001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io;
018
019import java.io.File;
020import java.io.FileFilter;
021import java.io.IOException;
022import java.nio.file.Files;
023import java.util.Collection;
024import java.util.Objects;
025
026import org.apache.commons.io.file.PathUtils;
027import org.apache.commons.io.filefilter.FileFilterUtils;
028import org.apache.commons.io.filefilter.IOFileFilter;
029import org.apache.commons.io.filefilter.TrueFileFilter;
030
031/**
032 * Abstract class that walks through a directory hierarchy and provides subclasses with convenient hooks to add specific
033 * behavior.
034 * <p>
035 * This class operates with a {@link FileFilter} and maximum depth to limit the files and directories visited. Commons
036 * IO supplies many common filter implementations in the <a href="filefilter/package-summary.html"> filefilter</a>
037 * package.
038 * </p>
039 * <p>
040 * The following sections describe:
041 * </p>
042 * <ul>
043 * <li><a href="#example">1. Example Implementation</a> - example {@link FileCleaner} implementation.</li>
044 * <li><a href="#filter">2. Filter Example</a> - using {@link FileFilter}(s) with {@link DirectoryWalker}.</li>
045 * <li><a href="#cancel">3. Cancellation</a> - how to implement cancellation behavior.</li>
046 * </ul>
047 *
048 * <h2 id="example">1. Example Implementation</h2>
049 *
050 * There are many possible extensions, for example, to delete all files and '.svn' directories, and return a list of
051 * deleted files:
052 *
053 * <pre>
054 * public class FileCleaner extends DirectoryWalker {
055 *
056 *     public FileCleaner() {
057 *         super();
058 *     }
059 *
060 *     public List clean(File startDirectory) {
061 *         List results = new ArrayList();
062 *         walk(startDirectory, results);
063 *         return results;
064 *     }
065 *
066 *     protected boolean handleDirectory(File directory, int depth, Collection results) {
067 *         // delete svn directories and then skip
068 *         if (".svn".equals(directory.getName())) {
069 *             directory.delete();
070 *             return false;
071 *         } else {
072 *             return true;
073 *         }
074 *
075 *     }
076 *
077 *     protected void handleFile(File file, int depth, Collection results) {
078 *         // delete file and add to list of deleted
079 *         file.delete();
080 *         results.add(file);
081 *     }
082 * }
083 * </pre>
084 *
085 * <h2 id="filter">2. Filter Example</h2>
086 *
087 * <p>
088 * Choosing which directories and files to process can be a key aspect of using this class. This information can be
089 * setup in three ways, via three different constructors.
090 * </p>
091 * <p>
092 * The first option is to visit all directories and files. This is achieved via the no-args constructor.
093 * </p>
094 * <p>
095 * The second constructor option is to supply a single {@link FileFilter} that describes the files and directories to
096 * visit. Care must be taken with this option as the same filter is used for both directories and files.
097 * </p>
098 * <p>
099 * For example, if you wanted all directories which are not hidden and files which end in ".txt":
100 * </p>
101 *
102 * <pre>
103 * public class FooDirectoryWalker extends DirectoryWalker {
104 *     public FooDirectoryWalker(FileFilter filter) {
105 *         super(filter, -1);
106 *     }
107 * }
108 *
109 * // Build up the filters and create the walker
110 * // Create a filter for Non-hidden directories
111 * IOFileFilter fooDirFilter = FileFilterUtils.andFileFilter(FileFilterUtils.directoryFileFilter,
112 *     HiddenFileFilter.VISIBLE);
113 *
114 * // Create a filter for Files ending in ".txt"
115 * IOFileFilter fooFileFilter = FileFilterUtils.andFileFilter(FileFilterUtils.fileFileFilter,
116 *     FileFilterUtils.suffixFileFilter(".txt"));
117 *
118 * // Combine the directory and file filters using an OR condition
119 * java.io.FileFilter fooFilter = FileFilterUtils.orFileFilter(fooDirFilter, fooFileFilter);
120 *
121 * // Use the filter to construct a DirectoryWalker implementation
122 * FooDirectoryWalker walker = new FooDirectoryWalker(fooFilter);
123 * </pre>
124 * <p>
125 * The third constructor option is to specify separate filters, one for directories and one for files. These are
126 * combined internally to form the correct {@link FileFilter}, something which is very easy to get wrong when
127 * attempted manually, particularly when trying to express constructs like 'any file in directories named docs'.
