Add file pattern resource hints registrar

This commit adds a utility method to register resources on the classpath
based on a location, name, and extension.

Closes gh-28626

spring-core/src/main/java/org/springframework/aot/hint/support/FilePatternResourceHintsRegistrar.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright 2002-2022 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.aot.hint.support;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.springframework.aot.hint.ResourceHints;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.ResourceUtils;
+
+/**
+ * Register the necessary resource hints for loading files from the classpath.
+ *
+ * <p>Candidates are identified by a file name, a location, and an extension.
+ * The location can be the empty string to refer to the root of the classpath.
+ *
+ * @author Stephane Nicoll
+ * @since 6.0
+ */
+public class FilePatternResourceHintsRegistrar {
+
+	private final List<String> names;
+
+	private final List<String> locations;
+
+	private final List<String> extensions;
+
+	/**
+	 * Create a new instance for the specified file names, locations, and file
+	 * extensions.
+	 * @param names the file names
+	 * @param locations the classpath locations
+	 * @param extensions the file extensions (starts with a dot)
+	 */
+	public FilePatternResourceHintsRegistrar(List<String> names, List<String> locations,
+			List<String> extensions) {
+		this.names = validateNames(names);
+		this.locations = validateLocations(locations);
+		this.extensions = validateExtensions(extensions);
+	}
+
+	private static List<String> validateNames(List<String> names) {
+		for (String name : names) {
+			if (name.contains("*")) {
+				throw new IllegalArgumentException("File name '" + name + "' cannot contain '*'");
+			}
+		}
+		return names;
+	}
+
+	private static List<String> validateLocations(List<String> locations) {
+		Assert.notEmpty(locations, () -> "At least one location should be specified");
+		List<String> parsedLocations = new ArrayList<>();
+		for (String location : locations) {
+			if (location.startsWith(ResourceUtils.CLASSPATH_URL_PREFIX)) {
+				location = location.substring(ResourceUtils.CLASSPATH_URL_PREFIX.length());
+			}
+			if (location.startsWith("/")) {
+				location = location.substring(1);
+			}
+			if (!location.isEmpty() && !location.endsWith("/")) {
+				location = location + "/";
+			}
+			parsedLocations.add(location);
+		}
+		return parsedLocations;
+
+	}
+
+	private static List<String> validateExtensions(List<String> extensions) {
+		for (String extension : extensions) {
+			if (!extension.startsWith(".")) {
+				throw new IllegalArgumentException("Extension '" + extension + "' should start with '.'");
+			}
+		}
+		return extensions;
+	}
+
+	public void registerHints(ResourceHints hints, @Nullable ClassLoader classLoader) {
+		ClassLoader classLoaderToUse = (classLoader != null) ? classLoader : getClass().getClassLoader();
+		List<String> includes = new ArrayList<>();
+		for (String location : this.locations) {
+			if (classLoaderToUse.getResource(location) != null) {
+				for (String extension : this.extensions) {
+					for (String name : this.names) {
+						includes.add(location + name + "*" + extension);
+					}
+				}
+			}
+		}
+		if (!includes.isEmpty()) {
+			hints.registerPattern(hint -> hint.includes(includes.toArray(String[]::new)));
+		}
+	}
+}

spring-core/src/test/java/org/springframework/aot/hint/support/FilePatternResourceHintsRegistrarTests.java

@@ -0,0 +1,135 @@
+/*
+ * Copyright 2002-2022 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.aot.hint.support;
+
+import java.util.List;
+import java.util.function.Consumer;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.hint.ResourceHints;
+import org.springframework.aot.hint.ResourcePatternHint;
+import org.springframework.aot.hint.ResourcePatternHints;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+
+/**
+ * Tests for {@link FilePatternResourceHintsRegistrar}.
+ *
+ * @author Stephane Nicoll
+ */
+class FilePatternResourceHintsRegistrarTests {
+
+	private final ResourceHints hints = new ResourceHints();
+
+	@Test
+	void createWithInvalidName() {
+		assertThatIllegalArgumentException().isThrownBy(() -> new FilePatternResourceHintsRegistrar(
+						List.of("test*"), List.of(""), List.of(".txt")))
+				.withMessageContaining("cannot contain '*'");
+	}
+
+	@Test
+	void createWithInvalidExtension() {
+		assertThatIllegalArgumentException().isThrownBy(() -> new FilePatternResourceHintsRegistrar(
+						List.of("test"), List.of(""), List.of("txt")))
+				.withMessageContaining("should start with '.'");
+	}
+
+	@Test
+	void registerWithSinglePattern() {
+		new FilePatternResourceHintsRegistrar(List.of("test"), List.of(""), List.of(".txt"))
+				.registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).singleElement()
+				.satisfies(includes("test*.txt"));
+	}
+
+	@Test
+	void registerWithMultipleNames() {
+		new FilePatternResourceHintsRegistrar(List.of("test", "another"), List.of(""), List.of(".txt"))
+				.registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).singleElement()
+				.satisfies(includes("test*.txt", "another*.txt"));
+	}
+
+	@Test
+	void registerWithMultipleLocations() {
+		new FilePatternResourceHintsRegistrar(List.of("test"), List.of("", "META-INF"), List.of(".txt"))
+				.registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).singleElement()
+				.satisfies(includes("test*.txt", "META-INF/test*.txt"));
+	}
+
+	@Test
+	void registerWithMultipleExtensions() {
+		new FilePatternResourceHintsRegistrar(List.of("test"), List.of(""), List.of(".txt", ".conf"))
+				.registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).singleElement()
+				.satisfies(includes("test*.txt", "test*.conf"));
+	}
+
+	@Test
+	void registerWithLocationWithoutTrailingSlash() {
+		new FilePatternResourceHintsRegistrar(List.of("test"), List.of("META-INF"), List.of(".txt"))
+				.registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).singleElement()
+				.satisfies(includes("META-INF/test*.txt"));
+	}
+
+	@Test
+	void registerWithLocationWithLeadingSlash() {
+		new FilePatternResourceHintsRegistrar(List.of("test"), List.of("/"), List.of(".txt"))
+				.registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).singleElement()
+				.satisfies(includes("test*.txt"));
+	}
+
+	@Test
+	void registerWithLocationUsingResourceClasspathPrefix() {
+		new FilePatternResourceHintsRegistrar(List.of("test"), List.of("classpath:META-INF"), List.of(".txt"))
+				.registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).singleElement()
+				.satisfies(includes("META-INF/test*.txt"));
+	}
+
+	@Test
+	void registerWithLocationUsingResourceClasspathPrefixAndTrailingSlash() {
+		new FilePatternResourceHintsRegistrar(List.of("test"), List.of("classpath:/META-INF"), List.of(".txt"))
+				.registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).singleElement()
+				.satisfies(includes("META-INF/test*.txt"));
+	}
+
+	@Test
+	void registerWithNonExistingLocationDoesNotRegisterHint() {
+		new FilePatternResourceHintsRegistrar(List.of("test"),
+				List.of("does-not-exist/", "another-does-not-exist/"),
+				List.of(".txt")).registerHints(this.hints, null);
+		assertThat(this.hints.resourcePatterns()).isEmpty();
+	}
+
+
+	private Consumer<ResourcePatternHints> includes(String... patterns) {
+		return hint -> {
+			assertThat(hint.getIncludes().stream().map(ResourcePatternHint::getPattern))
+					.containsExactlyInAnyOrder(patterns);
+			assertThat(hint.getExcludes()).isEmpty();
+		};
+	}
+
+}