org/sonews/util/TimeoutMap.java
author cli
Thu, 20 Aug 2009 16:57:38 +0200
changeset 14 efce4ec25564
parent 1 6fceb66e1ad7
permissions -rw-r--r--
Fix #548: API change; changed parameter type of Storage.getGroupsForList()
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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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    {
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      if(this.timeoutMap.containsKey(key))
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      {
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        long keytime = this.timeoutMap.get(key);
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        if((System.currentTimeMillis() - keytime) < this.timeout)
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        {
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          return true;
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        }
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        else
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        {
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          remove(key);
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          return false;
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        }
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      }
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      else
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      {
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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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    {
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      return super.get(key);
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    }
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    else
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    {
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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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    {
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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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    {
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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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    {
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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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      {
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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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}