001: /*
002: * $Id: GenericCache.java,v 1.5 2002/06/12 23:54:14 skavish Exp $
003: *
004: * ==========================================================================
005: *
006: * The JGenerator Software License, Version 1.0
007: *
008: * Copyright (c) 2000 Dmitry Skavish (skavish@usa.net). All rights reserved.
009: *
010: * Redistribution and use in source and binary forms, with or without
011: * modification, are permitted provided that the following conditions 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, if
022: * any, must include the following acknowlegement:
023: * "This product includes software developed by Dmitry Skavish
024: * (skavish@usa.net, http://www.flashgap.com/)."
025: * Alternately, this acknowlegement may appear in the software itself,
026: * if and wherever such third-party acknowlegements normally appear.
027: *
028: * 4. The name "The JGenerator" must not be used to endorse or promote
029: * products derived from this software without prior written permission.
030: * For written permission, please contact skavish@usa.net.
031: *
032: * 5. Products derived from this software may not be called "The JGenerator"
033: * nor may "The JGenerator" appear in their names without prior written
034: * permission of Dmitry Skavish.
035: *
036: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
037: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
038: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
039: * DISCLAIMED. IN NO EVENT SHALL DMITRY SKAVISH OR THE OTHER
040: * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
041: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
042: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
043: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
044: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
045: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
046: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
047: * SUCH DAMAGE.
048: *
049: */
050:
051: package org.openlaszlo.iv.flash.cache;
052:
053: import org.openlaszlo.iv.flash.api.*;
054: import org.openlaszlo.iv.flash.util.*;
055:
056: import java.util.*;
057:
058: public abstract class GenericCache {
059:
060: protected Hashtable cache = new Hashtable();
061: protected int cacheSize = 0;
062: protected CacheSettings settings = new CacheSettings();
063:
064: public CacheSettings getMySettings() {
065: return settings;
066: }
067:
068: public int getSize() {
069: return cacheSize;
070: }
071:
072: public synchronized void clear() {
073: cache.clear();
074: cacheSize = 0;
075: }
076:
077: protected synchronized boolean addItem(CacheItem item) {
078: //Log.debug("adding item to cache: "+getClass().getName()+", cachesize="+cacheSize+", key='"+item.getKey()+"', expireAfter="+(new Date(item.getExpireAfter()))+", size="+item.getSize() );
079: if (!checkCacheSize(item.getSize())) {
080: //Log.debug(" ... failed. cachesize="+cacheSize);
081: return false;
082: }
083: cache.put(item.getKey(), item);
084: cacheSize += item.getSize();
085: //Log.debug(" ... succeed. cachesize="+cacheSize);
086: return true;
087: }
088:
089: protected synchronized CacheItem getItem(Object key) {
090: CacheItem item = (CacheItem) cache.get(key);
091: if (item == null)
092: return null;
093: if (!isModified(item)
094: && System.currentTimeMillis() <= item.getExpireAfter())
095: return item;
096:
097: // modified or expired - remove from the cache
098: removeItem(item);
099: return null;
100: }
101:
102: protected boolean isModified(CacheItem item) {
103: return false;
104: }
105:
106: /**
107: * Returns true if there is enough place
108: */
109: protected boolean checkCacheSize(int size) {
110: if (cacheSize + size <= settings.getMaxSize())
111: return true;
112: if (!settings.isRecycle())
113: return false;
114: recycle(size);
115: return cacheSize + size <= settings.getMaxSize();
116: }
117:
118: /**
119: * Try to recycle at least 'size' bytes
120: */
121: protected synchronized void recycle(int size) {
122: if (cache.size() == 0)
123: return;
124: //Log.log( Resource.STR, "Recycling cache("+cacheSize+")" );
125:
126: // sort list in ascending order, so older elements come first
127: ArrayList l = new ArrayList(cache.values());
128: Collections.sort(l, new Comparator() {
129: public int compare(Object o1, Object o2) {
130: return (int) (((CacheItem) o1).getCacheTime() - ((CacheItem) o2)
131: .getCacheTime());
132: }
133: });
134:
135: // recycle cache and remove stale objects at the same time
136: long now = System.currentTimeMillis();
137: for (int i = 0; i < l.size(); i++) {
138: CacheItem item = (CacheItem) l.get(i);
139: if (size > 0 || now > item.getExpireAfter()) {
140: size -= item.getSize();
141: removeItem(item);
142: }
143: }
144: //Log.log( Resource.STR, "Recycling cache("+cacheSize+") DONE" );
145: }
146:
147: protected synchronized void removeItem(CacheItem item) {
148: cacheSize -= item.getSize();
149: cache.remove(item.getKey());
150: }
151:
152: }
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