Package org.springframework.core.io.support

Source Code of org.springframework.core.io.support.PathMatchingResourcePatternResolver$PatternVirtualFileVisitor

/*
* Copyright 2002-2014 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
*
*      http://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.File;
import java.io.IOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.net.JarURLConnection;
import java.net.MalformedURLException;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLConnection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.io.UrlResource;
import org.springframework.core.io.VfsResource;
import org.springframework.util.AntPathMatcher;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.PathMatcher;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.ResourceUtils;
import org.springframework.util.StringUtils;

/**
* A {@link ResourcePatternResolver} implementation that is able to resolve a
* specified resource location path into one or more matching Resources.
* The source path may be a simple path which has a one-to-one mapping to a
* target {@link org.springframework.core.io.Resource}, or alternatively
* may contain the special "{@code classpath*:}" prefix and/or
* internal Ant-style regular expressions (matched using Spring's
* {@link org.springframework.util.AntPathMatcher} utility).
* Both of the latter are effectively wildcards.
*
* <p><b>No Wildcards:</b>
*
* <p>In the simple case, if the specified location path does not start with the
* {@code "classpath*:}" prefix, and does not contain a PathMatcher pattern,
* this resolver will simply return a single resource via a
* {@code getResource()} call on the underlying {@code ResourceLoader}.
* Examples are real URLs such as "{@code file:C:/context.xml}", pseudo-URLs
* such as "{@code classpath:/context.xml}", and simple unprefixed paths
* such as "{@code /WEB-INF/context.xml}". The latter will resolve in a
* fashion specific to the underlying {@code ResourceLoader} (e.g.
* {@code ServletContextResource} for a {@code WebApplicationContext}).
*
* <p><b>Ant-style Patterns:</b>
*
* <p>When the path location contains an Ant-style pattern, e.g.:
* <pre class="code">
* /WEB-INF/*-context.xml
* com/mycompany/**&#47;applicationContext.xml
* file:C:/some/path/*-context.xml
* classpath:com/mycompany/**&#47;applicationContext.xml</pre>
* the resolver follows a more complex but defined procedure to try to resolve
* the wildcard. It produces a {@code Resource} for the path up to the last
* non-wildcard segment and obtains a {@code URL} from it. If this URL is
* not a "{@code jar:}" URL or container-specific variant (e.g.
* "{@code zip:}" in WebLogic, "{@code wsjar}" in WebSphere", etc.),
* then a {@code java.io.File} is obtained from it, and used to resolve the
* wildcard by walking the filesystem. In the case of a jar URL, the resolver
* either gets a {@code java.net.JarURLConnection} from it, or manually parses
* the jar URL, and then traverses the contents of the jar file, to resolve the
* wildcards.
*
* <p><b>Implications on portability:</b>
*
* <p>If the specified path is already a file URL (either explicitly, or
* implicitly because the base {@code ResourceLoader} is a filesystem one,
* then wildcarding is guaranteed to work in a completely portable fashion.
*
* <p>If the specified path is a classpath location, then the resolver must
* obtain the last non-wildcard path segment URL via a
* {@code Classloader.getResource()} call. Since this is just a
* node of the path (not the file at the end) it is actually undefined
* (in the ClassLoader Javadocs) exactly what sort of a URL is returned in
* this case. In practice, it is usually a {@code java.io.File} representing
* the directory, where the classpath resource resolves to a filesystem
* location, or a jar URL of some sort, where the classpath resource resolves
* to a jar location. Still, there is a portability concern on this operation.
*
* <p>If a jar URL is obtained for the last non-wildcard segment, the resolver
* must be able to get a {@code java.net.JarURLConnection} from it, or
* manually parse the jar URL, to be able to walk the contents of the jar,
* and resolve the wildcard. This will work in most environments, but will
* fail in others, and it is strongly recommended that the wildcard
* resolution of resources coming from jars be thoroughly tested in your
* specific environment before you rely on it.
*
* <p><b>{@code classpath*:} Prefix:</b>
*
* <p>There is special support for retrieving multiple class path resources with
* the same name, via the "{@code classpath*:}" prefix. For example,
* "{@code classpath*:META-INF/beans.xml}" will find all "beans.xml"
* files in the class path, be it in "classes" directories or in JAR files.
* This is particularly useful for autodetecting config files of the same name
* at the same location within each jar file. Internally, this happens via a
* {@code ClassLoader.getResources()} call, and is completely portable.
*
* <p>The "classpath*:" prefix can also be combined with a PathMatcher pattern in
* the rest of the location path, for example "classpath*:META-INF/*-beans.xml".
* In this case, the resolution strategy is fairly simple: a
* {@code ClassLoader.getResources()} call is used on the last non-wildcard
* path segment to get all the matching resources in the class loader hierarchy,
* and then off each resource the same PathMatcher resolution strategy described
* above is used for the wildcard subpath.
*
* <p><b>Other notes:</b>
*
* <p><b>WARNING:</b> Note that "{@code classpath*:}" when combined with
* Ant-style patterns will only work reliably with at least one root directory
* before the pattern starts, unless the actual target files reside in the file
* system. This means that a pattern like "{@code classpath*:*.xml}" will
* <i>not</i> retrieve files from the root of jar files but rather only from the
* root of expanded directories. This originates from a limitation in the JDK's
* {@code ClassLoader.getResources()} method which only returns file system
* locations for a passed-in empty String (indicating potential roots to search).
*
* <p><b>WARNING:</b> Ant-style patterns with "classpath:" resources are not
* guaranteed to find matching resources if the root package to search is available
* in multiple class path locations. This is because a resource such as
* <pre class="code">
*     com/mycompany/package1/service-context.xml
* </pre>
* may be in only one location, but when a path such as
* <pre class="code">
*     classpath:com/mycompany/**&#47;service-context.xml
* </pre>
* is used to try to resolve it, the resolver will work off the (first) URL
* returned by {@code getResource("com/mycompany");}. If this base package
* node exists in multiple classloader locations, the actual end resource may
* not be underneath. Therefore, preferably, use "{@code classpath*:}" with the same
* Ant-style pattern in such a case, which will search <i>all</i> class path
* locations that contain the root package.
*
* @author Juergen Hoeller
* @author Colin Sampaleanu
* @author Marius Bogoevici
* @author Costin Leau
* @since 1.0.2
* @see #CLASSPATH_ALL_URL_PREFIX
* @see org.springframework.util.AntPathMatcher
* @see org.springframework.core.io.ResourceLoader#getResource(String)
* @see ClassLoader#getResources(String)
*/
public class PathMatchingResourcePatternResolver implements ResourcePatternResolver {

