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org.apache.turbine.services.cache.RefreshableCachedObject |
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1 | package org.apache.turbine.services.cache; |
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2 | ||
3 | /* |
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4 | * Copyright 2001-2005 The Apache Software Foundation. |
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5 | * |
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6 | * Licensed under the Apache License, Version 2.0 (the "License") |
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7 | * you may not use this file except in compliance with the License. |
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8 | * You may obtain a copy of the License at |
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9 | * |
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10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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11 | * |
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12 | * Unless required by applicable law or agreed to in writing, software |
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13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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15 | * See the License for the specific language governing permissions and |
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16 | * limitations under the License. |
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17 | */ |
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18 | ||
19 | /** |
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20 | * The idea of the RefreshableCachedObject is that, rather than |
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21 | * removing items from the cache when they become stale, we'll tell them to |
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22 | * refresh themselves instead. That way they'll always be in the |
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23 | * cache, and the code to refresh them will be run by the background |
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24 | * thread rather than by a user request thread. You can also set a TTL (Time |
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25 | * To Live) for the object. This way, if the object hasn't been touched |
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26 | * for the TTL period, then it will be removed from the cache. |
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27 | * |
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28 | * This extends CachedObject and provides a method for refreshing the |
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29 | * cached object, and resetting its expire time. |
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30 | * |
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31 | * @author <a href="mailto:nissim@nksystems.com">Nissim Karpenstein</a> |
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32 | * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a> |
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33 | * @version $Id: RefreshableCachedObject.java 278822 2005-09-05 19:53:05Z henning $ |
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34 | */ |
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35 | public class RefreshableCachedObject |
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36 | extends CachedObject |
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37 | { |
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38 | ||
39 | /** Serial Version UID */ |
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40 | private static final long serialVersionUID = 727229797378897180L; |
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41 | ||
42 | /** |
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43 | * How long to wait before removing an untouched object from the cache. |
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44 | * Negative numbers mean never remove (the default). |
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45 | */ |
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46 | 0 | private long timeToLive = -1; |
47 | ||
48 | /** |
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49 | * The last time the Object was accessed from the cache. |
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50 | */ |
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51 | private long lastAccess; |
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52 | ||
53 | /** |
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54 | * Constructor; sets the object to expire in the default time (30 |
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55 | * minutes). |
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56 | * |
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57 | * @param o The object you want to cache. |
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58 | */ |
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59 | public RefreshableCachedObject(Refreshable o) |
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60 | { |
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61 | 0 | super(o); |
62 | 0 | lastAccess = System.currentTimeMillis(); |
63 | 0 | } |
64 | ||
65 | /** |
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66 | * Constructor. |
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67 | * |
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68 | * @param o The object to cache. |
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69 | * @param expires How long before the object expires, in ms, |
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70 | * e.g. 1000 = 1 second. |
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71 | */ |
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72 | public RefreshableCachedObject(Refreshable o, |
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73 | long expires) |
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74 | { |
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75 | 0 | super(o, expires); |
76 | 0 | lastAccess = System.currentTimeMillis(); |
77 | 0 | } |
78 | ||
79 | /** |
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80 | * Sets the timeToLive value |
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81 | * |
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82 | * @param timeToLive the new Value in milliseconds |
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83 | */ |
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84 | public synchronized void setTTL(long timeToLive) |
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85 | { |
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86 | 0 | this.timeToLive = timeToLive; |
87 | 0 | } |
88 | ||
89 | /** |
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90 | * Gets the timeToLive value. |
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91 | * |
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92 | * @return The current timeToLive value (in milliseconds) |
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93 | */ |
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94 | public synchronized long getTTL() |
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95 | { |
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96 | 0 | return timeToLive; |
97 | } |
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98 | ||
99 | /** |
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100 | * Sets the last acccess time to the current time. |
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101 | */ |
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102 | public synchronized void touch() |
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103 | { |
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104 | 0 | lastAccess = System.currentTimeMillis(); |
105 | 0 | } |
106 | ||
107 | /** |
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108 | * Returns true if the object hasn't been touched |
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109 | * in the previous TTL period. |
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110 | */ |
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111 | public synchronized boolean isUntouched() |
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112 | { |
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113 | 0 | if (timeToLive < 0) |
114 | 0 | return false; |
115 | ||
116 | 0 | if (lastAccess + timeToLive < System.currentTimeMillis()) |
117 | 0 | return true; |
118 | else |
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119 | 0 | return false; |
120 | } |
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121 | ||
122 | /** |
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123 | * Refresh the object and the created time. |
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124 | */ |
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125 | public void refresh() |
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126 | { |
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127 | 0 | Refreshable r = (Refreshable) getContents(); |
128 | 0 | synchronized (this) |
129 | { |
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130 | 0 | created = System.currentTimeMillis(); |
131 | 0 | r.refresh(); |
132 | 0 | } |
133 | 0 | } |
134 | } |
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