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.IOException;
021
022/**
023 * Strategy for deleting files.
024 * <p>
025 * There is more than one way to delete a file.
026 * You may want to limit access to certain directories, to only delete
027 * directories if they are empty, or maybe to force deletion.
028 * </p>
029 * <p>
030 * This class captures the strategy to use and is designed for user subclassing.
031 * </p>
032 *
033 * @since 1.3
034 */
035public class FileDeleteStrategy {
036
037    /**
038     * Force file deletion strategy.
039     */
040    static class ForceFileDeleteStrategy extends FileDeleteStrategy {
041        /** Default Constructor */
042        ForceFileDeleteStrategy() {
043            super("Force");
044        }
045
046        /**
047         * Deletes the file object.
048         * <p>
049         * This implementation uses <code>FileUtils.forceDelete()</code>
050         * if the file exists.
051         * </p>
052         *
053         * @param fileToDelete  the file to delete, not null
054         * @return Always returns {@code true}
055         * @throws NullPointerException if the file is null
056         * @throws IOException if an error occurs during file deletion
057         */
058        @Override
059        protected boolean doDelete(final File fileToDelete) throws IOException {
060            FileUtils.forceDelete(fileToDelete);
061            return true;
062        }
063    }
064
065    /**
066     * The singleton instance for normal file deletion, which does not permit
067     * the deletion of directories that are not empty.
068     */
069    public static final FileDeleteStrategy NORMAL = new FileDeleteStrategy("Normal");
070
071    /**
072     * The singleton instance for forced file deletion, which always deletes,
073     * even if the file represents a non-empty directory.
074     */
075    public static final FileDeleteStrategy FORCE = new ForceFileDeleteStrategy();
076
077    /** The name of the strategy. */
078    private final String name;
079
080    /**
081     * Restricted constructor.
082     *
083     * @param name  the name by which the strategy is known
084     */
085    protected FileDeleteStrategy(final String name) {
086        this.name = name;
087    }
088
089    /**
090     * Deletes the file object, which may be a file or a directory.
091     * If the file does not exist, the method just returns.
092     * <p>
093     * Subclass writers should override {@link #doDelete(File)}, not this method.
094     * </p>
095     *
096     * @param fileToDelete  the file to delete, not null
097     * @throws NullPointerException if the file is null
098     * @throws IOException if an error occurs during file deletion
099     */
100    public void delete(final File fileToDelete) throws IOException {
101        if (fileToDelete.exists() && doDelete(fileToDelete) == false) {
102            throw new IOException("Deletion failed: " + fileToDelete);
103        }
104    }
105
106    /**
107     * Deletes the file object, which may be a file or a directory.
108     * All <code>IOException</code>s are caught and false returned instead.
109     * If the file does not exist or is null, true is returned.
110     * <p>
111     * Subclass writers should override {@link #doDelete(File)}, not this method.
112     * </p>
113     *
114     * @param fileToDelete  the file to delete, null returns true
115     * @return true if the file was deleted, or there was no such file
116     */
117    public boolean deleteQuietly(final File fileToDelete) {
118        if (fileToDelete == null || fileToDelete.exists() == false) {
119            return true;
120        }
121        try {
122            return doDelete(fileToDelete);
123        } catch (final IOException ex) {
124            return false;
125        }
126    }
127
128    /**
129     * Actually deletes the file object, which may be a file or a directory.
130     * <p>
131     * This method is designed for subclasses to override.
132     * The implementation may return either false or an <code>IOException</code>
133     * when deletion fails. The {@link #delete(File)} and {@link #deleteQuietly(File)}
134     * methods will handle either response appropriately.
135     * A check has been made to ensure that the file will exist.
136     * </p>
137     * <p>
138     * This implementation uses {@link File#delete()}.
139     * </p>
140     *
141     * @param fileToDelete  the file to delete, exists, not null
142     * @return true if the file was deleted
143     * @throws NullPointerException if the file is null
144     * @throws IOException if an error occurs during file deletion
145     */
146    protected boolean doDelete(final File fileToDelete) throws IOException {
147        return fileToDelete.delete();
148    }
149
150    /**
151     * Gets a string describing the delete strategy.
152     *
153     * @return a string describing the delete strategy
154     */
155    @Override
156    public String toString() {
157        return "FileDeleteStrategy[" + name + "]";
158    }
159
160}