  private static final Log logger = LogFactory.getLog(PathMatchingResourcePatternResolver.class);

  private static Method equinoxResolveMethod;

  static {
    try {
      // Detect Equinox OSGi (e.g. on WebSphere 6.1)
      Class<?> fileLocatorClass = ClassUtils.forName("org.eclipse.core.runtime.FileLocator",
          PathMatchingResourcePatternResolver.class.getClassLoader());
      equinoxResolveMethod = fileLocatorClass.getMethod("resolve", URL.class);
      logger.debug("Found Equinox FileLocator for OSGi bundle URL resolution");
    }
    catch (Throwable ex) {
      equinoxResolveMethod = null;
    }
  }


  private final ResourceLoader resourceLoader;

  private PathMatcher pathMatcher = new AntPathMatcher();


  /**
   * Create a new PathMatchingResourcePatternResolver with a DefaultResourceLoader.
   * <p>ClassLoader access will happen via the thread context class loader.
   * @see org.springframework.core.io.DefaultResourceLoader
   */
  public PathMatchingResourcePatternResolver() {
    this.resourceLoader = new DefaultResourceLoader();
  }

  /**
   * Create a new PathMatchingResourcePatternResolver.
   * <p>ClassLoader access will happen via the thread context class loader.
   * @param resourceLoader the ResourceLoader to load root directories and
   * actual resources with
   */
  public PathMatchingResourcePatternResolver(ResourceLoader resourceLoader) {
    Assert.notNull(resourceLoader, "ResourceLoader must not be null");
    this.resourceLoader = resourceLoader;
  }

