001: package com.protomatter.util;
002:
003: /**
004: * {{{ The Protomatter Software License, Version 1.0
005: * derived from The Apache Software License, Version 1.1
006: *
007: * Copyright (c) 1998-2002 Nate Sammons. All rights reserved.
008: *
009: * Redistribution and use in source and binary forms, with or without
010: * modification, are permitted provided that the following conditions
011: * are met:
012: *
013: * 1. Redistributions of source code must retain the above copyright
014: * notice, this list of conditions and the following disclaimer.
015: *
016: * 2. Redistributions in binary form must reproduce the above copyright
017: * notice, this list of conditions and the following disclaimer in
018: * the documentation and/or other materials provided with the
019: * distribution.
020: *
021: * 3. The end-user documentation included with the redistribution,
022: * if any, must include the following acknowledgment:
023: * "This product includes software developed for the
024: * Protomatter Software Project
025: * (http://protomatter.sourceforge.net/)."
026: * Alternately, this acknowledgment may appear in the software itself,
027: * if and wherever such third-party acknowledgments normally appear.
028: *
029: * 4. The names "Protomatter" and "Protomatter Software Project" must
030: * not be used to endorse or promote products derived from this
031: * software without prior written permission. For written
032: * permission, please contact support@protomatter.com.
033: *
034: * 5. Products derived from this software may not be called "Protomatter",
035: * nor may "Protomatter" appear in their name, without prior written
036: * permission of the Protomatter Software Project
037: * (support@protomatter.com).
038: *
039: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
040: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
041: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
042: * DISCLAIMED. IN NO EVENT SHALL THE PROTOMATTER SOFTWARE PROJECT OR
043: * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
044: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
045: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
046: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
047: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
048: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
049: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
050: * SUCH DAMAGE. }}}
051: */
052:
053: /**
054: * A cache that uses soft references and will also expire
055: * cache values after a given period of time.
056: */
057: public class ExpiringSoftReferenceCache extends SoftReferenceCache {
058: private long timeout = 0;
059:
060: /**
061: * Create a new timed soft reference cache with the given timeout.
062: */
063: public ExpiringSoftReferenceCache(long timeout) {
064: super ();
065: this .timeout = timeout;
066: }
067:
068: /**
069: * Put a value into the cache, possibly clobbering the
070: * old value if one exists.
071: */
072: public void put(Object key, Object val) {
073: super .put(key, new CacheValue(val));
074: }
075:
076: /**
077: * Get a value from the cache.
078: */
079: public Object get(Object key) {
080: CacheValue value = (CacheValue) super .get(key);
081: if (value != null) {
082: long now = System.currentTimeMillis();
083: if ((value.getCreateTime() + this .timeout) >= now) {
084: return value.getValue();
085: } else {
086: clear(key);
087: }
088: }
089: return null;
090: }
091:
092: private class CacheValue {
093: private long createTime = 0;
094: private Object value = null;
095:
096: public CacheValue(Object value) {
097: this .value = value;
098: this .createTime = System.currentTimeMillis();
099: }
100:
101: public Object getValue() {
102: return this .value;
103: }
104:
105: public long getCreateTime() {
106: return this.createTime;
107: }
108: }
109: }
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