ExpiringCache.java revision 51b1b6997fd3f980076b8081f7f1165ccc2a4008
151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski/* 251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * Copyright (c) 2002, 2004, Oracle and/or its affiliates. All rights reserved. 351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * 551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * This code is free software; you can redistribute it and/or modify it 651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * under the terms of the GNU General Public License version 2 only, as 751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * published by the Free Software Foundation. Oracle designates this 851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * particular file as subject to the "Classpath" exception as provided 951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * by Oracle in the LICENSE file that accompanied this code. 1051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * 1151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * This code is distributed in the hope that it will be useful, but WITHOUT 1251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 1351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 1451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * version 2 for more details (a copy is included in the LICENSE file that 1551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * accompanied this code). 1651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * 1751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * You should have received a copy of the GNU General Public License version 1851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * 2 along with this work; if not, write to the Free Software Foundation, 1951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 2051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * 2151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 2251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * or visit www.oracle.com if you need additional information or have any 2351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski * questions. 2451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski */ 2551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 2651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski/* 2751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski */ 2851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 2951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebskipackage java.io; 3051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 3151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebskiimport java.util.Iterator; 3251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebskiimport java.util.Map; 3351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebskiimport java.util.LinkedHashMap; 3451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebskiimport java.util.Set; 3551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 3651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebskiclass ExpiringCache { 3751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private long millisUntilExpiration; 3851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private Map map; 3951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski // Clear out old entries every few queries 4051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private int queryCount; 4151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private int queryOverflow = 300; 4251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private int MAX_ENTRIES = 200; 4351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 4451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski static class Entry { 4551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private long timestamp; 4651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private String val; 4751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 4851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski Entry(long timestamp, String val) { 4951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski this.timestamp = timestamp; 5051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski this.val = val; 5151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 5251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 5351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski long timestamp() { return timestamp; } 5451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski void setTimestamp(long timestamp) { this.timestamp = timestamp; } 5551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 5651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski String val() { return val; } 5751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski void setVal(String val) { this.val = val; } 5851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 5951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 6051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski ExpiringCache() { 6151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski this(30000); 6251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 6351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 6451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski ExpiringCache(long millisUntilExpiration) { 6551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski this.millisUntilExpiration = millisUntilExpiration; 6651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski map = new LinkedHashMap() { 6751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski protected boolean removeEldestEntry(Map.Entry eldest) { 6851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski return size() > MAX_ENTRIES; 6951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 7051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski }; 7151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 7251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 7351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski synchronized String get(String key) { 7451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski if (++queryCount >= queryOverflow) { 7551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski cleanup(); 7651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 7751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski Entry entry = entryFor(key); 7851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski if (entry != null) { 7951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski return entry.val(); 8051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 8151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski return null; 8251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 8351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 8451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski synchronized void put(String key, String val) { 8551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski if (++queryCount >= queryOverflow) { 8651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski cleanup(); 8751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 8851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski Entry entry = entryFor(key); 8951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski if (entry != null) { 9051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski entry.setTimestamp(System.currentTimeMillis()); 9151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski entry.setVal(val); 9251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } else { 9351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski map.put(key, new Entry(System.currentTimeMillis(), val)); 9451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 9551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 9651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 9751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski synchronized void clear() { 9851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski map.clear(); 9951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 10051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 10151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private Entry entryFor(String key) { 10251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski Entry entry = (Entry) map.get(key); 10351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski if (entry != null) { 10451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski long delta = System.currentTimeMillis() - entry.timestamp(); 10551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski if (delta < 0 || delta >= millisUntilExpiration) { 10651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski map.remove(key); 10751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski entry = null; 10851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 10951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 11051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski return entry; 11151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 11251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski 11351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski private void cleanup() { 11451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski Set keySet = map.keySet(); 11551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski // Avoid ConcurrentModificationExceptions 11651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski String[] keys = new String[keySet.size()]; 11751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski int i = 0; 11851b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski for (Iterator iter = keySet.iterator(); iter.hasNext(); ) { 11951b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski String key = (String) iter.next(); 12051b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski keys[i++] = key; 12151b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 12251b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski for (int j = 0; j < keys.length; j++) { 12351b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski entryFor(keys[j]); 12451b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 12551b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski queryCount = 0; 12651b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski } 12751b1b6997fd3f980076b8081f7f1165ccc2a4008Piotr Jastrzebski} 128