  /**
   * Create a new PathMatchingResourcePatternResolver with a DefaultResourceLoader.
   * @param classLoader the ClassLoader to load classpath resources with,
   * or {@code null} for using the thread context class loader
   * at the time of actual resource access
   * @see org.springframework.core.io.DefaultResourceLoader
   */
  public PathMatchingResourcePatternResolver(ClassLoader classLoader) {
    this.resourceLoader = new DefaultResourceLoader(classLoader);
  }


  /**
   * Return the ResourceLoader that this pattern resolver works with.
   */
  public ResourceLoader getResourceLoader() {
    return this.resourceLoader;
  }

  @Override
  public ClassLoader getClassLoader() {
    return getResourceLoader().getClassLoader();
  }

  /**
   * Set the PathMatcher implementation to use for this
   * resource pattern resolver. Default is AntPathMatcher.
   * @see org.springframework.util.AntPathMatcher
   */
  public void setPathMatcher(PathMatcher pathMatcher) {
    Assert.notNull(pathMatcher, "PathMatcher must not be null");
    this.pathMatcher = pathMatcher;
  }

  /**
   * Return the PathMatcher that this resource pattern resolver uses.
   */
  public PathMatcher getPathMatcher() {
    return this.pathMatcher;
  }


  @Override
  public Resource getResource(String location) {
    return getResourceLoader().getResource(location);
  }

  @Override
  public Resource[] getResources(String locationPattern) throws IOException {
    Assert.notNull(locationPattern, "Location pattern must not be null");
    if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {
      // a class path resource (multiple resources for same name possible)
      if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) {
        // a class path resource pattern
        return findPathMatchingResources(locationPattern);
      }
      else {
        // all class path resources with the given name
        return findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));
      }
    }
    else {
      // Only look for a pattern after a prefix here
      // (to not get fooled by a pattern symbol in a strange prefix).
      int prefixEnd = locationPattern.indexOf(":") + 1;
      if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {
        // a file pattern
        return findPathMatchingResources(locationPattern);
      }
      else {
        // a single resource with the given name
        return new Resource[] {getResourceLoader().getResource(locationPattern)};
      }
    }
  }

  /**
   * Find all class location resources with the given location via the ClassLoader.
   * Delegates to {@link #doFindAllClassPathResources(String)}.
   * @param location the absolute path within the classpath
   * @return the result as Resource array
   * @throws IOException in case of I/O errors
   * @see java.lang.ClassLoader#getResources
   * @see #convertClassLoaderURL
   */
  protected Resource[] findAllClassPathResources(String location) throws IOException {
    String path = location;
    if (path.startsWith("/")) {
      path = path.substring(1);
    }
    Set<Resource> result = doFindAllClassPathResources(path);
    return result.toArray(new Resource[result.size()]);
  }

  /**
   * Find all class location resources with the given path via the ClassLoader.
   * Called by {@link #findAllClassPathResources(String)}.
   * @param path the absolute path within the classpath (never a leading slash)
   * @return a mutable Set of matching Resource instances
   */
  protected Set<Resource> doFindAllClassPathResources(String path) throws IOException {
    Set<Resource> result = new LinkedHashSet<Resource>(16);
    ClassLoader cl = getClassLoader();
    Enumeration<URL> resourceUrls = (cl != null ? cl.getResources(path) : ClassLoader.getSystemResources(path));
    while (resourceUrls.hasMoreElements()) {
      URL url = resourceUrls.nextElement();
      result.add(convertClassLoaderURL(url));
    }
    if ("".equals(path)) {
      // The above result is likely to be incomplete, i.e. only containing file system references.
      // We need to have pointers to each of the jar files on the classpath as well...
      addAllClassLoaderJarRoots(cl, result);
    }
    return result;
  }

  /**
   * Convert the given URL as returned from the ClassLoader into a {@link Resource}.
   * <p>The default implementation simply creates a {@link UrlResource} instance.
   * @param url a URL as returned from the ClassLoader
   * @return the corresponding Resource object
   * @see java.lang.ClassLoader#getResources
   * @see org.springframework.core.io.Resource
   */
  protected Resource convertClassLoaderURL(URL url) {
    return new UrlResource(url);
  }

