    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 *      https://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;
    020
    021/**
    022 * Keeps track of files awaiting deletion, and deletes them when an associated
    023 * marker object is reclaimed by the garbage collector.
    024 * <p>
    025 * This utility creates a background thread to handle file deletion.
    026 * Each file to be deleted is registered with a handler object.
    027 * When the handler object is garbage collected, the file is deleted.
    028 * <p>
    029 * In an environment with multiple class loaders (a servlet container, for
    030 * example), you should consider stopping the background thread if it is no
    031 * longer needed. This is done by invoking the method
    032 * {@link #exitWhenFinished}, typically in
    033 * {@code javax.servlet.ServletContextListener.contextDestroyed(javax.servlet.ServletContextEvent)} or similar.
    034 *
    035 * @deprecated Use {@link FileCleaningTracker}
    036 */
    037@Deprecated
    038public class FileCleaner {
    039
    040    /**
    041     * The instance to use for the deprecated, static methods.
    042     */
    043    private static final FileCleaningTracker INSTANCE = new FileCleaningTracker();
    044
    045    /**
    046     * Call this method to cause the file cleaner thread to terminate when
    047     * there are no more objects being tracked for deletion.
    048     * <p>
    049     * In a simple environment, you don't need this method as the file cleaner
    050     * thread will simply exit when the JVM exits. In a more complex environment,
    051     * with multiple class loaders (such as an application server), you should be
    052     * aware that the file cleaner thread will continue running even if the class
    053     * loader it was started from terminates. This can constitute a memory leak.
    054     * <p>
    055     * For example, suppose that you have developed a web application, which
    056     * contains the Commons IO jar file in your WEB-INF/lib directory. In other
    057     * words, the FileCleaner class is loaded through the class loader of your
    058     * web application. If the web application is terminated, but the servlet
    059     * container is still running, then the file cleaner thread will still exist,
    060     * posing a memory leak.
    061     * <p>
    062     * This method allows the thread to be terminated. Simply call this method
    063     * in the resource cleanup code, such as
    064     * {@code javax.servlet.ServletContextListener.contextDestroyed(javax.servlet.ServletContextEvent)}.
    065     * One called, no new objects can be tracked by the file cleaner.
    066     *
    067     * @deprecated Use {@link FileCleaningTracker#exitWhenFinished()}.
    068     */
    069    @Deprecated
    070    public static synchronized void exitWhenFinished() {
    071        INSTANCE.exitWhenFinished();
    072    }
    073
    074    /**
    075     * Gets the singleton instance, which is used by the deprecated, static methods.
    076     * This is mainly useful for code, which wants to support the new
    077     * {@link FileCleaningTracker} class while maintain compatibility with the
    078     * deprecated {@link FileCleaner}.
    079     *
    080     * @return the singleton instance.
    081     */
    082    public static FileCleaningTracker getInstance() {
    083        return INSTANCE;
    084    }
    085
    086    /**
    087     * Gets the number of files currently being tracked, and therefore
    088     * awaiting deletion.
    089     *
    090     * @return the number of files being tracked.
    091     * @deprecated Use {@link FileCleaningTracker#getTrackCount()}.
    092     */
    093    @Deprecated
    094    public static int getTrackCount() {
    095        return INSTANCE.getTrackCount();
    096    }
    097
    098    /**
    099     * Track the specified file, using the provided marker, deleting the file
    100     * when the marker instance is garbage collected.
    101     * The {@link FileDeleteStrategy#NORMAL normal} deletion strategy will be used.
    102     *
    103     * @param file  the file to be tracked, not null.
    104     * @param marker  the marker object used to track the file, not null.
    105     * @throws NullPointerException if the file is null.
    106     * @deprecated Use {@link FileCleaningTracker#track(File, Object)}.
    107     */
    108    @Deprecated
    109    public static void track(final File file, final Object marker) {
    110        INSTANCE.track(file, marker);
    111    }
    112
    113    /**
    114     * Track the specified file, using the provided marker, deleting the file
    115     * when the marker instance is garbage collected.
    116     * The specified deletion strategy is used.
    117     *
    118     * @param file  the file to be tracked, not null.
    119     * @param marker  the marker object used to track the file, not null.
    120     * @param deleteStrategy  the strategy to delete the file, null means normal.
    121     * @throws NullPointerException if the file is null.
    122     * @deprecated Use {@link FileCleaningTracker#track(File, Object, FileDeleteStrategy)}.
    123     */
    124    @Deprecated
    125    public static void track(final File file, final Object marker, final FileDeleteStrategy deleteStrategy) {
    126        INSTANCE.track(file, marker, deleteStrategy);
    127    }
    128
    129    /**
    130     * Track the specified file, using the provided marker, deleting the file
    131     * when the marker instance is garbage collected.
    132     * The {@link FileDeleteStrategy#NORMAL normal} deletion strategy will be used.
    133     *
    134     * @param path  the full path to the file to be tracked, not null.
    135     * @param marker  the marker object used to track the file, not null.
    136     * @throws NullPointerException if the path is null.
    137     * @deprecated Use {@link FileCleaningTracker#track(String, Object)}.
    138     */
    139    @Deprecated
    140    public static void track(final String path, final Object marker) {
    141        INSTANCE.track(path, marker);
    142    }
    143
    144    /**
    145     * Track the specified file, using the provided marker, deleting the file
    146     * when the marker instance is garbage collected.
    147     * The specified deletion strategy is used.
    148     *
    149     * @param path  the full path to the file to be tracked, not null.
    150     * @param marker  the marker object used to track the file, not null.
    151     * @param deleteStrategy  the strategy to delete the file, null means normal.
    152     * @throws NullPointerException if the path is null.
    153     * @deprecated Use {@link FileCleaningTracker#track(String, Object, FileDeleteStrategy)}.
    154     */
    155    @Deprecated
    156    public static void track(final String path, final Object marker, final FileDeleteStrategy deleteStrategy) {
    157        INSTANCE.track(path, marker, deleteStrategy);
    158    }
    159
    160    /**
    161     * Construct a new instance.
    162     */
    163    public FileCleaner() {
    164        // empty
    165    }
    166}