Merge pull request #47229 from kzittritsch

* pr/47229:
  Polish contribution
  Add configuration property for Tomcat's static resource cache max size

Closes gh-47229

Author: snicoll

module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatServerProperties.java

@@ -694,6 +694,11 @@ public static class Resource {
 		 */
 		private boolean allowCaching = true;
 
+		/**
+		 * Maximum size of the static resource cache.
+		 */
+		private DataSize cacheMaxSize = DataSize.ofMegabytes(10);
+
 		/**
 		 * Time-to-live of the static resource cache.
 		 */
@@ -707,6 +712,14 @@ public void setAllowCaching(boolean allowCaching) {
 			this.allowCaching = allowCaching;
 		}
 
+		public DataSize getCacheMaxSize() {
+			return this.cacheMaxSize;
+		}
+
+		public void setCacheMaxSize(DataSize cacheMaxSize) {
+			this.cacheMaxSize = cacheMaxSize;
+		}
+
 		public @Nullable Duration getCacheTtl() {
 			return this.cacheTtl;
 		}

module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizer.java

@@ -380,6 +380,8 @@ private void customizeStaticResources(ConfigurableTomcatWebServerFactory factory
 		factory.addContextCustomizers((context) -> context.addLifecycleListener((event) -> {
 			if (event.getType().equals(Lifecycle.CONFIGURE_START_EVENT)) {
 				context.getResources().setCachingAllowed(resource.isAllowCaching());
+				long cacheMaxSize = resource.getCacheMaxSize().toKilobytes();
+				context.getResources().setCacheMaxSize(cacheMaxSize);
 				if (resource.getCacheTtl() != null) {
 					long ttl = resource.getCacheTtl().toMillis();
 					context.getResources().setCacheTtl(ttl);

module/spring-boot-tomcat/src/test/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizerTests.java

@@ -322,6 +322,18 @@ void customRemoteIpValve() {
 		assertThat(remoteIpValve.getTrustedProxies()).isEqualTo("proxy1|proxy2");
 	}
 
+	@Test
+	void resourceCacheMatchesDefault() {
+		TomcatServerProperties properties = new TomcatServerProperties();
+		customizeAndRunServer((server) -> {
+			Tomcat tomcat = server.getTomcat();
+			Context context = (Context) tomcat.getHost().findChildren()[0];
+			assertThat(properties.getResource().isAllowCaching()).isEqualTo(context.getResources().isCachingAllowed());
+			assertThat(properties.getResource().getCacheMaxSize())
+				.isEqualTo(DataSize.ofKilobytes(context.getResources().getCacheMaxSize()));
+		});
+	}
+
 	@Test
 	void customStaticResourceAllowCaching() {
 		bind("server.tomcat.resource.allow-caching=false");
@@ -332,6 +344,16 @@ void customStaticResourceAllowCaching() {
 		});
 	}
 
+	@Test
+	void customStaticResourceCacheMaxSize() {
+		bind("server.tomcat.resource.cache-max-size=4MB");
+		customizeAndRunServer((server) -> {
+			Tomcat tomcat = server.getTomcat();
+			Context context = (Context) tomcat.getHost().findChildren()[0];
+			assertThat(context.getResources().getCacheMaxSize()).isEqualTo(4096L);
+		});
+	}
+
 	@Test
 	void customStaticResourceCacheTtl() {
 		bind("server.tomcat.resource.cache-ttl=10000");