128 * </p>
129 * <p>
130 * For example, if you wanted all directories which are not hidden and files which end in ".txt":
131 * </p>
132 *
133 * <pre>
134 *  public class FooDirectoryWalker extends DirectoryWalker {
135 *    public FooDirectoryWalker(IOFileFilter dirFilter, IOFileFilter fileFilter) {
136 *      super(dirFilter, fileFilter, -1);
137 *    }
138 *  }
139 *
140 *  // Use the filters to construct the walker
141 *  FooDirectoryWalker walker = new FooDirectoryWalker(
142 *    HiddenFileFilter.VISIBLE,
143 *    FileFilterUtils.suffixFileFilter(".txt"),
144 *  );
145 * </pre>
146 * <p>
147 * This is much simpler than the previous example, and is why it is the preferred option for filtering.
148 * </p>
149 *
150 * <h2 id="cancel">3. Cancellation</h2>
151 *
152 * <p>
153 * The DirectoryWalker contains some of the logic required for cancel processing. Subclasses must complete the
154 * implementation.
155 * </p>
156 * <p>
157 * What {@link DirectoryWalker} does provide for cancellation is:
158 * </p>
159 * <ul>
160 * <li>{@link CancelException} which can be thrown in any of the <i>lifecycle</i> methods to stop processing.</li>
161 * <li>The {@code walk()} method traps thrown {@link CancelException} and calls the {@code handleCancelled()}
162 * method, providing a place for custom cancel processing.</li>
163 * </ul>
164 * <p>
165 * Implementations need to provide:
166 * </p>
167 * <ul>
168 * <li>The decision logic on whether to cancel processing or not.</li>
169 * <li>Constructing and throwing a {@link CancelException}.</li>
170 * <li>Custom cancel processing in the {@code handleCancelled()} method.
171 * </ul>
172 * <p>
173 * Two possible scenarios are envisaged for cancellation:
174 * </p>
175 * <ul>
176 * <li><a href="#external">3.1 External / Multi-threaded</a> - cancellation being decided/initiated by an external
177 * process.</li>
178 * <li><a href="#internal">3.2 Internal</a> - cancellation being decided/initiated from within a DirectoryWalker
179 * implementation.</li>
180 * </ul>
181 * <p>
182 * The following sections provide example implementations for these two different scenarios.
183 * </p>
184 *
185 * <h3 id="external">3.1 External / Multi-threaded</h3>
186 *
187 * <p>
188 * This example provides a public {@code cancel()} method that can be called by another thread to stop the
189 * processing. A typical example use-case would be a cancel button on a GUI. Calling this method sets a
190 * <a href="http://java.sun.com/docs/books/jls/second_edition/html/classes.doc.html#36930"> volatile</a> flag to ensure
191 * it will work properly in a multi-threaded environment. The flag is returned by the {@code handleIsCancelled()}
192 * method, which will cause the walk to stop immediately. The {@code handleCancelled()} method will be the next,
193 * and last, callback method received once cancellation has occurred.
194 * </p>
195 *
196 * <pre>
197 * public class FooDirectoryWalker extends DirectoryWalker {
198 *
199 *     private volatile boolean cancelled = false;
200 *
201 *     public void cancel() {
202 *         cancelled = true;
203 *     }
204 *
205 *     protected boolean handleIsCancelled(File file, int depth, Collection results) {
206 *         return cancelled;
207 *     }
208 *
209 *     protected void handleCancelled(File startDirectory, Collection results, CancelException cancel) {
210 *         // implement processing required when a cancellation occurs
211 *     }
212 * }
213 * </pre>
214 *
215 * <h3 id="internal">3.2 Internal</h3>
216 *
217 * <p>
218 * This shows an example of how internal cancellation processing could be implemented. <b>Note</b> the decision logic
219 * and throwing a {@link CancelException} could be implemented in any of the <i>lifecycle</i> methods.
