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/*
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* SONEWS News Server
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* see AUTHORS for the list of contributors
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package org.sonews.util;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.Map;
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import java.util.Set;
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import java.util.concurrent.ConcurrentHashMap;
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/**
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* Implementation of a Map that will loose its stored values after a
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* configurable amount of time.
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* This class may be used to cache config values for example.
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* @author Christian Lins
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* @since sonews/0.5.0
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*/
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public class TimeoutMap<K, V> extends ConcurrentHashMap<K, V>
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{
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private static final long serialVersionUID = 453453467700345L;
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private int timeout = 60000; // 60 sec
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private transient Map<K, Long> timeoutMap = new HashMap<K, Long>();
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/**
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* Constructor.
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* @param timeout Timeout in milliseconds
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*/
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public TimeoutMap(final int timeout)
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{
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this.timeout = timeout;
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}
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/**
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* Uses default timeout (60 sec).
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*/
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public TimeoutMap()
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{
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}
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/**
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*
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* @param key
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* @return true if key is still valid.
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*/
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protected boolean checkTimeOut(Object key)
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{
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synchronized (this.timeoutMap) {
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if (this.timeoutMap.containsKey(key)) {
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long keytime = this.timeoutMap.get(key);
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if ((System.currentTimeMillis() - keytime) < this.timeout) {
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return true;
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} else {
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remove(key);
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return false;
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}
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} else {
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return false;
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}
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}
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}
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@Override
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public boolean containsKey(Object key)
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{
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return checkTimeOut(key);
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}
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@Override
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public synchronized V get(Object key)
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{
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if (checkTimeOut(key)) {
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return super.get(key);
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} else {
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return null;
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}
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}
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@Override
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public V put(K key, V value)
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{
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synchronized (this.timeoutMap) {
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removeStaleKeys();
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this.timeoutMap.put(key, System.currentTimeMillis());
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return super.put(key, value);
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}
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}
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/**
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* @param arg0
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* @return
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*/
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@Override
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public V remove(Object arg0)
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{
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synchronized (this.timeoutMap) {
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this.timeoutMap.remove(arg0);
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V val = super.remove(arg0);
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return val;
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}
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}
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protected void removeStaleKeys()
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{
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synchronized (this.timeoutMap) {
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Set<Object> keySet = new HashSet<Object>(this.timeoutMap.keySet());
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for (Object key : keySet) {
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// The key/value is removed by the checkTimeOut() method if true
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checkTimeOut(key);
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}
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}
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}
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}
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