Fix `PathMatchingResourcePatternResolver` manifest classpath discovery

Update `PathMatchingResourcePatternResolver` so that in addition to
searching the `java.class.path` system property for classpath enties,
it also searches the `MANIFEST.MF` files from within those jars.

Prior to this commit, the `addClassPathManifestEntries()` method
expected that the JVM had added `Class-Path` manifest entries to the
`java.class.path` system property, however, this did not always happen.

The updated code now performs a deep search by loading `MANIFEST.MF`
files from jars discovered from the system property. To deal with
potential performance issue, loaded results are also now cached.

The updated code has been tested with Spring Boot 3.3 jars extracted
using `java -Djarmode=tools`.

See gh-33705

spring-core/src/main/java/org/springframework/core/io/support/PathMatchingResourcePatternResolver.java

@@ -39,16 +39,21 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Collections;
 import java.util.Enumeration;
+import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.NavigableSet;
 import java.util.Objects;
 import java.util.Set;
+import java.util.StringTokenizer;
 import java.util.TreeSet;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Predicate;
+import java.util.jar.Attributes;
+import java.util.jar.Attributes.Name;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
+import java.util.jar.Manifest;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import java.util.zip.ZipException;
@@ -230,6 +235,9 @@ public class PathMatchingResourcePatternResolver implements ResourcePatternResol
 	private static final Predicate<ResolvedModule> isNotSystemModule =
 			resolvedModule -> !systemModuleNames.contains(resolvedModule.name());
 
+	@Nullable
+	private static Set<ClassPathManifestEntry> classPathManifestEntriesCache;
+
 	@Nullable
 	private static Method equinoxResolveMethod;
 
@@ -522,25 +530,30 @@ public class PathMatchingResourcePatternResolver implements ResourcePatternResol
 	 * @since 4.3
 	 */
 	protected void addClassPathManifestEntries(Set<Resource> result) {
+		Set<ClassPathManifestEntry> entries = classPathManifestEntriesCache;
+		if (entries == null) {
+			entries = getClassPathManifestEntries();
+			classPathManifestEntriesCache = entries;
+		}
+		for (ClassPathManifestEntry entry : entries) {
+			if (!result.contains(entry.resource()) &&
+					(entry.alternative() != null && !result.contains(entry.alternative()))) {
+				result.add(entry.resource());
+			}
+		}
+	}
+
+	private Set<ClassPathManifestEntry> getClassPathManifestEntries() {
+		Set<ClassPathManifestEntry> manifestEntries = new HashSet<>();
+		Set<File> seen = new HashSet<>();
 		try {
-			String javaClassPathProperty = System.getProperty("java.class.path");
-			for (String path : StringUtils.delimitedListToStringArray(javaClassPathProperty, File.pathSeparator)) {
+			String paths = System.getProperty("java.class.path");
+			for (String path : StringUtils.delimitedListToStringArray(paths, File.pathSeparator)) {
 				try {
-					String filePath = new File(path).getAbsolutePath();
-					int prefixIndex = filePath.indexOf(':');
-					if (prefixIndex == 1) {
-						// Possibly a drive prefix on Windows (for example, "c:"), so we prepend a slash
-						// and convert the drive letter to uppercase for consistent duplicate detection.
-						filePath = "/" + StringUtils.capitalize(filePath);
-					}
-					// Since '#' can appear in directories/filenames, java.net.URL should not treat it as a fragment
-					filePath = StringUtils.replace(filePath, "#", "%23");
-					// Build URL that points to the root of the jar file
-					UrlResource jarResource = new UrlResource(ResourceUtils.JAR_URL_PREFIX +
-							ResourceUtils.FILE_URL_PREFIX + filePath + ResourceUtils.JAR_URL_SEPARATOR);
-					// Potentially overlapping with URLClassLoader.getURLs() result in addAllClassLoaderJarRoots().
-					if (!result.contains(jarResource) && !hasDuplicate(filePath, result) && jarResource.exists()) {
-						result.add(jarResource);
+					File jar = new File(path).getAbsoluteFile();
+					if (jar.isFile() && seen.add(jar)) {
+						manifestEntries.add(ClassPathManifestEntry.of(jar));
+						manifestEntries.addAll(getClassPathManifestEntriesFromJar(jar));
 					}
 				}
 				catch (MalformedURLException ex) {
@@ -550,34 +563,45 @@ public class PathMatchingResourcePatternResolver implements ResourcePatternResol
 					}
 				}
 			}
+			return Collections.unmodifiableSet(manifestEntries);
 		}
 		catch (Exception ex) {
 			if (logger.isDebugEnabled()) {
 				logger.debug("Failed to evaluate 'java.class.path' manifest entries: " + ex);
 			}
+			return Collections.emptySet();
 		}
 	}
 