220 * </p>
221 *
222 * <pre>
223 * public class BarDirectoryWalker extends DirectoryWalker {
224 *
225 *     protected boolean handleDirectory(File directory, int depth, Collection results) throws IOException {
226 *         // cancel if hidden directory
227 *         if (directory.isHidden()) {
228 *             throw new CancelException(file, depth);
229 *         }
230 *         return true;
231 *     }
232 *
233 *     protected void handleFile(File file, int depth, Collection results) throws IOException {
234 *         // cancel if read-only file
235 *         if (!file.canWrite()) {
236 *             throw new CancelException(file, depth);
237 *         }
238 *         results.add(file);
239 *     }
240 *
241 *     protected void handleCancelled(File startDirectory, Collection results, CancelException cancel) {
242 *         // implement processing required when a cancellation occurs
243 *     }
244 * }
245 * </pre>
246 *
247 * @param <T> The result type, like {@link File}.
248 * @since 1.3
249 * @deprecated Apache Commons IO no longer uses this class. Instead, use
250 *             {@link PathUtils#walk(java.nio.file.Path, org.apache.commons.io.file.PathFilter, int, boolean, java.nio.file.FileVisitOption...)}
251 *             or {@link Files#walkFileTree(java.nio.file.Path, java.util.Set, int, java.nio.file.FileVisitor)}, and
252 *             friends.
253 */
254@Deprecated
255public abstract class DirectoryWalker<T> {
256
257    /**
258     * CancelException is thrown in DirectoryWalker to cancel the current
259     * processing.
260     */
261    public static class CancelException extends IOException {
262
263        /** Serialization id. */
264        private static final long serialVersionUID = 1347339620135041008L;
265
266        /** The file being processed when the exception was thrown. */
267        private final File file;
268        /** The file depth when the exception was thrown. */
269        private final int depth;
270
271        /**
272         * Constructs a {@link CancelException} with
273         * the file and depth when cancellation occurred.
274         *
275         * @param file  the file when the operation was cancelled, may be null
276         * @param depth  the depth when the operation was cancelled, may be null
277         */
278        public CancelException(final File file, final int depth) {
279            this("Operation Cancelled", file, depth);
280        }
281
282        /**
283         * Constructs a {@link CancelException} with
284         * an appropriate message and the file and depth when
285         * cancellation occurred.
286         *
287         * @param message  the detail message
288         * @param file  the file when the operation was cancelled
289         * @param depth  the depth when the operation was cancelled
290         */
291        public CancelException(final String message, final File file, final int depth) {
292            super(message);
293            this.file = file;
294            this.depth = depth;
295        }
296
297        /**
298         * Returns the depth when the operation was cancelled.
299         *
300         * @return the depth when the operation was cancelled
301         */
302        public int getDepth() {
303            return depth;
304        }
305
306        /**
307         * Returns the file when the operation was cancelled.
308         *
309         * @return the file when the operation was cancelled
310         */
311        public File getFile() {
312            return file;
313        }
314    }
315    /**
316     * The file filter to use to filter files and directories.
317     */
318    private final FileFilter filter;
319
320    /**
321     * The limit on the directory depth to walk.
322     */
323    private final int depthLimit;
324
325    /**
326     * Constructs an instance with no filtering and unlimited <i>depth</i>.
327     */
328    protected DirectoryWalker() {
329        this(null, -1);
330    }
331
332    /**
333     * Constructs an instance with a filter and limit the <i>depth</i> navigated to.
334     * <p>
335     * The filter controls which files and directories will be navigated to as
336     * part of the walk. The {@link FileFilterUtils} class is useful for combining
337     * various filters together. A {@code null} filter means that no
338     * filtering should occur and all files and directories will be visited.
339     * </p>
340     *
341     * @param filter  the filter to apply, null means visit all files
342     * @param depthLimit  controls how <i>deep</i> the hierarchy is
343     *  navigated to (less than 0 means unlimited)
344     */
345    protected DirectoryWalker(final FileFilter filter, final int depthLimit) {
346        this.filter = filter;
347        this.depthLimit = depthLimit;
348    }
349
350    /**
351     * Constructs an instance with a directory and a file filter and an optional
352     * limit on the <i>depth</i> navigated to.
