Add hints for web resource default locations

Closes gh-31278

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;
+		}
+
+	}
+
+}