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Simple is a high performance asynchronous HTTP server for Java
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/*
 * Maintainer.java May 2007
 *
 * Copyright (C) 2007, Niall Gallagher 
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General 
 * Public License along with this library; if not, write to the 
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
 * Boston, MA  02111-1307  USA
 */

package org.simpleframework.http.session;

import java.util.concurrent.TimeUnit;

import org.simpleframework.util.lease.Lease;
import org.simpleframework.util.lease.LeaseException;
import org.simpleframework.util.lease.LeaseManager;
import org.simpleframework.util.lease.LeaseMap;

/**
 * The Maintainer object is used to manage all life cycle
 * events for sessions. This is used to start and renew all leases
 * issued. The start life cycle event is used when the session is first
 * created, this will lease the new session for some fixed duration. 
 * The renew event is performed when an existing session is accessed 
 * again so that the session can be maintained for the default period.
 * 
 * @author Niall Gallagher
 */
class Maintainer implements Controller {
   
   /**
    * This is the lease manager used to create the lease objects.
    */
   private final LeaseManager manager;
   
   /**    
    * This is the lease map used to maintain the leases by key.
    */
   private final LeaseMap map;
   
   /**
    * This is the time unit used for the fixed lease duration.
    */
   private final TimeUnit unit;
   
   /**
    * This is the duration the lease objects are renewed for.
    */
   private final long duration;
   
   /**
    * Constructor for the Maintainer object. This is used 
    * to maintain a lease for a resource using only the key for that
    * resource. Each renewal of the lease is performed using a fixed
    * duration so that the the time does not need to be specified.
    * 
    * @param manager this is the manager used to create the leases
    * @param duration this is the fixed duration to renew for
    * @param unit this is the unit of measurement for the duration
    */
   public Maintainer(LeaseManager manager, long duration, TimeUnit unit) {
      this.map = new LeaseMap();
      this.manager = manager;
      this.duration = duration;
      this.unit = unit;
   }
   
   /**
    * The start method is used when a session is to 
    * be created for the first time. This will ensure that the key 
    * specified is used to dispose of the session when its idle
    * timeout has expired. 
    * 
    * @param key this is the unique key identifying the session
    */
   public Lease start(T key) throws LeaseException {
      Lease lease = manager.lease(key, duration, unit);
      
      if(lease != null) {
         map.put(key, lease);
      }
      return lease;
   }   
   
   /**
    * The renew method is used when a session has been 
    * accessed for a again. This ensures that the key specified is 
    * used to dispose of the session when its idle timeout expires. 
    * 
    * @param key this is the unique key identifying the session
    */
   public void renew(T key) throws LeaseException {
      Lease lease = map.get(key);
      
      if(lease == null) {
         throw new SessionException("Session does not exist");
      }
      lease.renew(duration, unit);    
   }
   
   /**
    * The cancel method is used when a session is no
    * longer required and is to be disposed of. This is typically
    * invoked by a web application to release occupied resources.
    * 
    * @param key this is the unique key identifying the session
    */
   public void cancel(T key) throws LeaseException {
      Lease lease = map.remove(key);
      
      if(lease == null) {
         throw new SessionException("Session does not exist");         
      }
   }
}