  /**
   * Search all {@link URLClassLoader} URLs for jar file references and add them to the
   * given set of resources in the form of pointers to the root of the jar file content.
   * @param classLoader the ClassLoader to search (including its ancestors)
   * @param result the set of resources to add jar roots to
   */
  protected void addAllClassLoaderJarRoots(ClassLoader classLoader, Set<Resource> result) {
    if (classLoader instanceof URLClassLoader) {
      try {
        for (URL url : ((URLClassLoader) classLoader).getURLs()) {
          if (ResourceUtils.isJarFileURL(url)) {
            try {
              UrlResource jarResource = new UrlResource(
                  ResourceUtils.JAR_URL_PREFIX + url.toString() + ResourceUtils.JAR_URL_SEPARATOR);
              if (jarResource.exists()) {
                result.add(jarResource);
              }
            }
            catch (MalformedURLException ex) {
              if (logger.isDebugEnabled()) {
                logger.debug("Cannot search for matching files underneath [" + url +
                    "] because it cannot be converted to a valid 'jar:' URL: " + ex.getMessage());
              }
            }
          }
        }
      }
      catch (Exception ex) {
        if (logger.isDebugEnabled()) {
          logger.debug("Cannot introspect jar files since ClassLoader [" + classLoader +
              "] does not support 'getURLs()': " + ex);
        }
      }
    }
    if (classLoader != null) {
      try {
        addAllClassLoaderJarRoots(classLoader.getParent(), result);
      }
      catch (Exception ex) {
        if (logger.isDebugEnabled()) {
          logger.debug("Cannot introspect jar files in parent ClassLoader since [" + classLoader +
              "] does not support 'getParent()': " + ex);
        }
      }
    }
  }

  /**
   * Find all resources that match the given location pattern via the
   * Ant-style PathMatcher. Supports resources in jar files and zip files
   * and in the file system.
   * @param locationPattern the location pattern to match
   * @return the result as Resource array
   * @throws IOException in case of I/O errors
   * @see #doFindPathMatchingJarResources
   * @see #doFindPathMatchingFileResources
   * @see org.springframework.util.PathMatcher
   */
  protected Resource[] findPathMatchingResources(String locationPattern) throws IOException {
    String rootDirPath = determineRootDir(locationPattern);
    String subPattern = locationPattern.substring(rootDirPath.length());
    Resource[] rootDirResources = getResources(rootDirPath);
    Set<Resource> result = new LinkedHashSet<Resource>(16);
    for (Resource rootDirResource : rootDirResources) {
      rootDirResource = resolveRootDirResource(rootDirResource);
      if (rootDirResource.getURL().getProtocol().startsWith(ResourceUtils.URL_PROTOCOL_VFS)) {
        result.addAll(VfsResourceMatchingDelegate.findMatchingResources(rootDirResource, subPattern, getPathMatcher()));
      }
      else if (isJarResource(rootDirResource)) {
        result.addAll(doFindPathMatchingJarResources(rootDirResource, subPattern));
      }
      else {
        result.addAll(doFindPathMatchingFileResources(rootDirResource, subPattern));
      }
    }
    if (logger.isDebugEnabled()) {
      logger.debug("Resolved location pattern [" + locationPattern + "] to resources " + result);
    }
    return result.toArray(new Resource[result.size()]);
  }

  /**
   * Determine the root directory for the given location.
   * <p>Used for determining the starting point for file matching,
   * resolving the root directory location to a {@code java.io.File}
   * and passing it into {@code retrieveMatchingFiles}, with the
   * remainder of the location as pattern.
   * <p>Will return "/WEB-INF/" for the pattern "/WEB-INF/*.xml",
   * for example.
   * @param location the location to check
   * @return the part of the location that denotes the root directory
   * @see #retrieveMatchingFiles
   */
  protected String determineRootDir(String location) {
    int prefixEnd = location.indexOf(":") + 1;
    int rootDirEnd = location.length();
    while (rootDirEnd > prefixEnd && getPathMatcher().isPattern(location.substring(prefixEnd, rootDirEnd))) {
      rootDirEnd = location.lastIndexOf('/', rootDirEnd - 2) + 1;
    }
    if (rootDirEnd == 0) {
      rootDirEnd = prefixEnd;
    }
    return location.substring(0, rootDirEnd);
  }

