Rename property for registering default Servlet

As a follow-up for gh-21214, this commit renames the property to:

`"server.servlet.register-default-servlet=false"`

Closes gh-21214

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

@@ -38,7 +38,6 @@ import org.springframework.boot.web.server.Compression;
 import org.springframework.boot.web.server.Http2;
 import org.springframework.boot.web.server.Shutdown;
 import org.springframework.boot.web.server.Ssl;
-import org.springframework.boot.web.servlet.server.DefaultServlet;
 import org.springframework.boot.web.servlet.server.Encoding;
 import org.springframework.boot.web.servlet.server.Jsp;
 import org.springframework.boot.web.servlet.server.Session;
@@ -227,8 +226,10 @@ public class ServerProperties {
 		 */
 		private String applicationDisplayName = "application";
 
-		@NestedConfigurationProperty
-		private final DefaultServlet defaultServlet = new DefaultServlet();
+		/**
+		 * Whether to register the default Servlet with the container.
+		 */
+		private boolean registerDefaultServlet = true;
 
 		@NestedConfigurationProperty
 		private final Encoding encoding = new Encoding();
@@ -263,12 +264,16 @@ public class ServerProperties {
 			this.applicationDisplayName = displayName;
 		}
 
-		public Map<String, String> getContextParameters() {
-			return this.contextParameters;
+		public boolean isRegisterDefaultServlet() {
+			return this.registerDefaultServlet;
 		}
 
-		public DefaultServlet getDefaultServlet() {
-			return this.defaultServlet;
+		public void setRegisterDefaultServlet(boolean registerDefaultServlet) {
+			this.registerDefaultServlet = registerDefaultServlet;
+		}
+
+		public Map<String, String> getContextParameters() {
+			return this.contextParameters;
 		}
 
 		public Encoding getEncoding() {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/ServletWebServerFactoryCustomizer.java

@@ -53,8 +53,7 @@ public class ServletWebServerFactoryCustomizer
 		map.from(this.serverProperties::getAddress).to(factory::setAddress);
 		map.from(this.serverProperties.getServlet()::getContextPath).to(factory::setContextPath);
 		map.from(this.serverProperties.getServlet()::getApplicationDisplayName).to(factory::setDisplayName);
-		map.from(this.serverProperties.getServlet().getDefaultServlet()::isRegistered)
-				.to(factory::setRegisterDefaultServlet);
+		map.from(this.serverProperties.getServlet()::isRegisterDefaultServlet).to(factory::setRegisterDefaultServlet);
 		map.from(this.serverProperties.getServlet()::getSession).to(factory::setSession);
 		map.from(this.serverProperties::getSsl).to(factory::setSsl);
 		map.from(this.serverProperties.getServlet()::getJsp).to(factory::setJsp);

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/ServletWebServerFactoryCustomizerTests.java

@@ -77,9 +77,9 @@ class ServletWebServerFactoryCustomizerTests {
 	@Test
 	void testCustomizeDefaultServlet() {
 		ConfigurableServletWebServerFactory factory = mock(ConfigurableServletWebServerFactory.class);
-		this.properties.getServlet().getDefaultServlet().setRegistered(true);
+		this.properties.getServlet().setRegisterDefaultServlet(false);
 		this.customizer.customize(factory);
-		verify(factory).setRegisterDefaultServlet(true);
+		verify(factory).setRegisterDefaultServlet(false);
 	}
 
 	@Test

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/server/DefaultServlet.java

@@ -1,40 +0,0 @@
-/*
- * Copyright 2012-2020 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.boot.web.servlet.server;
-
-/**
- * Default Servlet properties.
- *
- * @author Brian Clozel
- * @since 2.3.0
- */
-public class DefaultServlet {
-
-	/**
-	 * Whether to enable the registration of the default Servlet with the container.
-	 */
-	private boolean registered = true;
-
-	public boolean isRegistered() {
-		return this.registered;
-	}
-
-	public void setRegistered(boolean registered) {
-		this.registered = registered;
-	}
-
-}