Add hints for web resource default locations

Closes gh-31278

Author: snicoll

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

@@ -0,0 +1,46 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.web;
+
+import java.util.List;
+
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
+
+/**
+ * {@link RuntimeHintsRegistrar} for default locations of web resources.
+ *
+ * @author Stephane Nicoll
+ * @since 3.0
+ */
+public class WebResourcesRuntimeHintsRegistrar implements RuntimeHintsRegistrar {
+
+	private static final List<String> DEFAULT_LOCATIONS = List.of("META-INF/resources/", "resources/", "static/",
+			"public/");
+
+	@Override
+	public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+		ClassLoader classLoaderToUse = (classLoader != null) ? classLoader : getClass().getClassLoader();
+		String[] locations = DEFAULT_LOCATIONS.stream()
+				.filter((candidate) -> classLoaderToUse.getResource(candidate) != null)
+				.map((location) -> location + "*").toArray(String[]::new);
+		if (locations.length > 0) {
+			hints.resources().registerPattern((hint) -> hint.includes(locations));
+		}
+	}
+
+}

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

@@ -39,6 +39,7 @@
 import org.springframework.boot.autoconfigure.web.ServerProperties;
 import org.springframework.boot.autoconfigure.web.WebProperties;
 import org.springframework.boot.autoconfigure.web.WebProperties.Resources;
+import org.springframework.boot.autoconfigure.web.WebResourcesRuntimeHintsRegistrar;
 import org.springframework.boot.autoconfigure.web.format.DateTimeFormatters;
 import org.springframework.boot.autoconfigure.web.format.WebConversionService;
 import org.springframework.boot.autoconfigure.web.reactive.WebFluxProperties.Format;
@@ -50,6 +51,7 @@
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.context.annotation.ImportRuntimeHints;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.format.FormatterRegistry;
@@ -104,6 +106,7 @@
 @ConditionalOnClass(WebFluxConfigurer.class)
 @ConditionalOnMissingBean({ WebFluxConfigurationSupport.class })
 @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
+@ImportRuntimeHints(WebResourcesRuntimeHintsRegistrar.class)
 public class WebFluxAutoConfiguration {
 
 	@Bean

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

@@ -50,6 +50,7 @@
 import org.springframework.boot.autoconfigure.web.WebProperties;
 import org.springframework.boot.autoconfigure.web.WebProperties.Resources;
 import org.springframework.boot.autoconfigure.web.WebProperties.Resources.Chain.Strategy;
+import org.springframework.boot.autoconfigure.web.WebResourcesRuntimeHintsRegistrar;
 import org.springframework.boot.autoconfigure.web.format.DateTimeFormatters;
 import org.springframework.boot.autoconfigure.web.format.WebConversionService;
 import org.springframework.boot.autoconfigure.web.servlet.WebMvcProperties.Format;
@@ -64,6 +65,7 @@
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.context.annotation.ImportRuntimeHints;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.io.Resource;
@@ -143,6 +145,7 @@
 @ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
 @ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
 @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
+@ImportRuntimeHints(WebResourcesRuntimeHintsRegistrar.class)
 public class WebMvcAutoConfiguration {
 
 	/**

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

@@ -0,0 +1,89 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.web;
+
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.List;
+import java.util.function.Consumer;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.hint.ResourcePatternHint;
+import org.springframework.aot.hint.ResourcePatternHints;
+import org.springframework.aot.hint.RuntimeHints;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link WebResourcesRuntimeHintsRegistrar}.
+ *
+ * @author Stephane Nicoll
+ */
+class WebResourcesRuntimeHintsRegistrarTests {
+
+	@Test
+	void registerHintsWithAllLocations() {
+		RuntimeHints hints = register(
+				new TestClassLoader(List.of("META-INF/resources/", "resources/", "static/", "public/")));
+		assertThat(hints.resources().resourcePatterns()).singleElement()
+				.satisfies(include("META-INF/resources/*", "resources/*", "static/*", "public/*"));
+	}
+
+	@Test
+	void registerHintsWithOnlyStaticLocations() {
+		RuntimeHints hints = register(new TestClassLoader(List.of("static/")));
+		assertThat(hints.resources().resourcePatterns()).singleElement().satisfies(include("static/*"));
+	}
+
+	@Test
+	void registerHintsWithNoLocation() {
+		RuntimeHints hints = register(new TestClassLoader(List.of()));
+		assertThat(hints.resources().resourcePatterns()).isEmpty();
+	}
+
+	RuntimeHints register(ClassLoader classLoader) {
+		RuntimeHints hints = new RuntimeHints();
+		WebResourcesRuntimeHintsRegistrar registrar = new WebResourcesRuntimeHintsRegistrar();
+		registrar.registerHints(hints, classLoader);
+		return hints;
+	}
+
+	private Consumer<ResourcePatternHints> include(String... patterns) {
+		return (hint) -> {
+			assertThat(hint.getIncludes()).map(ResourcePatternHint::getPattern).containsExactly(patterns);
+			assertThat(hint.getExcludes()).isEmpty();
+		};
+	}
+
+	private static class TestClassLoader extends URLClassLoader {
+
+		private final List<String> availableResources;
+
+		TestClassLoader(List<String> availableResources) {
+			super(new URL[0], TestClassLoader.class.getClassLoader());
+			this.availableResources = availableResources;
+		}
+
+		@Override
+		public URL getResource(String name) {
+			return (this.availableResources.contains(name)) ? super.getResource("web/custom-resource.txt") : null;
+		}
+
+	}
+
+}