353     * <p>
354     * The filters control which files and directories will be navigated to as part
355     * of the walk. This constructor uses {@link FileFilterUtils#makeDirectoryOnly(IOFileFilter)}
356     * and {@link FileFilterUtils#makeFileOnly(IOFileFilter)} internally to combine the filters.
357     * A {@code null} filter means that no filtering should occur.
358     * </p>
359     *
360     * @param directoryFilter  the filter to apply to directories, null means visit all directories
361     * @param fileFilter  the filter to apply to files, null means visit all files
362     * @param depthLimit  controls how <i>deep</i> the hierarchy is
363     *  navigated to (less than 0 means unlimited)
364     */
365    protected DirectoryWalker(IOFileFilter directoryFilter, IOFileFilter fileFilter, final int depthLimit) {
366        if (directoryFilter == null && fileFilter == null) {
367            this.filter = null;
368        } else {
369            directoryFilter = directoryFilter != null ? directoryFilter : TrueFileFilter.TRUE;
370            fileFilter = fileFilter != null ? fileFilter : TrueFileFilter.TRUE;
371            directoryFilter = FileFilterUtils.makeDirectoryOnly(directoryFilter);
372            fileFilter = FileFilterUtils.makeFileOnly(fileFilter);
373            this.filter = directoryFilter.or(fileFilter);
374        }
375        this.depthLimit = depthLimit;
376    }
377
378    /**
379     * Checks whether the walk has been cancelled by calling {@link #handleIsCancelled},
380     * throwing a {@link CancelException} if it has.
381     * <p>
382     * Writers of subclasses should not normally call this method as it is called
383     * automatically by the walk of the tree. However, sometimes a single method,
384     * typically {@link #handleFile}, may take a long time to run. In that case,
385     * you may wish to check for cancellation by calling this method.
386     * </p>
387     *
388     * @param file  the current file being processed
389     * @param depth  the current file level (starting directory = 0)
390     * @param results  the collection of result objects, may be updated
391     * @throws IOException if an I/O Error occurs
392     */
393    protected final void checkIfCancelled(final File file, final int depth, final Collection<T> results) throws
394            IOException {
395        if (handleIsCancelled(file, depth, results)) {
396            throw new CancelException(file, depth);
397        }
398    }
399
400    /**
401     * Overridable callback method invoked with the contents of each directory.
402     * <p>
403     * This implementation returns the files unchanged
404     * </p>
405     *
406     * @param directory  the current directory being processed
407     * @param depth  the current directory level (starting directory = 0)
408     * @param files the files (possibly filtered) in the directory, may be {@code null}
409     * @return the filtered list of files
410     * @throws IOException if an I/O Error occurs
411     * @since 2.0
412     */
413    @SuppressWarnings("unused") // Possibly thrown from subclasses.
414    protected File[] filterDirectoryContents(final File directory, final int depth, final File... files) throws
415            IOException {
416        return files;
417    }
418
419    /**
420     * Overridable callback method invoked when the operation is cancelled.
421     * The file being processed when the cancellation occurred can be
422     * obtained from the exception.
423     * <p>
424     * This implementation just re-throws the {@link CancelException}.
425     * </p>
426     *
427     * @param startDirectory  the directory that the walk started from
428     * @param results  the collection of result objects, may be updated
429     * @param cancel  the exception throw to cancel further processing
430     * containing details at the point of cancellation.
431     * @throws IOException if an I/O Error occurs
432     */
433    protected void handleCancelled(final File startDirectory, final Collection<T> results,
434                       final CancelException cancel) throws IOException {
435        // re-throw exception - overridable by subclass
436        throw cancel;
437    }
438
439    /**
440     * Overridable callback method invoked to determine if a directory should be processed.
441     * <p>
442     * This method returns a boolean to indicate if the directory should be examined or not.
443     * If you return false, the entire directory and any subdirectories will be skipped.
