/*
 * Copyright 1999-2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.frameworkset.commons.pool.impl;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.Timer;
import java.util.TimerTask;

import com.frameworkset.commons.pool.BaseObjectPool;
import com.frameworkset.commons.pool.ObjectPool;
import com.frameworkset.commons.pool.PoolableObjectFactory;
import com.frameworkset.commons.pool.impl.GenericKeyedObjectPool.ObjectTimestampPair;

/**
 * A configurable {@link ObjectPool} implementation.
 * <p>
 * When coupled with the appropriate {@link PoolableObjectFactory},
 * <tt>GenericObjectPool</tt> provides robust pooling functionality for
 * arbitrary objects.
 * <p>
 * A <tt>GenericObjectPool</tt> provides a number of configurable parameters:
 * <ul>
 *  <li>
 *    {@link #setMaxActive <i>maxActive</i>} controls the maximum number of objects that can
 *    be borrowed from the pool at one time.  When non-positive, there
 *    is no limit to the number of objects that may be active at one time.
 *    When {@link #setMaxActive <i>maxActive</i>} is exceeded, the pool is said to be exhausted.
 *  </li>
 *  <li>
 *    {@link #setMaxIdle <i>maxIdle</i>} controls the maximum number of objects that can
 *    sit idle in the pool at any time.  When negative, there
 *    is no limit to the number of objects that may be idle at one time.
 *  </li>
 *  <li>
 *    {@link #setWhenExhaustedAction <i>whenExhaustedAction</i>} specifies the
 *    behaviour of the {@link #borrowObject} method when the pool is exhausted:
 *    <ul>
 *    <li>
 *      When {@link #setWhenExhaustedAction <i>whenExhaustedAction</i>} is
 *      {@link #WHEN_EXHAUSTED_FAIL}, {@link #borrowObject} will throw
 *      a {@link NoSuchElementException}
 *    </li>
 *    <li>
 *      When {@link #setWhenExhaustedAction <i>whenExhaustedAction</i>} is
 *      {@link #WHEN_EXHAUSTED_GROW}, {@link #borrowObject} will create a new
 *      object and return it(essentially making {@link #setMaxActive <i>maxActive</i>}
 *      meaningless.)
 *    </li>
 *    <li>
 *      When {@link #setWhenExhaustedAction <i>whenExhaustedAction</i>}
 *      is {@link #WHEN_EXHAUSTED_BLOCK}, {@link #borrowObject} will block
 *      (invoke {@link Object#wait} until a new or idle object is available.
 *      If a positive {@link #setMaxWait <i>maxWait</i>}
 *      value is supplied, the {@link #borrowObject} will block for at
 *      most that many milliseconds, after which a {@link NoSuchElementException}
 *      will be thrown.  If {@link #setMaxWait <i>maxWait</i>} is non-positive,
 *      the {@link #borrowObject} method will block indefinitely.
 *    </li>
 *    </ul>
 *  </li>
 *  <li>
 *    When {@link #setTestOnBorrow <i>testOnBorrow</i>} is set, the pool will
 *    attempt to validate each object before it is returned from the
 *    {@link #borrowObject} method. (Using the provided factory's
 *    {@link PoolableObjectFactory#validateObject} method.)  Objects that fail
 *    to validate will be dropped from the pool, and a different object will
 *    be borrowed.
 *  </li>
 *  <li>
 *    When {@link #setTestOnReturn <i>testOnReturn</i>} is set, the pool will
 *    attempt to validate each object before it is returned to the pool in the
 *    {@link #returnObject} method. (Using the provided factory's
 *    {@link PoolableObjectFactory#validateObject}
 *    method.)  Objects that fail to validate will be dropped from the pool.
 *  </li>
 * </ul>
 * <p>
 * Optionally, one may configure the pool to examine and possibly evict objects as they
 * sit idle in the pool.  This is performed by an "idle object eviction" thread, which
 * runs asychronously.  The idle object eviction thread may be configured using the
 * following attributes:
 * <ul>
 *  <li>
 *   {@link #setTimeBetweenEvictionRunsMillis <i>timeBetweenEvictionRunsMillis</i>}
 *   indicates how long the eviction thread should sleep before "runs" of examining
 *   idle objects.  When non-positive, no eviction thread will be launched.
 *  </li>
 *  <li>
 *   {@link #setMinEvictableIdleTimeMillis <i>minEvictableIdleTimeMillis</i>}
 *   specifies the minimum amount of time that an object may sit idle in the pool
 *   before it is eligable for eviction due to idle time.  When non-positive, no object
 *   will be dropped from the pool due to idle time alone.
 *  </li>
 *  <li>
 *   {@link #setTestWhileIdle <i>testWhileIdle</i>} indicates whether or not idle
 *   objects should be validated using the factory's
 *   {@link PoolableObjectFactory#validateObject} method.  Objects
 *   that fail to validate will be dropped from the pool.
 *  </li>
 * </ul>
 * <p>
 * GenericObjectPool is not usable without a {@link PoolableObjectFactory}.  A
 * non-<code>null</code> factory must be provided either as a constructor argument
 * or via a call to {@link #setFactory} before the pool is used.
 *
 * @see GenericKeyedObjectPool
 * @author Rodney Waldhoff
 * @author Dirk Verbeeck
 * @version $Revision: 390563 $ $Date: 2006-03-31 20:28:14 -0500 (Fri, 31 Mar 2006) $
 */
public class GenericObjectPool extends BaseObjectPool implements ObjectPool {

