1 package org.apache.turbine.services.cache;
2
3 /* ====================================================================
4 * The Apache Software License, Version 1.1
5 *
6 * Copyright (c) 2001 The Apache Software Foundation. All rights
7 * reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 *
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in
18 * the documentation and/or other materials provided with the
19 * distribution.
20 *
21 * 3. The end-user documentation included with the redistribution,
22 * if any, must include the following acknowledgment:
23 * "This product includes software developed by the
24 * Apache Software Foundation (http://www.apache.org/)."
25 * Alternately, this acknowledgment may appear in the software itself,
26 * if and wherever such third-party acknowledgments normally appear.
27 *
28 * 4. The names "Apache" and "Apache Software Foundation" and
29 * "Apache Turbine" must not be used to endorse or promote products
30 * derived from this software without prior written permission. For
31 * written permission, please contact apache@apache.org.
32 *
33 * 5. Products derived from this software may not be called "Apache",
34 * "Apache Turbine", nor may "Apache" appear in their name, without
35 * prior written permission of the Apache Software Foundation.
36 *
37 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
43 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
44 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
45 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48 * SUCH DAMAGE.
49 * ====================================================================
50 *
51 * This software consists of voluntary contributions made by many
52 * individuals on behalf of the Apache Software Foundation. For more
53 * information on the Apache Software Foundation, please see
54 * <http://www.apache.org/>.
55 */
56
57 /***
58 * The idea of the RefreshableCachedObject is that, rather than
59 * removing items from the cache when they become stale, we'll tell them to
60 * refresh themselves instead. That way they'll always be in the
61 * cache, and the code to refresh them will be run by the background
62 * thread rather than by a user request thread. You can also set a TTL (Time
63 * To Live) for the object. This way, if the object hasn't been touched
64 * for the TTL period, then it will be removed from the cache.
65 *
66 * This extends CachedObject and provides a method for refreshing the
67 * cached object, and resetting its expire time.
68 *
69 * @author <a href="mailto:nissim@nksystems.com">Nissim Karpenstein</a>
70 * @version $Id: RefreshableCachedObject.java,v 1.2 2002/01/30 16:11:21 dlr Exp $
71 */
72 public class RefreshableCachedObject
73 extends CachedObject
74 {
75
76 /***
77 * How long to wait before removing an untouched object from the cache.
78 * Negative numbers mean never remove (the default).
79 */
80 private long timeToLive = -1;
81
82 /***
83 * The last time the Object was accessed from the cache.
84 */
85 private long lastAccess;
86
87 /***
88 * Constructor; sets the object to expire in the default time (30
89 * minutes).
90 *
91 * @param o The object you want to cache.
92 */
93 public RefreshableCachedObject(Refreshable o)
94 {
95 super(o);
96 lastAccess = System.currentTimeMillis();
97 }
98
99 /***
100 * Constructor.
101 *
102 * @param o The object to cache.
103 * @param expires How long before the object expires, in ms,
104 * e.g. 1000 = 1 second.
105 */
106 public RefreshableCachedObject(Refreshable o,
107 long expires)
108 {
109 super(o, expires);
110 lastAccess = System.currentTimeMillis();
111 }
112
113 /*** sets the timeToLive member (in milliseconds) */
114 public synchronized void setTTL(long l) { timeToLive = l; }
115
116 /*** gets the timeToLive member (in milliseconds) */
117 public synchronized long getTTL() { return timeToLive; }
118
119 /***
120 * Sets the last acccess time to the current time.
121 */
122 public synchronized void touch()
123 {
124 lastAccess = System.currentTimeMillis();
125 }
126
127 /***
128 * Returns true if the object hasn't been touched
129 * in the previous TTL period.
130 */
131 public synchronized boolean isUntouched()
132 {
133 if (timeToLive < 0)
134 return false;
135
136 if (lastAccess + timeToLive < System.currentTimeMillis())
137 return true;
138 else
139 return false;
140 }
141
142 /***
143 * Refresh the object and the created time.
144 */
145 public void refresh()
146 {
147 Refreshable r = (Refreshable)getContents();
148 synchronized (this)
149 {
150 created = System.currentTimeMillis();
151 r.refresh();
152 }
153 }
154 }
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