lifeguardthread.java

Java Database connection pool

/*
 *  PoolMan Java Object Pooling and Caching Library
 *  Copyright (C) 1999-2001 The Code Studio
 *
 *  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; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  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.
 *
 *  The full license is located at the root of this distribution
 *  in the LICENSE file.
 */
package com.codestudio.util;


/**
 * Asks SmartObjects to manage themselves and clean up if necessary.
 * For JDBCPool objects, this means asking hanging connections to
 * clear themselves and either return to their respective pools or
 * to dispose of themselves.
 *<p>
 * LifeGuardThread attempts to salvage objects that may still be of use;
 * PoolSkimmerThread also monitors ObjectPool instances, but
 * PoolSkimmerThread is a little harsher and mechanical -- it simply
 * disposes of objects that are already dead or useless.
 *<br>
 *@see PoolSkimmerThread
 */
public class LifeGuardThread implements Runnable {

    /** The ObjectPool whose Objects this Thread is monitoring. */
    private ObjectPool pool;

    /** The standard user timeout for each SmartObject, used to time checks. */
    private long timeout;

    public LifeGuardThread(int timeoutSecs, ObjectPool p) {
        this.pool = p;
        this.timeout = (timeoutSecs * 1000);
    }

    public void run() {

        for (; ;) {

            // do nothing until something is checked out
            while (this.pool.numCheckedOutObjects() <= 0) {
                try {
                    //System.out.println("LifeguardThread: waiting for " + this.timeout +
                    //" millis with numCheckedOut=" + this.pool.numCheckedOutObjects());
                    Thread.sleep(this.timeout);
                } catch (InterruptedException ie) {
                }
            }

            // when something is checked out, wait the usertimeout period then act
            try {
                Thread.sleep(this.timeout);
            } catch (InterruptedException iee) {
            }

            this.pool.checkTimeout();

        }

    }

}