444     * Note that this functionality is in addition to the filtering by file filter.
445     * </p>
446     * <p>
447     * This implementation does nothing and returns true.
448     * </p>
449     *
450     * @param directory  the current directory being processed
451     * @param depth  the current directory level (starting directory = 0)
452     * @param results  the collection of result objects, may be updated
453     * @return true to process this directory, false to skip this directory
454     * @throws IOException if an I/O Error occurs
455     */
456    @SuppressWarnings("unused") // Possibly thrown from subclasses.
457    protected boolean handleDirectory(final File directory, final int depth, final Collection<T> results) throws
458            IOException {
459        // do nothing - overridable by subclass
460        return true;  // process directory
461    }
462
463    /**
464     * Overridable callback method invoked at the end of processing each directory.
465     * <p>
466     * This implementation does nothing.
467     * </p>
468     *
469     * @param directory  the directory being processed
470     * @param depth  the current directory level (starting directory = 0)
471     * @param results  the collection of result objects, may be updated
472     * @throws IOException if an I/O Error occurs
473     */
474    @SuppressWarnings("unused") // Possibly thrown from subclasses.
475    protected void handleDirectoryEnd(final File directory, final int depth, final Collection<T> results) throws
476            IOException {
477        // do nothing - overridable by subclass
478    }
479
480    /**
481     * Overridable callback method invoked at the start of processing each directory.
482     * <p>
483     * This implementation does nothing.
484     * </p>
485     *
486     * @param directory  the current directory being processed
487     * @param depth  the current directory level (starting directory = 0)
488     * @param results  the collection of result objects, may be updated
489     * @throws IOException if an I/O Error occurs
490     */
491    @SuppressWarnings("unused") // Possibly thrown from subclasses.
492    protected void handleDirectoryStart(final File directory, final int depth, final Collection<T> results) throws
493            IOException {
494        // do nothing - overridable by subclass
495    }
496
497    /**
498     * Overridable callback method invoked at the end of processing.
499     * <p>
500     * This implementation does nothing.
501     * </p>
502     *
503     * @param results  the collection of result objects, may be updated
504     * @throws IOException if an I/O Error occurs
505     */
506    @SuppressWarnings("unused") // Possibly thrown from subclasses.
507    protected void handleEnd(final Collection<T> results) throws IOException {
508        // do nothing - overridable by subclass
509    }
510
511    /**
512     * Overridable callback method invoked for each (non-directory) file.
513     * <p>
514     * This implementation does nothing.
515     * </p>
516     *
517     * @param file  the current file being processed
518     * @param depth  the current directory level (starting directory = 0)
519     * @param results  the collection of result objects, may be updated
520     * @throws IOException if an I/O Error occurs
521     */
522    @SuppressWarnings("unused") // Possibly thrown from subclasses.
523    protected void handleFile(final File file, final int depth, final Collection<T> results) throws IOException {
524        // do nothing - overridable by subclass
525    }
526
527    /**
528     * Overridable callback method invoked to determine if the entire walk
529     * operation should be immediately cancelled.
530     * <p>
531     * This method should be implemented by those subclasses that want to
532     * provide a public {@code cancel()} method available from another
533     * thread. The design pattern for the subclass should be as follows:
534     * </p>
535     * <pre>
536     *  public class FooDirectoryWalker extends DirectoryWalker {
537     *    private volatile boolean cancelled = false;
538     *
539     *    public void cancel() {
540     *        cancelled = true;
541     *    }
542     *    private void handleIsCancelled(File file, int depth, Collection results) {
543     *        return cancelled;
544     *    }
545     *    protected void handleCancelled(File startDirectory,
546     *              Collection results, CancelException cancel) {
547     *        // implement processing required when a cancellation occurs
548     *    }
549     *  }
550     * </pre>
551     * <p>
552     * If this method returns true, then the directory walk is immediately
553     * cancelled. The next callback method will be {@link #handleCancelled}.
554     * </p>
555     * <p>
556     * This implementation returns false.
