Add env-based configuration of TTL of Tomcat's static resource cache

Closes gh-9670

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

@@ -609,6 +609,11 @@ public class ServerProperties {
 		 */
 		private List<String> additionalTldSkipPatterns = new ArrayList<>();
 
+		/**
+		 * Static resource configuration.
+		 */
+		private final Resource resource = new Resource();
+
 		public int getMaxThreads() {
 			return this.maxThreads;
 		}
@@ -741,6 +746,10 @@ public class ServerProperties {
 			this.additionalTldSkipPatterns = additionalTldSkipPatterns;
 		}
 
+		public Resource getResource() {
+			return this.resource;
+		}
+
 		/**
 		 * Tomcat access log properties.
 		 */
@@ -880,6 +889,26 @@ public class ServerProperties {
 
 		}
 
+		/**
+		 * Tomcat static resource properties.
+		 */
+		public static class Resource {
+
+			/**
+			 * Time-to-live in milliseconds of the static resource cache.
+			 */
+			private Long cacheTtl;
+
+			public Long getCacheTtl() {
+				return this.cacheTtl;
+			}
+
+			public void setCacheTtl(Long cacheTtl) {
+				this.cacheTtl = cacheTtl;
+			}
+
+		}
+
 	}
 
 	/**

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

@@ -24,6 +24,7 @@ import javax.servlet.ServletException;
 import javax.servlet.SessionCookieConfig;
 
 import io.undertow.UndertowOptions;
+import org.apache.catalina.Lifecycle;
 import org.apache.catalina.valves.AccessLogValve;
 import org.apache.catalina.valves.RemoteIpValve;
 import org.apache.coyote.AbstractProtocol;
@@ -41,6 +42,7 @@ import org.eclipse.jetty.server.handler.HandlerWrapper;
 
 import org.springframework.boot.autoconfigure.web.ServerProperties;
 import org.springframework.boot.autoconfigure.web.ServerProperties.Session;
+import org.springframework.boot.autoconfigure.web.ServerProperties.Tomcat.Resource;
 import org.springframework.boot.cloud.CloudPlatform;
 import org.springframework.boot.web.embedded.jetty.JettyServerCustomizer;
 import org.springframework.boot.web.embedded.jetty.JettyServletWebServerFactory;
@@ -259,6 +261,7 @@ public class DefaultServletWebServerFactoryCustomizer
 				factory.getTldSkipPatterns()
 						.addAll(tomcatProperties.getAdditionalTldSkipPatterns());
 			}
+			customizeStaticResources(serverProperties.getTomcat().getResource(), factory);
 		}
 
 		private static void customizeAcceptCount(TomcatServletWebServerFactory factory,
@@ -384,6 +387,20 @@ public class DefaultServletWebServerFactoryCustomizer
 					.setMapperContextRootRedirectEnabled(redirectContextRoot));
 		}
 
+		private static void customizeStaticResources(Resource resource,
+				TomcatServletWebServerFactory factory) {
+			if (resource.getCacheTtl() == null) {
+				return;
+			}
+			factory.addContextCustomizers((context) -> {
+				context.addLifecycleListener((event) -> {
+					if (event.getType().equals(Lifecycle.CONFIGURE_START_EVENT)) {
+						context.getResources().setCacheTtl(resource.getCacheTtl());
+					}
+				});
+			});
+		}
+
 	}
 
 	private static class UndertowCustomizer {

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

@@ -31,6 +31,7 @@ import javax.servlet.SessionTrackingMode;
 
 import org.apache.catalina.Context;
 import org.apache.catalina.Valve;
+import org.apache.catalina.startup.Tomcat;
 import org.apache.catalina.valves.AccessLogValve;
 import org.apache.catalina.valves.RemoteIpValve;
 import org.apache.coyote.AbstractProtocol;
@@ -602,6 +603,25 @@ public class DefaultServletWebServerFactoryCustomizerTests {
 		verify(factory, never()).setAccessLogEnabled(anyBoolean());
 	}
 
+	@Test
+	public void customTomcatStaticResourceCacheTtl() {
+		Map<String, String> map = new HashMap<>();
+		map.put("server.tomcat.resource.cache-ttl", "10000");
+		bindProperties(map);
+		TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory(0);
+		this.customizer.customize(factory);
+		TomcatWebServer embeddedFactory = (TomcatWebServer) factory.getWebServer();
+		embeddedFactory.start();
+		try {
+			Tomcat tomcat = embeddedFactory.getTomcat();
+			Context context = (Context) tomcat.getHost().findChildren()[0];
+			assertThat(context.getResources().getCacheTtl()).isEqualTo(10000L);
+		}
+		finally {
+			embeddedFactory.stop();
+		}
+	}
+
 	private void triggerInitializers(ConfigurableServletWebServerFactory factory,
 			ServletContext servletContext) throws ServletException {
 		verify(factory, atLeastOnce()).addInitializers(this.initializersCaptor.capture());

spring-boot-project/spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -243,6 +243,7 @@ content into your application; rather pick only the properties that you need.
 	server.tomcat.protocol-header-https-value=https # Value of the protocol header that indicates that the incoming request uses SSL.
 	server.tomcat.redirect-context-root= # Whether requests to the context root should be redirected by appending a / to the path.
 	server.tomcat.remote-ip-header= # Name of the http header from which the remote ip is extracted. For instance `X-FORWARDED-FOR`
+	spring.tomcat.resource.cache-ttl=5000 # Time-to-live in milliseconds of the static resource cache.
 	server.tomcat.uri-encoding=UTF-8 # Character encoding to use to decode the URI.
 	server.undertow.accesslog.dir= # Undertow access log directory.
 	server.undertow.accesslog.enabled=false # Enable access log.