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Java > Open Source Codes > com > jcorporate > expresso > core > cache > CacheEntry


1 /* ====================================================================
2  * The Jcorporate Apache Style Software License, Version 1.2 05-07-2002
3  *
4  * Copyright (c) 1995-2002 Jcorporate Ltd. All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
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14  * notice, this list of conditions and the following disclaimer in
15  * the documentation and/or other materials provided with the
16  * distribution.
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18  * 3. The end-user documentation included with the redistribution,
19  * if any, must include the following acknowledgment:
20  * "This product includes software developed by Jcorporate Ltd.
21  * (http://www.jcorporate.com/)."
22  * Alternately, this acknowledgment may appear in the software itself,
23  * if and wherever such third-party acknowledgments normally appear.
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25  * 4. "Jcorporate" and product names such as "Expresso" must
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28  * please contact info@jcorporate.com.
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30  * 5. Products derived from this software may not be called "Expresso",
31  * or other Jcorporate product names; nor may "Expresso" or other
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54  * This software consists of voluntary contributions made by many
55  * individuals on behalf of the Jcorporate Ltd. Contributions back
56  * to the project(s) are encouraged when you make modifications.
57  * Please send them to support@jcorporate.com. For more information
58  * on Jcorporate Ltd. and its products, please see
59  * <http://www.jcorporate.com/>.
60  *
61  * Portions of this software are based upon other open source
62  * products and are subject to their respective licenses.
63  */
64
65 package com.jcorporate.expresso.core.cache;
66
67 /**
68  * Wrapper for any Cacheable object to be stored in a cache.
69  * This wrapper provides some utility services
70  * to the cacheable object, like maintaining it's usage count
71  * (for the least-frequently-used algorithm
72  * used to free up cache space when needed) and the expiry time
73  * of the object (for caches that use
74  * timed expiry of objects - e.g. keep it cached for x seconds)
75  */
76 public final class CacheEntry {
77
78     /**
79      * the object to be cached
80      */
81     private Cacheable contents = null;
82
83     /**
84      * When created *
85      */
86     protected long created = 0;
87
88     /**
89      * When it expires - default is never to expire *
90      */
91     private long expires = -1;
92     private long useCount = 0;
93
94     /**
95      * Constructor 1
96      * Sets the object to expire in the default time
97      *
98      * @param newContents the Cacheable object you want to cache
99      */
100     public CacheEntry(Cacheable newContents) {
101         contents = newContents;
102         expires = -1; /* never expire */
103         created = System.currentTimeMillis();
104     } /* CacheEntry(Cacheable) */
105
106     /**
107      * Constructor 2
108      *
109      * @param newContents the object to cache
110      * @param newExpires how long before the object expires. In millis,
111      * e.g. 1000 = 1 second
112      */
113     public CacheEntry(Cacheable newContents, long newExpires) {
114         contents = newContents;
115         if (newExpires <= 0) {
116             expires = -1;
117         } else {
118             expires = System.currentTimeMillis() + newExpires;
119         }
120         created = System.currentTimeMillis();
121     } /* CacheEntry(Cacheable, long) */
122
123     /**
124      *
125      */
126     public void clearUsedCount() {
127         useCount = 0;
128     } /* clearUsedCount() */
129
130     /**
131      * @return the object
132      */
133     public Cacheable getContents() {
134         return contents;
135     } /* getContents() */
136
137     /**
138      * @return when the object was created
139      */
140     public long getCreated() {
141         return created;
142     } /* getCreated() */
143
144     /**
145      * @return when the object expires
146      */
147     public long getExpires() {
148         return expires;
149     } /* getExpires() */
150
151     /**
152      * @return the object
153      */
154     public String JavaDoc getKey() {
155         return contents.getKey();
156     } /* getKey() */
157
158     /**
159      * Used for figuring out how often this has been used
160      *
161      * @return The number of times this entry has been used
162      */
163     public long getUsedCount() {
164         return useCount;
165     } /* getUsedCount() */
166
167     /**
168      *
169      */
170     public void incrementUsedCount() {
171         useCount++;
172     } /* incrementUsedCount() */
173
174     /**
175      * Set the expiration time for the cache entry.
176      *
177      * @param expiration time in milliseconds to hold the object before it expires.
178      */
179     public void setExpiration(long expiration) {
180         if (expiration < 0) {
181             expires = -1;
182         } else {
183             expires = System.currentTimeMillis() + expiration;
184         }
185     }
186
187     /**
188      * Checks if the object has expired. If it has then it is to be
189      * purged from the cache.
190      *
191      * @return true if the object has expired
192      */
193     public final boolean isExpired() {
194         return (expires > 0 && (System.currentTimeMillis() > expires)) ? true : false;
195     } /* isExpired() */
196
197 } /* CacheEntry */
198
199 /* CacheEntry */
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