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 {@code FileCleaner} implementation.</li>
044 * <li><a href="#filter">2. Filter Example</a> - using {@link FileFilter}(s) with {@code 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 {@code 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 {@code 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     * The file filter to use to filter files and directories.
259     */
260    private final FileFilter filter;
261    /**
262     * The limit on the directory depth to walk.
263     */
264    private final int depthLimit;
265
266    /**
267     * Construct an instance with no filtering and unlimited <i>depth</i>.
268     */
269    protected DirectoryWalker() {
270        this(null, -1);
271    }
272
273    /**
274     * Constructs an instance with a filter and limit the <i>depth</i> navigated to.
275     * <p>
276     * The filter controls which files and directories will be navigated to as
277     * part of the walk. The {@link FileFilterUtils} class is useful for combining
278     * various filters together. A {@code null} filter means that no
279     * filtering should occur and all files and directories will be visited.
280     * </p>
281     *
282     * @param filter  the filter to apply, null means visit all files
283     * @param depthLimit  controls how <i>deep</i> the hierarchy is
284     *  navigated to (less than 0 means unlimited)
285     */
286    protected DirectoryWalker(final FileFilter filter, final int depthLimit) {
287        this.filter = filter;
288        this.depthLimit = depthLimit;
289    }
290
291    /**
292     * Constructs an instance with a directory and a file filter and an optional
293     * limit on the <i>depth</i> navigated to.
294     * <p>
295     * The filters control which files and directories will be navigated to as part
296     * of the walk. This constructor uses {@link FileFilterUtils#makeDirectoryOnly(IOFileFilter)}
297     * and {@link FileFilterUtils#makeFileOnly(IOFileFilter)} internally to combine the filters.
298     * A {@code null} filter means that no filtering should occur.
299     * </p>
300     *
301     * @param directoryFilter  the filter to apply to directories, null means visit all directories
302     * @param fileFilter  the filter to apply to files, null means visit all files
303     * @param depthLimit  controls how <i>deep</i> the hierarchy is
304     *  navigated to (less than 0 means unlimited)
305     */
306    protected DirectoryWalker(IOFileFilter directoryFilter, IOFileFilter fileFilter, final int depthLimit) {
307        if (directoryFilter == null && fileFilter == null) {
308            this.filter = null;
309        } else {
310            directoryFilter = directoryFilter != null ? directoryFilter : TrueFileFilter.TRUE;
311            fileFilter = fileFilter != null ? fileFilter : TrueFileFilter.TRUE;
312            directoryFilter = FileFilterUtils.makeDirectoryOnly(directoryFilter);
313            fileFilter = FileFilterUtils.makeFileOnly(fileFilter);
314            this.filter = directoryFilter.or(fileFilter);
315        }
316        this.depthLimit = depthLimit;
317    }
318
319    /**
320     * Internal method that walks the directory hierarchy in a depth-first manner.
321     * <p>
322     * Users of this class do not need to call this method. This method will
323     * be called automatically by another (public) method on the specific subclass.
324     * </p>
325     * <p>
326     * Writers of subclasses should call this method to start the directory walk.
327     * Once called, this method will emit events as it walks the hierarchy.
328     * The event methods have the prefix {@code handle}.
329     * </p>
330     *
331     * @param startDirectory  the directory to start from, not null
332     * @param results  the collection of result objects, may be updated
333     * @throws NullPointerException if the start directory is null
334     * @throws IOException if an I/O Error occurs
335     */
336    protected final void walk(final File startDirectory, final Collection<T> results) throws IOException {
337        Objects.requireNonNull(startDirectory, "startDirectory");
338        try {
339            handleStart(startDirectory, results);
340            walk(startDirectory, 0, results);
341            handleEnd(results);
342        } catch(final CancelException cancel) {
343            handleCancelled(startDirectory, results, cancel);
344        }
345    }
346
347    /**
348     * Main recursive method to examine the directory hierarchy.
349     *
350     * @param directory  the directory to examine, not null
351     * @param depth  the directory level (starting directory = 0)
352     * @param results  the collection of result objects, may be updated
353     * @throws IOException if an I/O Error occurs
354     */
355    private void walk(final File directory, final int depth, final Collection<T> results) throws IOException {
356        checkIfCancelled(directory, depth, results);
357        if (handleDirectory(directory, depth, results)) {
358            handleDirectoryStart(directory, depth, results);
359            final int childDepth = depth + 1;
360            if (depthLimit < 0 || childDepth <= depthLimit) {
361                checkIfCancelled(directory, depth, results);
362                File[] childFiles = filter == null ? directory.listFiles() : directory.listFiles(filter);
363                childFiles = filterDirectoryContents(directory, depth, childFiles);
364                if (childFiles == null) {
365                    handleRestricted(directory, childDepth, results);
366                } else {
367                    for (final File childFile : childFiles) {
368                        if (childFile.isDirectory()) {
369                            walk(childFile, childDepth, results);
370                        } else {
371                            checkIfCancelled(childFile, childDepth, results);
372                            handleFile(childFile, childDepth, results);
373                            checkIfCancelled(childFile, childDepth, results);
374                        }
375                    }
376                }
377            }
378            handleDirectoryEnd(directory, depth, results);
379        }
380        checkIfCancelled(directory, depth, results);
381    }
382
383    /**
384     * Checks whether the walk has been cancelled by calling {@link #handleIsCancelled},
385     * throwing a {@code CancelException} if it has.
