Harmonize default for server.tomcat.use-relative-redirects

Prior to this commit, the property was a Boolean with a null default.
If it was explicitly set by the user, a context customizer would use
that value to set it on the context. However, if it was not set, the default
wouldn't be tomcat's default but `false` because it was explicitly set to
`false` in `TomcatServletWebServerFactory`. This commit defaults the property
itself to `false` so that the default is more obvious to the user.

Fixes gh-20796

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

@@ -380,7 +380,7 @@ public static class Tomcat {
 		 * Whether HTTP 1.1 and later location headers generated by a call to sendRedirect
 		 * will use relative or absolute redirects.
 		 */
-		private Boolean useRelativeRedirects;
+		private boolean useRelativeRedirects;
 
 		/**
 		 * Character encoding to use to decode the URI.
@@ -537,14 +537,19 @@ public void setRedirectContextRoot(Boolean redirectContextRoot) {
 			this.redirectContextRoot = redirectContextRoot;
 		}
 
-		public Boolean getUseRelativeRedirects() {
+		public boolean getUseRelativeRedirects() {
 			return this.useRelativeRedirects;
 		}
 
-		public void setUseRelativeRedirects(Boolean useRelativeRedirects) {
+		public void setUseRelativeRedirects(boolean useRelativeRedirects) {
 			this.useRelativeRedirects = useRelativeRedirects;
 		}
 
+		@Deprecated
+		public void setUseRelativeRedirects(Boolean useRelativeRedirects) {
+			this.useRelativeRedirects = (useRelativeRedirects != null) ? useRelativeRedirects : false;
+		}
+
 		public String getRemoteIpHeader() {
 			return this.remoteIpHeader;
 		}

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

@@ -54,9 +54,7 @@ public void customize(TomcatServletWebServerFactory factory) {
 		if (tomcatProperties.getRedirectContextRoot() != null) {
 			customizeRedirectContextRoot(factory, tomcatProperties.getRedirectContextRoot());
 		}
-		if (tomcatProperties.getUseRelativeRedirects() != null) {
-			customizeUseRelativeRedirects(factory, tomcatProperties.getUseRelativeRedirects());
-		}
+		customizeUseRelativeRedirects(factory, tomcatProperties.getUseRelativeRedirects());
 		factory.setDisableMBeanRegistry(!tomcatProperties.getMbeanregistry().isEnabled());
 	}
 

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

@@ -131,6 +131,7 @@ void testTomcatBinding() {
 		map.put("server.tomcat.background-processor-delay", "10");
 		map.put("server.tomcat.relaxed-path-chars", "|,<");
 		map.put("server.tomcat.relaxed-query-chars", "^  ,  | ");
+		map.put("server.tomcat.use-relative-redirects", "true");
 		bind(map);
 		ServerProperties.Tomcat tomcat = this.properties.getTomcat();
 		Accesslog accesslog = tomcat.getAccesslog();
@@ -152,6 +153,7 @@ void testTomcatBinding() {
 		assertThat(tomcat.getBackgroundProcessorDelay()).isEqualTo(Duration.ofSeconds(10));
 		assertThat(tomcat.getRelaxedPathChars()).containsExactly('|', '<');
 		assertThat(tomcat.getRelaxedQueryChars()).containsExactly('^', '|');
+		assertThat(tomcat.getUseRelativeRedirects()).isTrue();
 	}
 
 	@Test
@@ -347,6 +349,11 @@ void tomcatInternalProxiesMatchesDefault() {
 				.isEqualTo(new RemoteIpValve().getInternalProxies());
 	}
 
+	@Test
+	void tomcatUseRelativeRedirectsDefaultsToFalse() {
+		assertThat(this.properties.getTomcat().getUseRelativeRedirects()).isFalse();
+	}
+
 	@Test
 	void jettyMaxHttpFormPostSizeMatchesDefault() throws Exception {
 		JettyServletWebServerFactory jettyFactory = new JettyServletWebServerFactory(0);

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactory.java

@@ -214,7 +214,6 @@ protected void prepareContext(Host host, ServletContextInitializer[] initializer
 				: ClassUtils.getDefaultClassLoader());
 		resetDefaultLocaleMapping(context);
 		addLocaleMappings(context);
-		context.setUseRelativeRedirects(false);
 		try {
 			context.setCreateUploadTargets(true);
 		}