  /**
   * Resolve the specified resource for path matching.
   * <p>The default implementation detects an Equinox OSGi "bundleresource:"
   * / "bundleentry:" URL and resolves it into a standard jar file URL that
   * can be traversed using Spring's standard jar file traversal algorithm.
   * @param original the resource to resolve
   * @return the resolved resource (may be identical to the passed-in resource)
   * @throws IOException in case of resolution failure
   */
  protected Resource resolveRootDirResource(Resource original) throws IOException {
    if (equinoxResolveMethod != null) {
      URL url = original.getURL();
      if (url.getProtocol().startsWith("bundle")) {
        return new UrlResource((URL) ReflectionUtils.invokeMethod(equinoxResolveMethod, null, url));
      }
    }
    return original;
  }

  /**
   * Return whether the given resource handle indicates a jar resource
   * that the {@code doFindPathMatchingJarResources} method can handle.
   * <p>The default implementation checks against the URL protocols
   * "jar", "zip" and "wsjar" (the latter are used by BEA WebLogic Server
   * and IBM WebSphere, respectively, but can be treated like jar files).
   * @param resource the resource handle to check
   * (usually the root directory to start path matching from)
   * @see #doFindPathMatchingJarResources
   * @see org.springframework.util.ResourceUtils#isJarURL
   */
  protected boolean isJarResource(Resource resource) throws IOException {
    return ResourceUtils.isJarURL(resource.getURL());
  }

  /**
   * Find all resources in jar files that match the given location pattern
   * via the Ant-style PathMatcher.
   * @param rootDirResource the root directory as Resource
   * @param subPattern the sub pattern to match (below the root directory)
   * @return a mutable Set of matching Resource instances
   * @throws IOException in case of I/O errors
   * @see java.net.JarURLConnection
   * @see org.springframework.util.PathMatcher
   */
  protected Set<Resource> doFindPathMatchingJarResources(Resource rootDirResource, String subPattern)
      throws IOException {

    URLConnection con = rootDirResource.getURL().openConnection();
    JarFile jarFile;
    String jarFileUrl;
    String rootEntryPath;
    boolean newJarFile = false;

    if (con instanceof JarURLConnection) {
      // Should usually be the case for traditional JAR files.
      JarURLConnection jarCon = (JarURLConnection) con;
      ResourceUtils.useCachesIfNecessary(jarCon);
      jarFile = jarCon.getJarFile();
      jarFileUrl = jarCon.getJarFileURL().toExternalForm();
      JarEntry jarEntry = jarCon.getJarEntry();
      rootEntryPath = (jarEntry != null ? jarEntry.getName() : "");
    }
    else {
      // No JarURLConnection -> need to resort to URL file parsing.
      // We'll assume URLs of the format "jar:path!/entry", with the protocol
      // being arbitrary as long as following the entry format.
      // We'll also handle paths with and without leading "file:" prefix.
      String urlFile = rootDirResource.getURL().getFile();
      int separatorIndex = urlFile.indexOf(ResourceUtils.JAR_URL_SEPARATOR);
      if (separatorIndex != -1) {
        jarFileUrl = urlFile.substring(0, separatorIndex);
        rootEntryPath = urlFile.substring(separatorIndex + ResourceUtils.JAR_URL_SEPARATOR.length());
        jarFile = getJarFile(jarFileUrl);
      }
      else {
        jarFile = new JarFile(urlFile);
        jarFileUrl = urlFile;
        rootEntryPath = "";
      }
      newJarFile = true;
    }

    try {
      if (logger.isDebugEnabled()) {
        logger.debug("Looking for matching resources in jar file [" + jarFileUrl + "]");
      }
      if (!"".equals(rootEntryPath) && !rootEntryPath.endsWith("/")) {
        // Root entry path must end with slash to allow for proper matching.
        // The Sun JRE does not return a slash here, but BEA JRockit does.
        rootEntryPath = rootEntryPath + "/";
      }
      Set<Resource> result = new LinkedHashSet<Resource>(8);
      for (Enumeration<JarEntry> entries = jarFile.entries(); entries.hasMoreElements();) {
        JarEntry entry = entries.nextElement();
        String entryPath = entry.getName();
        if (entryPath.startsWith(rootEntryPath)) {
          String relativePath = entryPath.substring(rootEntryPath.length());
          if (getPathMatcher().match(subPattern, relativePath)) {
            result.add(rootDirResource.createRelative(relativePath));
          }
        }
      }
      return result;
    }
    finally {
      // Close jar file, but only if freshly obtained -
      // not from JarURLConnection, which might cache the file reference.
      if (newJarFile) {
        jarFile.close();
      }
    }
  }

