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: */
017: package org.apache.commons.io;
018:
019: import 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: * {@link javax.servlet.ServletContextListener#contextDestroyed} or similar.
034: *
035: * @author Noel Bergman
036: * @author Martin Cooper
037: * @version $Id: FileCleaner.java 551002 2007-06-27 01:33:05Z jochen $
038: */
039: public class FileCleaner {
040: /**
041: * The instance to use for the deprecated, static methods.
042: */
043: static final FileCleaningTracker theInstance = new FileCleaningTracker();
044:
045: //-----------------------------------------------------------------------
046: /**
047: * Track the specified file, using the provided marker, deleting the file
048: * when the marker instance is garbage collected.
049: * The {@link FileDeleteStrategy#NORMAL normal} deletion strategy will be used.
050: *
051: * @param file the file to be tracked, not null
052: * @param marker the marker object used to track the file, not null
053: * @throws NullPointerException if the file is null
054: */
055: public static void track(File file, Object marker) {
056: theInstance.track(file, marker);
057: }
058:
059: /**
060: * Track the specified file, using the provided marker, deleting the file
061: * when the marker instance is garbage collected.
062: * The speified deletion strategy is used.
063: *
064: * @param file the file to be tracked, not null
065: * @param marker the marker object used to track the file, not null
066: * @param deleteStrategy the strategy to delete the file, null means normal
067: * @throws NullPointerException if the file is null
068: */
069: public static void track(File file, Object marker,
070: FileDeleteStrategy deleteStrategy) {
071: theInstance.track(file, marker, deleteStrategy);
072: }
073:
074: /**
075: * Track the specified file, using the provided marker, deleting the file
076: * when the marker instance is garbage collected.
077: * The {@link FileDeleteStrategy#NORMAL normal} deletion strategy will be used.
078: *
079: * @param path the full path to the file to be tracked, not null
080: * @param marker the marker object used to track the file, not null
081: * @throws NullPointerException if the path is null
082: */
083: public static void track(String path, Object marker) {
084: theInstance.track(path, marker);
085: }
086:
087: /**
088: * Track the specified file, using the provided marker, deleting the file
089: * when the marker instance is garbage collected.
090: * The speified deletion strategy is used.
091: *
092: * @param path the full path to the file to be tracked, not null
093: * @param marker the marker object used to track the file, not null
094: * @param deleteStrategy the strategy to delete the file, null means normal
095: * @throws NullPointerException if the path is null
096: */
097: public static void track(String path, Object marker,
098: FileDeleteStrategy deleteStrategy) {
099: theInstance.track(path, marker, deleteStrategy);
100: }
101:
102: //-----------------------------------------------------------------------
103: /**
104: * Retrieve the number of files currently being tracked, and therefore
105: * awaiting deletion.
106: *
107: * @return the number of files being tracked
108: */
109: public static int getTrackCount() {
110: return theInstance.getTrackCount();
111: }
112:
113: /**
114: * Call this method to cause the file cleaner thread to terminate when
115: * there are no more objects being tracked for deletion.
116: * <p>
117: * In a simple environment, you don't need this method as the file cleaner
118: * thread will simply exit when the JVM exits. In a more complex environment,
119: * with multiple class loaders (such as an application server), you should be
120: * aware that the file cleaner thread will continue running even if the class
121: * loader it was started from terminates. This can consitute a memory leak.
122: * <p>
123: * For example, suppose that you have developed a web application, which
124: * contains the commons-io jar file in your WEB-INF/lib directory. In other
125: * words, the FileCleaner class is loaded through the class loader of your
126: * web application. If the web application is terminated, but the servlet
127: * container is still running, then the file cleaner thread will still exist,
128: * posing a memory leak.
129: * <p>
130: * This method allows the thread to be terminated. Simply call this method
131: * in the resource cleanup code, such as {@link javax.servlet.ServletContextListener#contextDestroyed}.
132: * One called, no new objects can be tracked by the file cleaner.
133: */
134: public static synchronized void exitWhenFinished() {
135: theInstance.exitWhenFinished();
136: }
137:
138: /**
139: * Returns the singleton instance, which is used by the deprecated, static methods.
140: * This is mainly useful for code, which wants to support the new
141: * {@link FileCleaningTracker} class while maintain compatibility with the
142: * deprecated {@link FileCleaner}.
143: */
144: public static FileCleaningTracker getInstance() {
145: return theInstance;
146: }
147: }
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