    //--- public constants -------------------------------------------

    /**
     * A "when exhausted action" type indicating that when the pool is
     * exhausted (i.e., the maximum number of active objects has
     * been reached), the {@link #borrowObject}
     * method should fail, throwing a {@link NoSuchElementException}.
     * @see #WHEN_EXHAUSTED_BLOCK
     * @see #WHEN_EXHAUSTED_GROW
     * @see #setWhenExhaustedAction
     */
    public static final byte WHEN_EXHAUSTED_FAIL   = 0;

    /**
     * A "when exhausted action" type indicating that when the pool
     * is exhausted (i.e., the maximum number
     * of active objects has been reached), the {@link #borrowObject}
     * method should block until a new object is available, or the
     * {@link #getMaxWait maximum wait time} has been reached.
     * @see #WHEN_EXHAUSTED_FAIL
     * @see #WHEN_EXHAUSTED_GROW
     * @see #setMaxWait
     * @see #getMaxWait
     * @see #setWhenExhaustedAction
     */
    public static final byte WHEN_EXHAUSTED_BLOCK  = 1;

    /**
     * A "when exhausted action" type indicating that when the pool is
     * exhausted (i.e., the maximum number
     * of active objects has been reached), the {@link #borrowObject}
     * method should simply create a new object anyway.
     * @see #WHEN_EXHAUSTED_FAIL
     * @see #WHEN_EXHAUSTED_GROW
     * @see #setWhenExhaustedAction
     */
    public static final byte WHEN_EXHAUSTED_GROW   = 2;

    /**
     * The default cap on the number of "sleeping" instances in the pool.
     * @see #getMaxIdle
     * @see #setMaxIdle
     */
    public static final int DEFAULT_MAX_IDLE  = 8;

    /**
     * The default minimum number of "sleeping" instances in the pool
     * before before the evictor thread (if active) spawns new objects.
     * @see #getMinIdle
     * @see #setMinIdle
     */
    public static final int DEFAULT_MIN_IDLE = 0;

    /**
     * The default cap on the total number of active instances from the pool.
     * @see #getMaxActive
     */
    public static final int DEFAULT_MAX_ACTIVE  = 8;

    /**
     * The default "when exhausted action" for the pool.
     * @see #WHEN_EXHAUSTED_BLOCK
     * @see #WHEN_EXHAUSTED_FAIL
     * @see #WHEN_EXHAUSTED_GROW
     * @see #setWhenExhaustedAction
     */
    public static final byte DEFAULT_WHEN_EXHAUSTED_ACTION = WHEN_EXHAUSTED_BLOCK;

    /**
     * The default maximum amount of time (in millis) the
     * {@link #borrowObject} method should block before throwing
     * an exception when the pool is exhausted and the
     * {@link #getWhenExhaustedAction "when exhausted" action} is
     * {@link #WHEN_EXHAUSTED_BLOCK}.
     * @see #getMaxWait
     * @see #setMaxWait
     */
    public static final long DEFAULT_MAX_WAIT = -1L;

    /**
     * The default "test on borrow" value.
     * @see #getTestOnBorrow
     * @see #setTestOnBorrow
     */
    public static final boolean DEFAULT_TEST_ON_BORROW = false;

    /**
     * The default "test on return" value.
     * @see #getTestOnReturn
     * @see #setTestOnReturn
     */
    public static final boolean DEFAULT_TEST_ON_RETURN = false;

    /**
     * The default "test while idle" value.
     * @see #getTestWhileIdle
     * @see #setTestWhileIdle
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public static final boolean DEFAULT_TEST_WHILE_IDLE = false;

    /**
     * The default "time between eviction runs" value.
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public static final long DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS = -1L;

    /**
     * The default number of objects to examine per run in the
     * idle object evictor.
     * @see #getNumTestsPerEvictionRun
     * @see #setNumTestsPerEvictionRun
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public static final int DEFAULT_NUM_TESTS_PER_EVICTION_RUN = 3;

