Stop registering the default servlet by default

Previously, the default servlet was registered automatically when using
embedded Jetty, Tomcat, or Undertow. However, it is not used by the
majority of applications where Spring MVC's DispatcherServlet will be
the only servlet that's needed. As such configuring the default servlet
was wasting CPU and memory.

This commit changes the default for registering the default servlet to
false. It can be re-enabled by setting
server.servlet.register-default-servlet=true.

Closes gh-22915

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

@@ -235,7 +235,7 @@ public class ServerProperties {
 		/**
 		 * Whether to register the default Servlet with the container.
 		 */
-		private boolean registerDefaultServlet = true;
+		private boolean registerDefaultServlet = false;
 
 		@NestedConfigurationProperty
 		private final Encoding encoding = new Encoding();

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jersey/JerseyAutoConfigurationCustomFilterContextPathTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * 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.
@@ -50,8 +50,8 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Dave Syer
  */
-@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT,
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT, properties = { "spring.jersey.type=filter",
-		properties = { "spring.jersey.type=filter", "server.servlet.context-path=/app" })
+		"server.servlet.context-path=/app", "server.servlet.register-default-servlet=true" })
 @DirtiesContext
 class JerseyAutoConfigurationCustomFilterContextPathTests {
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jersey/JerseyAutoConfigurationCustomFilterPathTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * 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.
@@ -50,7 +50,8 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Dave Syer
  */
-@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT, properties = "spring.jersey.type=filter")
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT,
+		properties = { "spring.jersey.type=filter", "server.servlet.register-default-servlet=true" })
 @DirtiesContext
 class JerseyAutoConfigurationCustomFilterPathTests {
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jersey/JerseyAutoConfigurationDefaultFilterPathTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * 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.
@@ -49,7 +49,8 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Dave Syer
  */
-@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT, properties = "spring.jersey.type=filter")
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT,
+		properties = { "spring.jersey.type=filter", "server.servlet.register-default-servlet=true" })
 @DirtiesContext
 class JerseyAutoConfigurationDefaultFilterPathTests {
 

spring-boot-project/spring-boot-devtools/src/test/java/org/springframework/boot/devtools/remote/client/RemoteClientConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * 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.
@@ -156,7 +156,9 @@ class RemoteClientConfigurationTests {
 
 		@Bean
 		TomcatServletWebServerFactory tomcat() {
-			return new TomcatServletWebServerFactory(0);
+			TomcatServletWebServerFactory webServerFactory = new TomcatServletWebServerFactory(0);
+			webServerFactory.setRegisterDefaultServlet(true);
+			return webServerFactory;
 		}
 
 		@Bean

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * 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.
@@ -65,7 +65,7 @@ public abstract class AbstractServletWebServerFactory extends AbstractConfigurab
 
 	private Session session = new Session();
 
-	private boolean registerDefaultServlet = true;
+	private boolean registerDefaultServlet = false;
 
 	private MimeMappings mimeMappings = new MimeMappings(MimeMappings.DEFAULT);
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * 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.
@@ -66,8 +66,8 @@ public interface ConfigurableServletWebServerFactory extends ConfigurableWebServ
 	void setSession(Session session);
 
 	/**
-	 * Set if the DefaultServlet should be registered. Defaults to {@code true} so that
+	 * Set if the DefaultServlet should be registered. Defaults to {@code false} since
-	 * files from the {@link #setDocumentRoot(File) document root} will be served.
+	 * 2.4.
 	 * @param registerDefaultServlet if the default servlet should be registered
 	 */
 	void setRegisterDefaultServlet(boolean registerDefaultServlet);

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactoryTests.java

@@ -378,6 +378,7 @@ public abstract class AbstractServletWebServerFactoryTests {
 	void mimeType() throws Exception {
 		FileCopyUtils.copy("test", new FileWriter(new File(this.tempDir, "test.xxcss")));
 		AbstractServletWebServerFactory factory = getFactory();
+		factory.setRegisterDefaultServlet(true);
 		factory.setDocumentRoot(this.tempDir);
 		MimeMappings mimeMappings = new MimeMappings();
 		mimeMappings.add("xxcss", "text/css");
@@ -544,6 +545,7 @@ public abstract class AbstractServletWebServerFactoryTests {
 	@Test
 	void sslNeedsClientAuthenticationSucceedsWithClientCertificate() throws Exception {
 		AbstractServletWebServerFactory factory = getFactory();
+		factory.setRegisterDefaultServlet(true);
 		addTestTxtFile(factory);
 		factory.setSsl(getSsl(ClientAuth.NEED, "password", "classpath:test.jks", "classpath:test.jks", null, null));
 		this.webServer = factory.getWebServer();
@@ -1200,6 +1202,7 @@ public abstract class AbstractServletWebServerFactoryTests {
 	private void addTestTxtFile(AbstractServletWebServerFactory factory) throws IOException {
 		FileCopyUtils.copy("test", new FileWriter(new File(this.tempDir, "test.txt")));
 		factory.setDocumentRoot(this.tempDir);
+		factory.setRegisterDefaultServlet(true);
 	}
 
 	protected String getLocalUrl(String resourcePath) {

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-traditional/src/main/resources/application.properties

@@ -0,0 +1 @@
+server.servlet.register-default-servlet=true