386     * <p>
387     * Writers of subclasses should not normally call this method as it is called
388     * automatically by the walk of the tree. However, sometimes a single method,
389     * typically {@link #handleFile}, may take a long time to run. In that case,
390     * you may wish to check for cancellation by calling this method.
391     * </p>
392     *
393     * @param file  the current file being processed
394     * @param depth  the current file level (starting directory = 0)
395     * @param results  the collection of result objects, may be updated
396     * @throws IOException if an I/O Error occurs
397     */
398    protected final void checkIfCancelled(final File file, final int depth, final Collection<T> results) throws
399            IOException {
400        if (handleIsCancelled(file, depth, results)) {
401            throw new CancelException(file, depth);
402        }
403    }
404
405    /**
406     * Overridable callback method invoked to determine if the entire walk
407     * operation should be immediately cancelled.
408     * <p>
409     * This method should be implemented by those subclasses that want to
410     * provide a public {@code cancel()} method available from another
411     * thread. The design pattern for the subclass should be as follows:
412     * </p>
413     * <pre>
414     *  public class FooDirectoryWalker extends DirectoryWalker {
415     *    private volatile boolean cancelled = false;
416     *
417     *    public void cancel() {
418     *        cancelled = true;
419     *    }
420     *    private void handleIsCancelled(File file, int depth, Collection results) {
421     *        return cancelled;
422     *    }
423     *    protected void handleCancelled(File startDirectory,
424     *              Collection results, CancelException cancel) {
425     *        // implement processing required when a cancellation occurs
426     *    }
427     *  }
428     * </pre>
429     * <p>
430     * If this method returns true, then the directory walk is immediately
431     * cancelled. The next callback method will be {@link #handleCancelled}.
432     * </p>
433     * <p>
434     * This implementation returns false.
435     * </p>
436     *
437     * @param file  the file or directory being processed
438     * @param depth  the current directory level (starting directory = 0)
439     * @param results  the collection of result objects, may be updated
440     * @return true if the walk has been cancelled
441     * @throws IOException if an I/O Error occurs
442     */
443    @SuppressWarnings("unused") // Possibly thrown from subclasses.
444    protected boolean handleIsCancelled(
445            final File file, final int depth, final Collection<T> results) throws IOException {
446        // do nothing - overridable by subclass
447        return false;  // not cancelled
448    }
449
450    /**
451     * Overridable callback method invoked when the operation is cancelled.
452     * The file being processed when the cancellation occurred can be
453     * obtained from the exception.
454     * <p>
455     * This implementation just re-throws the {@link CancelException}.
456     * </p>
457     *
458     * @param startDirectory  the directory that the walk started from
459     * @param results  the collection of result objects, may be updated
460     * @param cancel  the exception throw to cancel further processing
461     * containing details at the point of cancellation.
462     * @throws IOException if an I/O Error occurs
463     */
464    protected void handleCancelled(final File startDirectory, final Collection<T> results,
465                       final CancelException cancel) throws IOException {
466        // re-throw exception - overridable by subclass
467        throw cancel;
468    }
469
470    /**
471     * Overridable callback method invoked at the start of processing.
472     * <p>
473     * This implementation does nothing.
474     * </p>
475     *
476     * @param startDirectory  the directory to start from
477     * @param results  the collection of result objects, may be updated
478     * @throws IOException if an I/O Error occurs
479     */
480    @SuppressWarnings("unused") // Possibly thrown from subclasses.
481    protected void handleStart(final File startDirectory, final Collection<T> results) throws IOException {
482        // do nothing - overridable by subclass
483    }
484
485    /**
486     * Overridable callback method invoked to determine if a directory should be processed.
487     * <p>
488     * This method returns a boolean to indicate if the directory should be examined or not.
489     * If you return false, the entire directory and any subdirectories will be skipped.
490     * Note that this functionality is in addition to the filtering by file filter.
491     * </p>
492     * <p>
493     * This implementation does nothing and returns true.
494     * </p>
495     *
496     * @param directory  the current directory being processed
497     * @param depth  the current directory level (starting directory = 0)
498     * @param results  the collection of result objects, may be updated
499     * @return true to process this directory, false to skip this directory
500     * @throws IOException if an I/O Error occurs
501     */
502    @SuppressWarnings("unused") // Possibly thrown from subclasses.
503    protected boolean handleDirectory(final File directory, final int depth, final Collection<T> results) throws
504            IOException {
505        // do nothing - overridable by subclass
506        return true;  // process directory
507    }
508
509    /**
510     * Overridable callback method invoked at the start of processing each directory.
