Compatibility with HtmlUnit 2.51

Includes upgrade to Tomcat 9.0.50, Jetty 9.4.43, Jackson 2.12.4.

Closes gh-27147

build.gradle

@@ -27,12 +27,12 @@ configure(allprojects) { project ->
 
 	dependencyManagement {
 		imports {
-			mavenBom "com.fasterxml.jackson:jackson-bom:2.12.3"
+			mavenBom "com.fasterxml.jackson:jackson-bom:2.12.4"
 			mavenBom "io.netty:netty-bom:4.1.65.Final"
 			mavenBom "io.projectreactor:reactor-bom:2020.0.8"
 			mavenBom "io.r2dbc:r2dbc-bom:Arabba-SR10"
 			mavenBom "io.rsocket:rsocket-bom:1.1.1"
-			mavenBom "org.eclipse.jetty:jetty-bom:9.4.42.v20210604"
+			mavenBom "org.eclipse.jetty:jetty-bom:9.4.43.v20210629"
 			mavenBom "org.jetbrains.kotlin:kotlin-bom:1.5.10"
 			mavenBom "org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.5.0"
 			mavenBom "org.jetbrains.kotlinx:kotlinx-serialization-bom:1.2.1"
@@ -127,14 +127,14 @@ configure(allprojects) { project ->
 			dependency "org.webjars:webjars-locator-core:0.47"
 			dependency "org.webjars:underscorejs:1.8.3"
 
-			dependencySet(group: 'org.apache.tomcat', version: '9.0.48') {
+			dependencySet(group: 'org.apache.tomcat', version: '9.0.50') {
 				entry 'tomcat-util'
 				entry('tomcat-websocket') {
 					exclude group: "org.apache.tomcat", name: "tomcat-websocket-api"
 					exclude group: "org.apache.tomcat", name: "tomcat-servlet-api"
 				}
 			}
-			dependencySet(group: 'org.apache.tomcat.embed', version: '9.0.48') {
+			dependencySet(group: 'org.apache.tomcat.embed', version: '9.0.50') {
 				entry 'tomcat-embed-core'
 				entry 'tomcat-embed-websocket'
 			}
@@ -204,10 +204,10 @@ configure(allprojects) { project ->
 			}
 			dependency "io.mockk:mockk:1.11.0"
 
-			dependency("net.sourceforge.htmlunit:htmlunit:2.50.0") {
+			dependency("net.sourceforge.htmlunit:htmlunit:2.51.0") {
 				exclude group: "commons-logging", name: "commons-logging"
 			}
-			dependency("org.seleniumhq.selenium:htmlunit-driver:2.50.0") {
+			dependency("org.seleniumhq.selenium:htmlunit-driver:2.51.0") {
 				exclude group: "commons-logging", name: "commons-logging"
 			}
 			dependency("org.seleniumhq.selenium:selenium-java:3.141.59") {

spring-test/src/main/java/org/springframework/test/web/servlet/htmlunit/webdriver/WebConnectionHtmlUnitDriver.java

 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -22,7 +22,6 @@ import com.gargoylesoftware.htmlunit.WebConnection;
 import org.openqa.selenium.Capabilities;
 import org.openqa.selenium.htmlunit.HtmlUnitDriver;
 
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -35,15 +34,12 @@ import org.springframework.util.Assert;
  *
  * @author Rob Winch
  * @author Sam Brannen
+ * @author Juergen Hoeller
  * @since 4.2
  * @see MockMvcHtmlUnitDriverBuilder
  */
 public class WebConnectionHtmlUnitDriver extends HtmlUnitDriver {
 
-	@Nullable
-	private WebClient webClient;
-
-
 	public WebConnectionHtmlUnitDriver() {
 	}
 
@@ -72,9 +68,7 @@ public class WebConnectionHtmlUnitDriver extends HtmlUnitDriver {
 	 */
 	@Override
 	protected final WebClient modifyWebClient(WebClient webClient) {
-		this.webClient = super.modifyWebClient(webClient);
-		this.webClient = modifyWebClientInternal(this.webClient);
-		return this.webClient;
+		return modifyWebClientInternal(super.modifyWebClient(webClient));
 	}
 
 	/**
@@ -90,13 +84,12 @@ public class WebConnectionHtmlUnitDriver extends HtmlUnitDriver {
 	}
 
 	/**
-	 * Return the current {@link WebClient}.
+	 * Return the current {@link WebClient} in a public fashion.
 	 * @since 4.3
 	 */
 	@Override
 	public WebClient getWebClient() {
-		Assert.state(this.webClient != null, "No WebClient set");
-		return this.webClient;
+		return super.getWebClient();
 	}
 
 	/**