  /**
   * Resolve the given jar file URL into a JarFile object.
   */
  protected JarFile getJarFile(String jarFileUrl) throws IOException {
    if (jarFileUrl.startsWith(ResourceUtils.FILE_URL_PREFIX)) {
      try {
        return new JarFile(ResourceUtils.toURI(jarFileUrl).getSchemeSpecificPart());
      }
      catch (URISyntaxException ex) {
        // Fallback for URLs that are not valid URIs (should hardly ever happen).
        return new JarFile(jarFileUrl.substring(ResourceUtils.FILE_URL_PREFIX.length()));
      }
    }
    else {
      return new JarFile(jarFileUrl);
    }
  }

  /**
   * Find all resources in the file system that match the given location pattern
   * via the Ant-style PathMatcher.
   * @param rootDirResource the root directory as Resource
   * @param subPattern the sub pattern to match (below the root directory)
   * @return a mutable Set of matching Resource instances
   * @throws IOException in case of I/O errors
   * @see #retrieveMatchingFiles
   * @see org.springframework.util.PathMatcher
   */
  protected Set<Resource> doFindPathMatchingFileResources(Resource rootDirResource, String subPattern)
      throws IOException {

    File rootDir;
    try {
      rootDir = rootDirResource.getFile().getAbsoluteFile();
    }
    catch (IOException ex) {
      if (logger.isWarnEnabled()) {
        logger.warn("Cannot search for matching files underneath " + rootDirResource +
            " because it does not correspond to a directory in the file system", ex);
      }
      return Collections.emptySet();
    }
    return doFindMatchingFileSystemResources(rootDir, subPattern);
  }

  /**
   * Find all resources in the file system that match the given location pattern
   * via the Ant-style PathMatcher.
   * @param rootDir the root directory in the file system
   * @param subPattern the sub pattern to match (below the root directory)
   * @return a mutable Set of matching Resource instances
   * @throws IOException in case of I/O errors
   * @see #retrieveMatchingFiles
   * @see org.springframework.util.PathMatcher
   */
  protected Set<Resource> doFindMatchingFileSystemResources(File rootDir, String subPattern) throws IOException {
    if (logger.isDebugEnabled()) {
      logger.debug("Looking for matching resources in directory tree [" + rootDir.getPath() + "]");
    }
    Set<File> matchingFiles = retrieveMatchingFiles(rootDir, subPattern);
    Set<Resource> result = new LinkedHashSet<Resource>(matchingFiles.size());
    for (File file : matchingFiles) {
      result.add(new FileSystemResource(file));
    }
    return result;
  }

  /**
   * Retrieve files that match the given path pattern,
   * checking the given directory and its subdirectories.
   * @param rootDir the directory to start from
   * @param pattern the pattern to match against,
   * relative to the root directory
   * @return a mutable Set of matching Resource instances
   * @throws IOException if directory contents could not be retrieved
   */
  protected Set<File> retrieveMatchingFiles(File rootDir, String pattern) throws IOException {
    if (!rootDir.exists()) {
      // Silently skip non-existing directories.
      if (logger.isDebugEnabled()) {
        logger.debug("Skipping [" + rootDir.getAbsolutePath() + "] because it does not exist");
      }
      return Collections.emptySet();
    }
    if (!rootDir.isDirectory()) {
      // Complain louder if it exists but is no directory.
      if (logger.isWarnEnabled()) {
        logger.warn("Skipping [" + rootDir.getAbsolutePath() + "] because it does not denote a directory");
      }
      return Collections.emptySet();
    }
    if (!rootDir.canRead()) {
      if (logger.isWarnEnabled()) {
        logger.warn("Cannot search for matching files underneath directory [" + rootDir.getAbsolutePath() +
            "] because the application is not allowed to read the directory");
      }
      return Collections.emptySet();
    }
    String fullPattern = StringUtils.replace(rootDir.getAbsolutePath(), File.separator, "/");
    if (!pattern.startsWith("/")) {
      fullPattern += "/";
    }
    fullPattern = fullPattern + StringUtils.replace(pattern, File.separator, "/");
    Set<File> result = new LinkedHashSet<File>(8);
    doRetrieveMatchingFiles(fullPattern, rootDir, result);
    return result;
  }