511     * <p>
512     * This implementation does nothing.
513     * </p>
514     *
515     * @param directory  the current directory being processed
516     * @param depth  the current directory level (starting directory = 0)
517     * @param results  the collection of result objects, may be updated
518     * @throws IOException if an I/O Error occurs
519     */
520    @SuppressWarnings("unused") // Possibly thrown from subclasses.
521    protected void handleDirectoryStart(final File directory, final int depth, final Collection<T> results) throws
522            IOException {
523        // do nothing - overridable by subclass
524    }
525
526    /**
527     * Overridable callback method invoked with the contents of each directory.
528     * <p>
529     * This implementation returns the files unchanged
530     * </p>
531     *
532     * @param directory  the current directory being processed
533     * @param depth  the current directory level (starting directory = 0)
534     * @param files the files (possibly filtered) in the directory, may be {@code null}
535     * @return the filtered list of files
536     * @throws IOException if an I/O Error occurs
537     * @since 2.0
538     */
539    @SuppressWarnings("unused") // Possibly thrown from subclasses.
540    protected File[] filterDirectoryContents(final File directory, final int depth, final File... files) throws
541            IOException {
542        return files;
543    }
544
545    /**
546     * Overridable callback method invoked for each (non-directory) file.
547     * <p>
548     * This implementation does nothing.
549     * </p>
550     *
551     * @param file  the current file being processed
552     * @param depth  the current directory level (starting directory = 0)
553     * @param results  the collection of result objects, may be updated
554     * @throws IOException if an I/O Error occurs
555     */
556    @SuppressWarnings("unused") // Possibly thrown from subclasses.
557    protected void handleFile(final File file, final int depth, final Collection<T> results) throws IOException {
558        // do nothing - overridable by subclass
559    }
560
561    /**
562     * Overridable callback method invoked for each restricted directory.
563     * <p>
564     * This implementation does nothing.
565     * </p>
566     *
567     * @param directory  the restricted directory
568     * @param depth  the current directory level (starting directory = 0)
569     * @param results  the collection of result objects, may be updated
570     * @throws IOException if an I/O Error occurs
571     */
572    @SuppressWarnings("unused") // Possibly thrown from subclasses.
573    protected void handleRestricted(final File directory, final int depth, final Collection<T> results) throws
574            IOException {
575        // do nothing - overridable by subclass
576    }
577
578    /**
579     * Overridable callback method invoked at the end of processing each directory.
580     * <p>
581     * This implementation does nothing.
582     * </p>
583     *
584     * @param directory  the directory being processed
585     * @param depth  the current directory level (starting directory = 0)
586     * @param results  the collection of result objects, may be updated
587     * @throws IOException if an I/O Error occurs
588     */
589    @SuppressWarnings("unused") // Possibly thrown from subclasses.
590    protected void handleDirectoryEnd(final File directory, final int depth, final Collection<T> results) throws
591            IOException {
592        // do nothing - overridable by subclass
593    }
594
595    /**
596     * Overridable callback method invoked at the end of processing.
597     * <p>
598     * This implementation does nothing.
599     * </p>
600     *
601     * @param results  the collection of result objects, may be updated
602     * @throws IOException if an I/O Error occurs
603     */
604    @SuppressWarnings("unused") // Possibly thrown from subclasses.
605    protected void handleEnd(final Collection<T> results) throws IOException {
606        // do nothing - overridable by subclass
607    }
608
609    /**
610     * CancelException is thrown in DirectoryWalker to cancel the current
611     * processing.
612     */
613    public static class CancelException extends IOException {
614
615        /** Serialization id. */
616        private static final long serialVersionUID = 1347339620135041008L;
617
618        /** The file being processed when the exception was thrown. */
619        private final File file;
620        /** The file depth when the exception was thrown. */
621        private final int depth;
622
623        /**
624         * Constructs a {@code CancelException} with
625         * the file and depth when cancellation occurred.
626         *
627         * @param file  the file when the operation was cancelled, may be null
628         * @param depth  the depth when the operation was cancelled, may be null
629         */
630        public CancelException(final File file, final int depth) {
631            this("Operation Cancelled", file, depth);
632        }
633
634        /**
635         * Constructs a {@code CancelException} with
636         * an appropriate message and the file and depth when
637         * cancellation occurred.
638         *
639         * @param message  the detail message
640         * @param file  the file when the operation was cancelled
641         * @param depth  the depth when the operation was cancelled
642         */
643        public CancelException(final String message, final File file, final int depth) {
644            super(message);
645            this.file = file;
646            this.depth = depth;
647        }
648
649        /**
650         * Returns the file when the operation was cancelled.
651         *
652         * @return the file when the operation was cancelled
653         */
654        public File getFile() {
655            return file;
656        }
657
658        /**
659         * Returns the depth when the operation was cancelled.
660         *
661         * @return the depth when the operation was cancelled
662         */
663        public int getDepth() {
664            return depth;
665        }
666    }
667}