientHttpConnectorConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -31,6 +31,7 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Lazy;
 import org.springframework.http.client.reactive.ClientHttpConnector;
 import org.springframework.http.client.reactive.HttpComponentsClientHttpConnector;
+import org.springframework.http.client.reactive.JdkClientHttpConnector;
 import org.springframework.http.client.reactive.JettyClientHttpConnector;
 import org.springframework.http.client.reactive.JettyResourceFactory;
 import org.springframework.http.client.reactive.ReactorClientHttpConnector;
@@ -107,4 +108,17 @@ class ClientHttpConnectorConfiguration {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(java.net.http.HttpClient.class)
+	@ConditionalOnMissingBean(ClientHttpConnector.class)
+	static class JdkClient {
+
+		@Bean
+		@Lazy
+		JdkClientHttpConnector jdkClientHttpConnector() {
+			return new JdkClientHttpConnector();
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/function/client/ClientHttpConnectorAutoConfigurationTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.autoconfigure.web.reactive.function.client;
 
+import org.apache.hc.client5.http.impl.async.HttpAsyncClients;
 import org.eclipse.jetty.reactive.client.ReactiveRequest;
 import org.junit.jupiter.api.Test;
 import reactor.netty.http.client.HttpClient;
@@ -85,6 +86,21 @@ class ClientHttpConnectorAutoConfigurationTests {
 				});
 	}
 
+	@Test
+	void whenReactorJettyAndHttpClientBeansAreUnavailableThenJdkClientBeansAreDefined() {
+		this.contextRunner
+				.withClassLoader(
+						new FilteredClassLoader(HttpClient.class, ReactiveRequest.class, HttpAsyncClients.class))
+				.run((context) -> {
+					BeanDefinition customizerDefinition = context.getBeanFactory()
+							.getBeanDefinition("clientConnectorCustomizer");
+					assertThat(customizerDefinition.isLazyInit()).isTrue();
+					BeanDefinition connectorDefinition = context.getBeanFactory()
+							.getBeanDefinition("jdkClientHttpConnector");
+					assertThat(connectorDefinition.isLazyInit()).isTrue();
+				});
+	}
+
 	@Test
 	void shouldCreateHttpClientBeans() {
 		this.contextRunner.run((context) -> {

spring-boot-project/spring-boot-docs/src/docs/asciidoc/io/rest-client.adoc

@@ -63,7 +63,7 @@ include::code:MyService[]
 [[io.rest-client.webclient.runtime]]
 ==== WebClient Runtime
 Spring Boot will auto-detect which `ClientHttpConnector` to use to drive `WebClient`, depending on the libraries available on the application classpath.
-For now, Reactor Netty, Jetty RS client and Apache HttpClient are supported.
+For now, Reactor Netty, Jetty RS client, Apache HttpClient, and the JDK's HttpClient are supported.
 
 The `spring-boot-starter-webflux` starter depends on `io.projectreactor.netty:reactor-netty` by default, which brings both server and client implementations.
 If you choose to use Jetty as a reactive server instead, you should add a dependency on the Jetty Reactive HTTP client library, `org.eclipse.jetty:jetty-reactive-httpclient`.