SessionCleaner.java

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/*
 * Project: Server for annotations sharing
 * Author: Ing. Jaroslav Dytrych idytrych@fit.vutbr.cz
 * File: SessionCleaner.java
 * Description: Class that provides cleaning of unactive sessions (basic version, not final)
 */

/**
 * @file SessionCleaner.java
 *
 * @brief Class that provides cleaning of unactive sessions (basic version, not final)
 */
package cz.vutbr.fit.knot.annotations.comet;

import cz.vutbr.fit.knot.annotations.app.AppBean;
import cz.vutbr.fit.knot.annotations.app.Constants;
import java.util.Iterator;
import java.util.Timer;
import java.util.TimerTask;

/**
 * Class that provides cleaning of unactive sessions (basic version, not final)
 *
 * @brief Class that provides cleaning of unactive sessions (basic version, not final)
 * @author Martin Petr (xpetrm05)
 */
public class SessionCleaner {
  
  /** timer that execute task CheckAndClean evry time period*/
  private Timer timer = null;
  /** represent maximum time for confirmation of activity from client */
  private long confirmPeriod;
  /** miliseconds in one second constant */
  public static final int SECOND = 1000;
  /** timer tick period */
  public static final int TIMER_PERIOD_S = 60; 

  /**
   * Constructor
   */
  public SessionCleaner() {
    confirmPeriod = Constants.COMET_TIMEOUT_SEC*SECOND*Constants.SESSION_CLEAN_INTERVAL;
    //timer init
    if(timer == null){
      timer = new Timer();
      timer.schedule(new CheckAndClean(),TIMER_PERIOD_S * SECOND, TIMER_PERIOD_S * SECOND);
    }
  }
  
  /**
   * A task that can be scheduled for one-time or repeated execution by a Timer.
   * 
   * @brief Class implement run() method. That method go trough list of sessions 
   * and try to find expired sessions. First kind of expiration occur in case of 
   * client unactivity second kind occur in case of lost connection with annotation 
   * client. This object detect both cases and remove session from sessions list.
   */
  class CheckAndClean extends TimerTask {
    /**
    * Method go trough list of sessions and try to find expired sessions. That sessions 
    * delete.
    */
    @Override
    public void run() {
      synchronized(AppBean.getSessions()){
        Iterator <EditorSession> sessionsIt = AppBean.getSessions().iterator();
        if(sessionsIt == null)return;

        while(sessionsIt.hasNext()){
          EditorSession actualSession = sessionsIt.next();
          long actualTime = System.currentTimeMillis();

          if(actualSession == null || actualTime - actualSession.getLastConfirmTime() > confirmPeriod){
            if(actualSession != null && actualSession.getSyncDocument() != null)
              AppBean.decrementDocumentUsage(actualSession.getSyncDocument().getId());
            sessionsIt.remove();
            continue;
          }
        }
      }  // synchronized(AppBean.getSessions())
    }  // run()
  }  // class CheckAndClean
  
  /**
   * Sets actual time stamp for session confirm time
   *
   * @param sessionId Id of session that will be update
   */
  public void setSessionConfirm(long sessionId){
    if(AppBean.getSession(sessionId) != null){
      AppBean.getSession(sessionId).setLastConfirmTime(System.currentTimeMillis());
    }
  }
}  // public class SessionCleaner