001: /* ====================================================================
002: * The Jcorporate Apache Style Software License, Version 1.2 05-07-2002
003: *
004: * Copyright (c) 1995-2002 Jcorporate Ltd. All rights reserved.
005: *
006: * Redistribution and use in source and binary forms, with or without
007: * modification, are permitted provided that the following conditions
008: * are met:
009: *
010: * 1. Redistributions of source code must retain the above copyright
011: * notice, this list of conditions and the following disclaimer.
012: *
013: * 2. Redistributions in binary form must reproduce the above copyright
014: * notice, this list of conditions and the following disclaimer in
015: * the documentation and/or other materials provided with the
016: * distribution.
017: *
018: * 3. The end-user documentation included with the redistribution,
019: * if any, must include the following acknowledgment:
020: * "This product includes software developed by Jcorporate Ltd.
021: * (http://www.jcorporate.com/)."
022: * Alternately, this acknowledgment may appear in the software itself,
023: * if and wherever such third-party acknowledgments normally appear.
024: *
025: * 4. "Jcorporate" and product names such as "Expresso" must
026: * not be used to endorse or promote products derived from this
027: * software without prior written permission. For written permission,
028: * please contact info@jcorporate.com.
029: *
030: * 5. Products derived from this software may not be called "Expresso",
031: * or other Jcorporate product names; nor may "Expresso" or other
032: * Jcorporate product names appear in their name, without prior
033: * written permission of Jcorporate Ltd.
034: *
035: * 6. No product derived from this software may compete in the same
036: * market space, i.e. framework, without prior written permission
037: * of Jcorporate Ltd. For written permission, please contact
038: * partners@jcorporate.com.
039: *
040: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
041: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
042: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
043: * DISCLAIMED. IN NO EVENT SHALL JCORPORATE LTD OR ITS CONTRIBUTORS
044: * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
045: * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
046: * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
047: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
048: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
049: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
050: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
051: * SUCH DAMAGE.
052: * ====================================================================
053: *
054: * This software consists of voluntary contributions made by many
055: * individuals on behalf of the Jcorporate Ltd. Contributions back
056: * to the project(s) are encouraged when you make modifications.
057: * Please send them to support@jcorporate.com. For more information
058: * on Jcorporate Ltd. and its products, please see
059: * <http://www.jcorporate.com/>.
060: *
061: * Portions of this software are based upon other open source
062: * products and are subject to their respective licenses.
063: */
064:
065: package com.jcorporate.expresso.core.cache;
066:
067: /**
068: * Wrapper for any Cacheable object to be stored in a cache.
069: * This wrapper provides some utility services
070: * to the cacheable object, like maintaining it's usage count
071: * (for the least-frequently-used algorithm
072: * used to free up cache space when needed) and the expiry time
073: * of the object (for caches that use
074: * timed expiry of objects - e.g. keep it cached for x seconds)
075: */
076: public final class CacheEntry {
077:
078: /**
079: * the object to be cached
080: */
081: private Cacheable contents = null;
082:
083: /**
084: * When created *
085: */
086: protected long created = 0;
087:
088: /**
089: * When it expires - default is never to expire *
090: */
091: private long expires = -1;
092: private long useCount = 0;
093:
094: /**
095: * Constructor 1
096: * Sets the object to expire in the default time
097: *
098: * @param newContents the Cacheable object you want to cache
099: */
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 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
195: : false;
196: } /* isExpired() */
197:
198: } /* CacheEntry */
199:
200: /* CacheEntry */
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