Configure Undertow not to presever path on forward by default

Closes gh-23619

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

@@ -1548,6 +1548,11 @@ public class ServerProperties {
 		 */
 		private Duration noRequestTimeout;
 
+		/**
+		 * Whether to preserve the path of a request when it is forwarded.
+		 */
+		private boolean preservePathOnForward = false;
+
 		private final Accesslog accesslog = new Accesslog();
 
 		/**
@@ -1675,6 +1680,14 @@ public class ServerProperties {
 			this.noRequestTimeout = noRequestTimeout;
 		}
 
+		public boolean isPreservePathOnForward() {
+			return this.preservePathOnForward;
+		}
+
+		public void setPreservePathOnForward(boolean preservePathOnForward) {
+			this.preservePathOnForward = preservePathOnForward;
+		}
+
 		public Accesslog getAccesslog() {
 			return this.accesslog;
 		}

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

@@ -39,6 +39,7 @@ public class UndertowServletWebServerFactoryCustomizer
 	@Override
 	public void customize(UndertowServletWebServerFactory factory) {
 		factory.setEagerInitFilters(this.serverProperties.getUndertow().isEagerFilterInit());
+		factory.setPreservePathOnForward(this.serverProperties.getUndertow().isPreservePathOnForward());
 	}
 
 }

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

@@ -40,4 +40,14 @@ class UndertowServletWebServerFactoryCustomizerTests {
 		assertThat(factory.isEagerInitFilters()).isFalse();
 	}
 
+	@Test
+	void preservePathOnForwardCanBeEnabled() {
+		UndertowServletWebServerFactory factory = new UndertowServletWebServerFactory(0);
+		assertThat(factory.isPreservePathOnForward()).isFalse();
+		ServerProperties serverProperties = new ServerProperties();
+		serverProperties.getUndertow().setPreservePathOnForward(true);
+		new UndertowServletWebServerFactoryCustomizer(serverProperties).customize(factory);
+		assertThat(factory.isPreservePathOnForward()).isTrue();
+	}
+
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java

@@ -93,6 +93,8 @@ public class UndertowServletWebServerFactory extends AbstractServletWebServerFac
 
 	private boolean eagerInitFilters = true;
 
+	private boolean preservePathOnForward = false;
+
 	/**
 	 * Create a new {@link UndertowServletWebServerFactory} instance.
 	 */
@@ -261,6 +263,26 @@ public class UndertowServletWebServerFactory extends AbstractServletWebServerFac
 		this.eagerInitFilters = eagerInitFilters;
 	}
 
+	/**
+	 * Return where the request path should be preserved on forward.
+	 * @return {@code true} if the path should be preserved when a request is forwarded,
+	 * otherwise {@code false}.
+	 * @since 2.4.0
+	 */
+	public boolean isPreservePathOnForward() {
+		return this.preservePathOnForward;
+	}
+
+	/**
+	 * Set whether the request path should be preserved on forward.
+	 * @param preservePathOnForward {@code true} if the path should be preserved when a
+	 * request is forwarded, otherwise {@code false}.
+	 * @since 2.4.0
+	 */
+	public void setPreservePathOnForward(boolean preservePathOnForward) {
+		this.preservePathOnForward = preservePathOnForward;
+	}
+
 	@Override
 	public WebServer getWebServer(ServletContextInitializer... initializers) {
 		Builder builder = this.delegate.createBuilder(this);
@@ -283,6 +305,7 @@ public class UndertowServletWebServerFactory extends AbstractServletWebServerFac
 		deployment.setResourceManager(getDocumentRootResourceManager());
 		deployment.setTempDir(createTempDir("undertow"));
 		deployment.setEagerFilterInit(this.eagerInitFilters);
+		deployment.setPreservePathOnForward(this.preservePathOnForward);
 		configureMimeMappings(deployment);
 		for (UndertowDeploymentInfoCustomizer customizer : this.deploymentInfoCustomizers) {
 			customizer.customize(deployment);