-	/**
-	 * Check whether the given file path has a duplicate but differently structured entry
-	 * in the existing result, i.e. with or without a leading slash.
-	 * @param filePath the file path (with or without a leading slash)
-	 * @param result the current result
-	 * @return {@code true} if there is a duplicate (i.e. to ignore the given file path),
-	 * {@code false} to proceed with adding a corresponding resource to the current result
-	 */
-	private boolean hasDuplicate(String filePath, Set<Resource> result) {
-		if (result.isEmpty()) {
-			return false;
-		}
-		String duplicatePath = (filePath.startsWith("/") ? filePath.substring(1) : "/" + filePath);
-		try {
-			return result.contains(new UrlResource(ResourceUtils.JAR_URL_PREFIX + ResourceUtils.FILE_URL_PREFIX +
-					duplicatePath + ResourceUtils.JAR_URL_SEPARATOR));
+	private Set<ClassPathManifestEntry> getClassPathManifestEntriesFromJar(File jar) throws IOException {
+		URL base = jar.toURI().toURL();
+		File parent = jar.getAbsoluteFile().getParentFile();
+		try (JarFile jarFile = new JarFile(jar)) {
+			Manifest manifest = jarFile.getManifest();
+			Attributes attributes = (manifest != null) ? manifest.getMainAttributes() : null;
+			String classPath = (attributes != null) ? attributes.getValue(Name.CLASS_PATH) : null;
+			Set<ClassPathManifestEntry> manifestEntries = new HashSet<>();
+			if (StringUtils.hasLength(classPath)) {
+				StringTokenizer tokenizer = new StringTokenizer(classPath);
+				while (tokenizer.hasMoreTokens()) {
+					String path = tokenizer.nextToken();
+					if (path.indexOf(':') >= 0 && !"file".equalsIgnoreCase(new URL(base, path).getProtocol())) {
+						// See jdk.internal.loader.URLClassPath.JarLoader.tryResolveFile(URL, String)
+						continue;
+					}
+					File candidate = new File(parent, path);
+					if (candidate.isFile() && candidate.getCanonicalPath().contains(parent.getCanonicalPath())) {
+						manifestEntries.add(ClassPathManifestEntry.of(candidate));
+					}
+				}
+			}
+			return Collections.unmodifiableSet(manifestEntries);
 		}
-		catch (MalformedURLException ex) {
-			// Ignore: just for testing against duplicate.
-			return false;
+		catch (Exception ex) {
+			if (logger.isDebugEnabled()) {
+				logger.debug("Failed to load manifest entries from jar file '" + jar + "': " + ex);
+			}
+			return Collections.emptySet();
 		}
 	}
 
@@ -1170,4 +1194,51 @@ public class PathMatchingResourcePatternResolver implements ResourcePatternResol
 		}
 	}
 
