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
042        /** Default Constructor */
043        ForceFileDeleteStrategy() {
044            super("Force");
045        }
046
047        /**
048         * Deletes the file object.
049         * <p>
050         * This implementation uses {@code FileUtils.forceDelete()}
051         * if the file exists.
052         * </p>
053         *
054         * @param fileToDelete  the file to delete, not null
055         * @return Always returns {@code true}
056         * @throws NullPointerException if the file is null
057         * @throws IOException if an error occurs during file deletion
058         */
059        @Override
060        protected boolean doDelete(final File fileToDelete) throws IOException {
061            FileUtils.forceDelete(fileToDelete);
062            return true;
063        }
064    }
065
066    /**
067     * The singleton instance for normal file deletion, which does not permit
068     * the deletion of directories that are not empty.
069     */
070    public static final FileDeleteStrategy NORMAL = new FileDeleteStrategy("Normal");
071
072    /**
073     * The singleton instance for forced file deletion, which always deletes,
074     * even if the file represents a non-empty directory.
075     */
076    public static final FileDeleteStrategy FORCE = new ForceFileDeleteStrategy();
077
078    /** The name of the strategy. */
079    private final String name;
080
081    /**
082     * Restricted constructor.
083     *
084     * @param name  the name by which the strategy is known
085     */
086    protected FileDeleteStrategy(final String name) {
087        this.name = name;
088    }
089
090    /**
091     * Deletes the file object, which may be a file or a directory.
092     * If the file does not exist, the method just returns.
093     * <p>
094     * Subclass writers should override {@link #doDelete(File)}, not this method.
095     * </p>
096     *
097     * @param fileToDelete  the file to delete, not null
098     * @throws NullPointerException if the file is null
099     * @throws IOException if an error occurs during file deletion
100     */
101    public void delete(final File fileToDelete) throws IOException {
102        if (fileToDelete.exists() && !doDelete(fileToDelete)) {
103            throw new IOException("Deletion failed: " + fileToDelete);
104        }
105    }
106
107    /**
108     * Deletes the file object, which may be a file or a directory.
109     * All {@link IOException}s are caught and false returned instead.
110     * If the file does not exist or is null, true is returned.
111     * <p>
112     * Subclass writers should override {@link #doDelete(File)}, not this method.
113     * </p>
114     *
115     * @param fileToDelete  the file to delete, null returns true
116     * @return true if the file was deleted, or there was no such file
117     */
118    public boolean deleteQuietly(final File fileToDelete) {
119        if (fileToDelete == null || !fileToDelete.exists()) {
120            return true;
121        }
122        try {
123            return doDelete(fileToDelete);
124        } catch (final IOException ex) {
125            return false;
126        }
127    }
128
129    /**
130     * Actually deletes the file object, which may be a file or a directory.
131     * <p>
132     * This method is designed for subclasses to override.
133     * The implementation may return either false or an {@link IOException}
134     * when deletion fails. The {@link #delete(File)} and {@link #deleteQuietly(File)}
135     * methods will handle either response appropriately.
136     * A check has been made to ensure that the file will exist.
137     * </p>
138     * <p>
139     * This implementation uses {@link FileUtils#delete(File)}.
140     * </p>
141     *
142     * @param file  the file to delete, exists, not null
143     * @return true if the file was deleted
144     * @throws NullPointerException if the file is null
145     * @throws IOException if an error occurs during file deletion
146     */
147    protected boolean doDelete(final File file) throws IOException {
148        FileUtils.delete(file);
149        return true;
150    }
151
152    /**
153     * Gets a string describing the delete strategy.
154     *
155     * @return a string describing the delete strategy
156     */
157    @Override
158    public String toString() {
159        return "FileDeleteStrategy[" + name + "]";
160    }
161
162}