Configure ForwardedHeaderFilter with Tomcat's use relative redirects

Previously, when Tomcat was configured to use relative redirects
and the ForwardedHeaderFilter is in use, the filter would ignore
the use of the relative redirects.

This commit corrects this misalignment by applying Tomcat's use
relative redirects setting to the filter, but only when Tomcat is
being used as the servlet container.

See gh-29333

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 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.
@@ -85,17 +85,35 @@ public class ServletWebServerFactoryAutoConfiguration {
 		return new TomcatServletWebServerFactoryCustomizer(serverProperties);
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnProperty(value = "server.forward-headers-strategy", havingValue = "framework")
+	static class ForwardedHeaderFilterConfiguration {
+
 		@Bean
+		@ConditionalOnClass(name = "org.apache.catalina.startup.Tomcat")
 		@ConditionalOnMissingFilterBean(ForwardedHeaderFilter.class)
-	@ConditionalOnProperty(value = "server.forward-headers-strategy", havingValue = "framework")
-	public FilterRegistrationBean<ForwardedHeaderFilter> forwardedHeaderFilter() {
+		public FilterRegistrationBean<ForwardedHeaderFilter> tomcatForwardedHeaderFilter(
+				ServerProperties serverProperties) {
+			return createForwardedHeaderFilter(serverProperties.getTomcat().isUseRelativeRedirects());
+		}
+
+		@Bean
+		@ConditionalOnMissingFilterBean(ForwardedHeaderFilter.class)
+		public FilterRegistrationBean<ForwardedHeaderFilter> defaultForwardedHeaderFilter() {
+			return createForwardedHeaderFilter(false);
+		}
+
+		private FilterRegistrationBean<ForwardedHeaderFilter> createForwardedHeaderFilter(boolean relativeRedirects) {
 			ForwardedHeaderFilter filter = new ForwardedHeaderFilter();
+			filter.setRelativeRedirects(relativeRedirects);
 			FilterRegistrationBean<ForwardedHeaderFilter> registration = new FilterRegistrationBean<>(filter);
 			registration.setDispatcherTypes(DispatcherType.REQUEST, DispatcherType.ASYNC, DispatcherType.ERROR);
 			registration.setOrder(Ordered.HIGHEST_PRECEDENCE);
 			return registration;
 		}
 
+	}
+
 	/**
 	 * Registers a {@link WebServerFactoryCustomizerBeanPostProcessor}. Registered via
 	 * {@link ImportBeanDefinitionRegistrar} for early registration.

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

@@ -57,6 +57,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.stereotype.Component;
+import org.springframework.test.util.ReflectionTestUtils;
 import org.springframework.web.filter.ForwardedHeaderFilter;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.FrameworkServlet;
@@ -368,6 +369,36 @@ class ServletWebServerFactoryAutoConfigurationTests {
 				.run((context) -> assertThat(context).hasSingleBean(FilterRegistrationBean.class));
 	}
 
+	@Test
+	void relativeRedirectsShouldBeEnabledWhenUsingTomcatContainerAndUseRelativeRedirects() {
+		WebApplicationContextRunner runner = new WebApplicationContextRunner(
+				AnnotationConfigServletWebServerApplicationContext::new)
+						.withConfiguration(AutoConfigurations.of(ServletWebServerFactoryAutoConfiguration.class))
+						.withPropertyValues("server.forward-headers-strategy=framework",
+								"server.tomcat.use-relative-redirects=true");
+
+		runner.run((context) -> {
+			Filter filter = context.getBean(FilterRegistrationBean.class).getFilter();
+			Boolean relativeRedirects = (Boolean) ReflectionTestUtils.getField(filter, "relativeRedirects");
+			assertThat(relativeRedirects).isTrue();
+		});
+	}
+
+	@Test
+	void relativeRedirectsShouldNotBeEnabledWhenNotUsingTomcatContainer() {
+		WebApplicationContextRunner runner = new WebApplicationContextRunner(
+				AnnotationConfigServletWebServerApplicationContext::new)
+						.withClassLoader(new FilteredClassLoader(Tomcat.class))
+						.withConfiguration(AutoConfigurations.of(ServletWebServerFactoryAutoConfiguration.class))
+						.withPropertyValues("server.forward-headers-strategy=framework");
+
+		runner.run((context) -> {
+			Filter filter = context.getBean(FilterRegistrationBean.class).getFilter();
+			Boolean relativeRedirects = (Boolean) ReflectionTestUtils.getField(filter, "relativeRedirects");
+			assertThat(relativeRedirects).isFalse();
+		});
+	}
+
 	private ContextConsumer<AssertableWebApplicationContext> verifyContext() {
 		return this::verifyContext;
 	}