+
+	/**
+	 * A single {@code Class-Path} manifest entry.
+	 */
+	private record ClassPathManifestEntry(Resource resource, @Nullable Resource alternative) {
+
+		private static final String JARFILE_URL_PREFIX = ResourceUtils.JAR_URL_PREFIX + ResourceUtils.FILE_URL_PREFIX;
+
+		static ClassPathManifestEntry of(File file) throws MalformedURLException {
+			String path = fixPath(file.getAbsolutePath());
+			Resource resource = asJarFileResource(path);
+			Resource alternative = createAlternative(path);
+			return new ClassPathManifestEntry(resource, alternative);
+		}
+
+		private static String fixPath(String path) {
+			int prefixIndex = path.indexOf(':');
+			if (prefixIndex == 1) {
+				// Possibly a drive prefix on Windows (for example, "c:"), so we prepend a slash
+				// and convert the drive letter to uppercase for consistent duplicate detection.
+				path = "/" + StringUtils.capitalize(path);
+			}
+			// Since '#' can appear in directories/filenames, java.net.URL should not treat it as a fragment
+			return StringUtils.replace(path, "#", "%23");
+		}
+
+		/**
+		 * Return a alternative form of the resource, i.e. with or without a leading slash.
+		 * @param path the file path (with or without a leading slash)
+		 * @return the alternative form or {@code null}
+		 */
+		@Nullable
+		private static Resource createAlternative(String path) {
+			try {
+				String alternativePath = path.startsWith("/") ? path.substring(1) : "/" + path;
+				return asJarFileResource(alternativePath);
+			}
+			catch (MalformedURLException ex) {
+				return null;
+			}
+		}
+
+		private static Resource asJarFileResource(String path)
+				throws MalformedURLException {
+			return new UrlResource(JARFILE_URL_PREFIX + path + ResourceUtils.JAR_URL_SEPARATOR);
+		}
+	}
 }

spring-core/src/test/java/org/springframework/core/io/support/ClassPathManifestEntriesTestApplication.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2002-2024 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.core.io.support;
+
+import java.io.IOException;
+import java.util.List;
+
+/**
+ * Class packaged into a temporary jar to test
+ * {@link PathMatchingResourcePatternResolver} detection of classpath manifest
+ * entries.
+ *
+ * @author Phillip Webb
+ */
+public class ClassPathManifestEntriesTestApplication {
+
+	public static void main(String[] args) throws IOException {
+		PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
+		System.out.println("!!!!" + List.of(resolver.getResources("classpath*:/**/*.txt")));
+	}
+
+}

spring-core/src/test/java/org/springframework/core/io/support/PathMatchingResourcePatternResolverTests.java

@@ -16,23 +16,44 @@
 
 package org.springframework.core.io.support;
 
+import java.io.File;
 import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.UncheckedIOException;
+import java.net.JarURLConnection;
+import java.net.URISyntaxException;
 import java.net.URL;
 import java.net.URLClassLoader;
+import java.net.URLConnection;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.Arrays;
+import java.util.Enumeration;
 import java.util.List;
+import java.util.jar.Attributes;
+import java.util.jar.Attributes.Name;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+import java.util.jar.JarOutputStream;
+import java.util.jar.Manifest;
 import java.util.stream.Collectors;
+import java.util.zip.ZipEntry;
 
+import org.apache.commons.logging.LogFactory;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
 
 import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.Resource;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.FileSystemUtils;
+import org.springframework.util.StreamUtils;
 import org.springframework.util.StringUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -278,6 +299,103 @@ class PathMatchingResourcePatternResolverTests {
 		}
 	}
 
