1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.io;
18
19 import java.io.File;
20
21 /**
22 * Keeps track of files awaiting deletion, and deletes them when an associated
23 * marker object is reclaimed by the garbage collector.
24 * <p>
25 * This utility creates a background thread to handle file deletion.
26 * Each file to be deleted is registered with a handler object.
27 * When the handler object is garbage collected, the file is deleted.
28 * <p>
29 * In an environment with multiple class loaders (a servlet container, for
30 * example), you should consider stopping the background thread if it is no
31 * longer needed. This is done by invoking the method
32 * {@link #exitWhenFinished}, typically in
33 * {@link javax.servlet.ServletContextListener#contextDestroyed} or similar.
34 *
35 * @author Noel Bergman
36 * @author Martin Cooper
37 * @version $Id: FileCleaner.java 551002 2007-06-27 01:33:05Z jochen $
38 */
39 public class FileCleaner {
40 /**
41 * The instance to use for the deprecated, static methods.
42 */
43 static final FileCleaningTracker theInstance = new FileCleaningTracker();
44
45 //-----------------------------------------------------------------------
46 /**
47 * Track the specified file, using the provided marker, deleting the file
48 * when the marker instance is garbage collected.
49 * The {@link FileDeleteStrategy#NORMAL normal} deletion strategy will be used.
50 *
51 * @param file the file to be tracked, not null
52 * @param marker the marker object used to track the file, not null
53 * @throws NullPointerException if the file is null
54 */
55 public static void track(File file, Object marker) {
56 theInstance.track(file, marker);
57 }
58
59 /**
60 * Track the specified file, using the provided marker, deleting the file
61 * when the marker instance is garbage collected.
62 * The speified deletion strategy is used.
63 *
64 * @param file the file to be tracked, not null
65 * @param marker the marker object used to track the file, not null
66 * @param deleteStrategy the strategy to delete the file, null means normal
67 * @throws NullPointerException if the file is null
68 */
69 public static void track(File file, Object marker, FileDeleteStrategy deleteStrategy) {
70 theInstance.track(file, marker, deleteStrategy);
71 }
72
73 /**
74 * Track the specified file, using the provided marker, deleting the file
75 * when the marker instance is garbage collected.
76 * The {@link FileDeleteStrategy#NORMAL normal} deletion strategy will be used.
77 *
78 * @param path the full path to the file to be tracked, not null
79 * @param marker the marker object used to track the file, not null
80 * @throws NullPointerException if the path is null
81 */
82 public static void track(String path, Object marker) {
83 theInstance.track(path, marker);
84 }
85
86 /**
87 * Track the specified file, using the provided marker, deleting the file
88 * when the marker instance is garbage collected.
89 * The speified deletion strategy is used.
90 *
91 * @param path the full path to the file to be tracked, not null
92 * @param marker the marker object used to track the file, not null
93 * @param deleteStrategy the strategy to delete the file, null means normal
94 * @throws NullPointerException if the path is null
95 */
96 public static void track(String path, Object marker, FileDeleteStrategy deleteStrategy) {
97 theInstance.track(path, marker, deleteStrategy);
98 }
99
100 //-----------------------------------------------------------------------
101 /**
102 * Retrieve the number of files currently being tracked, and therefore
103 * awaiting deletion.
104 *
105 * @return the number of files being tracked
106 */
107 public static int getTrackCount() {
108 return theInstance.getTrackCount();
109 }
110
111 /**
112 * Call this method to cause the file cleaner thread to terminate when
113 * there are no more objects being tracked for deletion.
114 * <p>
115 * In a simple environment, you don't need this method as the file cleaner
116 * thread will simply exit when the JVM exits. In a more complex environment,
117 * with multiple class loaders (such as an application server), you should be
118 * aware that the file cleaner thread will continue running even if the class
119 * loader it was started from terminates. This can consitute a memory leak.
120 * <p>
121 * For example, suppose that you have developed a web application, which
122 * contains the commons-io jar file in your WEB-INF/lib directory. In other
123 * words, the FileCleaner class is loaded through the class loader of your
124 * web application. If the web application is terminated, but the servlet
125 * container is still running, then the file cleaner thread will still exist,
126 * posing a memory leak.
127 * <p>
128 * This method allows the thread to be terminated. Simply call this method
129 * in the resource cleanup code, such as {@link javax.servlet.ServletContextListener#contextDestroyed}.
130 * One called, no new objects can be tracked by the file cleaner.
131 */
132 public static synchronized void exitWhenFinished() {
133 theInstance.exitWhenFinished();
134 }
135
136 /**
137 * Returns the singleton instance, which is used by the deprecated, static methods.
138 * This is mainly useful for code, which wants to support the new
139 * {@link FileCleaningTracker} class while maintain compatibility with the
140 * deprecated {@link FileCleaner}.
141 */
142 public static FileCleaningTracker getInstance() {
143 return theInstance;
144 }
145 }