557     * </p>
558     *
559     * @param file  the file or directory being processed
560     * @param depth  the current directory level (starting directory = 0)
561     * @param results  the collection of result objects, may be updated
562     * @return true if the walk has been cancelled
563     * @throws IOException if an I/O Error occurs
564     */
565    @SuppressWarnings("unused") // Possibly thrown from subclasses.
566    protected boolean handleIsCancelled(
567            final File file, final int depth, final Collection<T> results) throws IOException {
568        // do nothing - overridable by subclass
569        return false;  // not cancelled
570    }
571
572    /**
573     * Overridable callback method invoked for each restricted directory.
574     * <p>
575     * This implementation does nothing.
576     * </p>
577     *
578     * @param directory  the restricted directory
579     * @param depth  the current directory level (starting directory = 0)
580     * @param results  the collection of result objects, may be updated
581     * @throws IOException if an I/O Error occurs
582     */
583    @SuppressWarnings("unused") // Possibly thrown from subclasses.
584    protected void handleRestricted(final File directory, final int depth, final Collection<T> results) throws
585            IOException {
586        // do nothing - overridable by subclass
587    }
588
589    /**
590     * Overridable callback method invoked at the start of processing.
591     * <p>
592     * This implementation does nothing.
593     * </p>
594     *
595     * @param startDirectory  the directory to start from
596     * @param results  the collection of result objects, may be updated
597     * @throws IOException if an I/O Error occurs
598     */
599    @SuppressWarnings("unused") // Possibly thrown from subclasses.
600    protected void handleStart(final File startDirectory, final Collection<T> results) throws IOException {
601        // do nothing - overridable by subclass
602    }
603
604    /**
605     * Internal method that walks the directory hierarchy in a depth-first manner.
606     * <p>
607     * Users of this class do not need to call this method. This method will
608     * be called automatically by another (public) method on the specific subclass.
609     * </p>
610     * <p>
611     * Writers of subclasses should call this method to start the directory walk.
612     * Once called, this method will emit events as it walks the hierarchy.
613     * The event methods have the prefix {@code handle}.
614     * </p>
615     *
616     * @param startDirectory  the directory to start from, not null
617     * @param results  the collection of result objects, may be updated
618     * @throws NullPointerException if the start directory is null
619     * @throws IOException if an I/O Error occurs
620     */
621    protected final void walk(final File startDirectory, final Collection<T> results) throws IOException {
622        Objects.requireNonNull(startDirectory, "startDirectory");
623        try {
624            handleStart(startDirectory, results);
625            walk(startDirectory, 0, results);
626            handleEnd(results);
627        } catch (final CancelException cancel) {
628            handleCancelled(startDirectory, results, cancel);
629        }
630    }
631
632    /**
633     * Main recursive method to examine the directory hierarchy.
634     *
635     * @param directory  the directory to examine, not null
636     * @param depth  the directory level (starting directory = 0)
637     * @param results  the collection of result objects, may be updated
638     * @throws IOException if an I/O Error occurs
639     */
640    private void walk(final File directory, final int depth, final Collection<T> results) throws IOException {
641        checkIfCancelled(directory, depth, results);
642        if (handleDirectory(directory, depth, results)) {
643            handleDirectoryStart(directory, depth, results);
644            final int childDepth = depth + 1;
645            if (depthLimit < 0 || childDepth <= depthLimit) {
646                checkIfCancelled(directory, depth, results);
647                File[] childFiles = filter == null ? directory.listFiles() : directory.listFiles(filter);
648                childFiles = filterDirectoryContents(directory, depth, childFiles);
649                if (childFiles == null) {
650                    handleRestricted(directory, childDepth, results);
651                } else {
652                    for (final File childFile : childFiles) {
653                        if (childFile.isDirectory()) {
654                            walk(childFile, childDepth, results);
655                        } else {
656                            checkIfCancelled(childFile, childDepth, results);
657                            handleFile(childFile, childDepth, results);
658                            checkIfCancelled(childFile, childDepth, results);
659                        }
660                    }
661                }
662            }
663            handleDirectoryEnd(directory, depth, results);
664        }
665        checkIfCancelled(directory, depth, results);
666    }
667}