+	@Nested
+	class ClassPathManifestEntries {
+
+		@TempDir
+		Path temp;
+
+		@Test
+		void javaDashJarFindsClassPathManifestEntries() throws Exception {
+			Path lib = this.temp.resolve("lib");
+			Files.createDirectories(lib);
+			writeAssetJar(lib.resolve("asset.jar"));
+			writeApplicationJar(this.temp.resolve("app.jar"));
+			String java = ProcessHandle.current().info().command().get();
+			Process process = new ProcessBuilder(java, "-jar", "app.jar")
+				.directory(this.temp.toFile())
+				.start();
+			assertThat(process.waitFor()).isZero();
+			String result = StreamUtils.copyToString(process.getInputStream(), StandardCharsets.UTF_8);
+			assertThat(result.replace("\\", "/")).contains("!!!!").contains("/lib/asset.jar!/assets/file.txt");
+		}
+
+		private void writeAssetJar(Path path) throws Exception {
+			try (JarOutputStream jar = new JarOutputStream(new FileOutputStream(path.toFile()))) {
+				jar.putNextEntry(new ZipEntry("assets/"));
+				jar.closeEntry();
+				jar.putNextEntry(new ZipEntry("assets/file.txt"));
+				StreamUtils.copy("test", StandardCharsets.UTF_8, jar);
+				jar.closeEntry();
+			}
+		}
+
+		private void writeApplicationJar(Path path) throws Exception {
+			Manifest manifest = new Manifest();
+			Attributes mainAttributes = manifest.getMainAttributes();
+			mainAttributes.put(Name.CLASS_PATH, buildSpringClassPath() + "lib/asset.jar");
+			mainAttributes.put(Name.MAIN_CLASS, ClassPathManifestEntriesTestApplication.class.getName());
+			mainAttributes.put(Name.MANIFEST_VERSION, "1.0");
+			try (JarOutputStream jar = new JarOutputStream(new FileOutputStream(path.toFile()), manifest)) {
+				String appClassResource = ClassUtils.convertClassNameToResourcePath(
+						ClassPathManifestEntriesTestApplication.class.getName())
+						+ ClassUtils.CLASS_FILE_SUFFIX;
+				String folder = "";
+				for (String name : appClassResource.split("/")) {
+					if (!name.endsWith(ClassUtils.CLASS_FILE_SUFFIX)) {
+						folder += name + "/";
+						jar.putNextEntry(new ZipEntry(folder));
+						jar.closeEntry();
+					}
+					else {
+						jar.putNextEntry(new ZipEntry(folder + name));
+						try (InputStream in = getClass().getResourceAsStream(name)) {
+							in.transferTo(jar);
+						}
+						jar.closeEntry();
+					}
+				}
+			}
+		}
+
+		private String buildSpringClassPath() throws Exception {
+			return copyClasses(PathMatchingResourcePatternResolver.class, "spring-core")
+					+ copyClasses(LogFactory.class, "commons-logging");
+		}
+
+		private String copyClasses(Class<?> sourceClass, String destinationName)
+				throws URISyntaxException, IOException {
+			Path destination = this.temp.resolve(destinationName);
+			String resourcePath = ClassUtils.convertClassNameToResourcePath(sourceClass.getName())
+					+ ClassUtils.CLASS_FILE_SUFFIX;
+			URL resource = getClass().getClassLoader().getResource(resourcePath);
+			URL url = new URL(resource.toString().replace(resourcePath, ""));
+			URLConnection connection = url.openConnection();
+			if (connection instanceof JarURLConnection jarUrlConnection) {
+				try (JarFile jarFile = jarUrlConnection.getJarFile()) {
+					Enumeration<JarEntry> entries = jarFile.entries();
+					while (entries.hasMoreElements()) {
+						JarEntry entry = entries.nextElement();
+						if (!entry.isDirectory()) {
+							Path entryPath = destination.resolve(entry.getName());
+							try (InputStream in = jarFile.getInputStream(entry)) {
+								Files.createDirectories(entryPath.getParent());
+								Files.copy(in, destination.resolve(entry.getName()));
+							}
+						}
+					}
+				}
+			}
+			else {
+				File source = new File(url.toURI());
+				Files.createDirectories(destination);
+				FileSystemUtils.copyRecursively(source, destination.toFile());
+			}
+			return destinationName + "/ ";
+		}
+
+	}
+
 
 	private void assertFilenames(String pattern, String... filenames) {
 		assertFilenames(pattern, false, filenames);