KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > apache > commons > io > FileCleaner


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.io;
17
18 import java.io.File JavaDoc;
19 import java.lang.ref.PhantomReference JavaDoc;
20 import java.lang.ref.ReferenceQueue JavaDoc;
21 import java.util.Collection JavaDoc;
22 import java.util.Vector JavaDoc;
23
24 /**
25  * Keeps track of files awaiting deletion, and deletes them when an associated
26  * marker object is reclaimed by the garbage collector.
27  *
28  * @author Noel Bergman
29  * @author Martin Cooper
30  *
31  * @version $Id: FileCleaner.java,v 1.1 2004/03/18 06:04:14 martinc Exp $
32  */
33 public class FileCleaner {
34
35     /**
36      * Queue of <code>Tracker</code> instances being watched.
37      */
38     private static ReferenceQueue JavaDoc /* Tracker */ q = new ReferenceQueue JavaDoc();
39
40     /**
41      * Collection of <code>Tracker</code> instances in existence.
42      */
43     private static Collection JavaDoc /* Tracker */ trackers = new Vector JavaDoc();
44
45     /**
46      * The thread that will clean up registered files.
47      */
48     private static Thread JavaDoc reaper = new Thread JavaDoc("File Reaper") {
49
50         /**
51          * Run the reaper thread that will delete files as their associated
52          * marker objects are reclaimed by the garbage collector.
53          */
54         public void run() {
55             for (;;) {
56                 Tracker tracker = null;
57                 try {
58                     // Wait for a tracker to remove.
59 tracker = (Tracker) q.remove();
60                 } catch(Exception JavaDoc _) {
61                     continue;
62                 }
63
64                 tracker.delete();
65                 tracker.clear();
66                 trackers.remove(tracker);
67             }
68         }
69     };
70
71     /**
72      * The static initializer that starts the reaper thread.
73      */
74     static {
75         reaper.setPriority(Thread.MAX_PRIORITY);
76         reaper.setDaemon(true);
77         reaper.start();
78     }
79
80     /**
81      * Track the specified file, using the provided marker, deleting the file
82      * when the marker instance is garbage collected.
83      *
84      * @param file The file to be tracked.
85      * @param marker The marker object used to track the file.
86      */
87     public static void track(File JavaDoc file, Object JavaDoc marker) {
88         trackers.add(new Tracker(file, marker, q));
89     }
90
91     /**
92      * Track the specified file, using the provided marker, deleting the file
93      * when the marker instance is garbage collected.
94      *
95      * @param path The full path to the file to be tracked.
96      * @param marker The marker object used to track the file.
97      */
98     public static void track(String JavaDoc path, Object JavaDoc marker) {
99         trackers.add(new Tracker(path, marker, q));
100     }
101
102     /**
103      * Retrieve the number of files currently being tracked, and therefore
104      * awaiting deletion.
105      *
106      * @return the number of files being tracked.
107      */
108     public static int getTrackCount() {
109         return trackers.size();
110     }
111
112     /**
113      * Inner class which acts as the reference for a file pending deletion.
114      */
115     private static class Tracker extends PhantomReference JavaDoc {
116
117         /**
118          * The full path to the file being tracked.
119          */
120         private String JavaDoc path;
121
122         /**
123          * Constructs an instance of this class from the supplied parameters.
124          *
125          * @param file The file to be tracked.
126          * @param marker The marker object used to track the file.
127          * @param q The queue on to which the tracker will be pushed.
128          */
129         public Tracker(File JavaDoc file, Object JavaDoc marker, ReferenceQueue JavaDoc q) {
130             this(file.getPath(), marker, q);
131         }
132
133         /**
134          * Constructs an instance of this class from the supplied parameters.
135          *
136          * @param path The full path to the file to be tracked.
137          * @param marker The marker object used to track the file.
138          * @param q The queue on to which the tracker will be pushed.
139          */
140         public Tracker(String JavaDoc path, Object JavaDoc marker, ReferenceQueue JavaDoc q) {
141             super(marker, q);
142             this.path = path;
143         }
144
145         /**
146          * Deletes the file associated with this tracker instance.
147          *
148          * @return <code>true</code> if the file was deleted successfully;
149          * <code>false</code> otherwise.
150          */
151         public boolean delete() {
152             return new File JavaDoc(path).delete();
153         }
154     }
155 }
Popular Tags