  /**
   * Recursively retrieve files that match the given pattern,
   * adding them to the given result list.
   * @param fullPattern the pattern to match against,
   * with prepended root directory path
   * @param dir the current directory
   * @param result the Set of matching File instances to add to
   * @throws IOException if directory contents could not be retrieved
   */
  protected void doRetrieveMatchingFiles(String fullPattern, File dir, Set<File> result) throws IOException {
    if (logger.isDebugEnabled()) {
      logger.debug("Searching directory [" + dir.getAbsolutePath() +
          "] for files matching pattern [" + fullPattern + "]");
    }
    File[] dirContents = dir.listFiles();
    if (dirContents == null) {
      if (logger.isWarnEnabled()) {
        logger.warn("Could not retrieve contents of directory [" + dir.getAbsolutePath() + "]");
      }
      return;
    }
    for (File content : dirContents) {
      String currPath = StringUtils.replace(content.getAbsolutePath(), File.separator, "/");
      if (content.isDirectory() && getPathMatcher().matchStart(fullPattern, currPath + "/")) {
        if (!content.canRead()) {
          if (logger.isDebugEnabled()) {
            logger.debug("Skipping subdirectory [" + dir.getAbsolutePath() +
                "] because the application is not allowed to read the directory");
          }
        }
        else {
          doRetrieveMatchingFiles(fullPattern, content, result);
        }
      }
      if (getPathMatcher().match(fullPattern, currPath)) {
        result.add(content);
      }
    }
  }


  /**
   * Inner delegate class, avoiding a hard JBoss VFS API dependency at runtime.
   */
  private static class VfsResourceMatchingDelegate {

    public static Set<Resource> findMatchingResources(
        Resource rootResource, String locationPattern, PathMatcher pathMatcher) throws IOException {
      Object root = VfsPatternUtils.findRoot(rootResource.getURL());
      PatternVirtualFileVisitor visitor =
          new PatternVirtualFileVisitor(VfsPatternUtils.getPath(root), locationPattern, pathMatcher);
      VfsPatternUtils.visit(root, visitor);
      return visitor.getResources();
    }
  }


  /**
   * VFS visitor for path matching purposes.
   */
  @SuppressWarnings("unused")
  private static class PatternVirtualFileVisitor implements InvocationHandler {

    private final String subPattern;

    private final PathMatcher pathMatcher;

    private final String rootPath;

    private final Set<Resource> resources = new LinkedHashSet<Resource>();

    public PatternVirtualFileVisitor(String rootPath, String subPattern, PathMatcher pathMatcher) {
      this.subPattern = subPattern;
      this.pathMatcher = pathMatcher;
      this.rootPath = (rootPath.length() == 0 || rootPath.endsWith("/") ? rootPath : rootPath + "/");
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      String methodName = method.getName();
      if (Object.class.equals(method.getDeclaringClass())) {
        if (methodName.equals("equals")) {
          // Only consider equal when proxies are identical.
          return (proxy == args[0]);
        }
        else if (methodName.equals("hashCode")) {
          return System.identityHashCode(proxy);
        }
      }
      else if ("getAttributes".equals(methodName)) {
        return getAttributes();
      }
      else if ("visit".equals(methodName)) {
        visit(args[0]);
        return null;
      }
      else if ("toString".equals(methodName)) {
        return toString();
      }

      throw new IllegalStateException("Unexpected method invocation: " + method);
    }

    public void visit(Object vfsResource) {
      if (this.pathMatcher.match(this.subPattern,
          VfsPatternUtils.getPath(vfsResource).substring(this.rootPath.length()))) {
        this.resources.add(new VfsResource(vfsResource));
      }
    }

    public Object getAttributes() {
      return VfsPatternUtils.getVisitorAttribute();
    }

    public Set<Resource> getResources() {
      return this.resources;
    }

    public int size() {
      return this.resources.size();
    }

    @Override
    public String toString() {
      return "sub-pattern: " + this.subPattern + ", resources: " + this.resources;
    }
  }

}
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