    /**
     * The default value for {@link #getMinEvictableIdleTimeMillis}.
     * @see #getMinEvictableIdleTimeMillis
     * @see #setMinEvictableIdleTimeMillis
     */
    public static final long DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS = 1000L * 60L * 30L;

    /**
     * The default value for {@link #getSoftMinEvictableIdleTimeMillis}.
     * @see #getSoftMinEvictableIdleTimeMillis
     * @see #setSoftMinEvictableIdleTimeMillis
     */
    public static final long DEFAULT_SOFT_MIN_EVICTABLE_IDLE_TIME_MILLIS = -1;

    //--- package constants -------------------------------------------

    /**
     * Idle object evition Timer. Shared between all {@link GenericObjectPool}s and {@link GenericKeyedObjectPool} s.
     */
    static final Timer EVICTION_TIMER = new Timer(true);

    //--- constructors -----------------------------------------------

    /**
     * Create a new <tt>GenericObjectPool</tt>.
     */
    public GenericObjectPool() {
        this(null,DEFAULT_MAX_ACTIVE,DEFAULT_WHEN_EXHAUSTED_ACTION,DEFAULT_MAX_WAIT,DEFAULT_MAX_IDLE,DEFAULT_MIN_IDLE,DEFAULT_TEST_ON_BORROW,DEFAULT_TEST_ON_RETURN,DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,DEFAULT_NUM_TESTS_PER_EVICTION_RUN,DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS,DEFAULT_TEST_WHILE_IDLE);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     */
    public GenericObjectPool(PoolableObjectFactory factory) {
        this(factory,DEFAULT_MAX_ACTIVE,DEFAULT_WHEN_EXHAUSTED_ACTION,DEFAULT_MAX_WAIT,DEFAULT_MAX_IDLE,DEFAULT_MIN_IDLE,DEFAULT_TEST_ON_BORROW,DEFAULT_TEST_ON_RETURN,DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,DEFAULT_NUM_TESTS_PER_EVICTION_RUN,DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS,DEFAULT_TEST_WHILE_IDLE);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param config a non-<tt>null</tt> {@link GenericObjectPool.Config} describing my configuration
     */
    public GenericObjectPool(PoolableObjectFactory factory, GenericObjectPool.Config config) {
        this(factory,config.maxActive,config.whenExhaustedAction,config.maxWait,config.maxIdle,config.minIdle,config.testOnBorrow,config.testOnReturn,config.timeBetweenEvictionRunsMillis,config.numTestsPerEvictionRun,config.minEvictableIdleTimeMillis,config.testWhileIdle);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
     */
    public GenericObjectPool(PoolableObjectFactory factory, int maxActive) {
        this(factory,maxActive,DEFAULT_WHEN_EXHAUSTED_ACTION,DEFAULT_MAX_WAIT,DEFAULT_MAX_IDLE,DEFAULT_MIN_IDLE,DEFAULT_TEST_ON_BORROW,DEFAULT_TEST_ON_RETURN,DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,DEFAULT_NUM_TESTS_PER_EVICTION_RUN,DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS,DEFAULT_TEST_WHILE_IDLE);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
     * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #getWhenExhaustedAction})
     * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted an and <i>whenExhaustedAction</i> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #getMaxWait})
     */
    public GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait) {
        this(factory,maxActive,whenExhaustedAction,maxWait,DEFAULT_MAX_IDLE,DEFAULT_MIN_IDLE,DEFAULT_TEST_ON_BORROW,DEFAULT_TEST_ON_RETURN,DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,DEFAULT_NUM_TESTS_PER_EVICTION_RUN,DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS,DEFAULT_TEST_WHILE_IDLE);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
     * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #getWhenExhaustedAction})
     * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted an and <i>whenExhaustedAction</i> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #getMaxWait})
     * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject} method (see {@link #getTestOnBorrow})
     * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject} method (see {@link #getTestOnReturn})
     */
    public GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, boolean testOnBorrow, boolean testOnReturn) {
        this(factory,maxActive,whenExhaustedAction,maxWait,DEFAULT_MAX_IDLE,DEFAULT_MIN_IDLE,testOnBorrow,testOnReturn,DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,DEFAULT_NUM_TESTS_PER_EVICTION_RUN,DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS,DEFAULT_TEST_WHILE_IDLE);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
     * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #getWhenExhaustedAction})
     * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted an and <i>whenExhaustedAction</i> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #getMaxWait})
     * @param maxIdle the maximum number of idle objects in my pool (see {@link #getMaxIdle})
     */
    public GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle) {
        this(factory,maxActive,whenExhaustedAction,maxWait,maxIdle,DEFAULT_MIN_IDLE,DEFAULT_TEST_ON_BORROW,DEFAULT_TEST_ON_RETURN,DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,DEFAULT_NUM_TESTS_PER_EVICTION_RUN,DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS,DEFAULT_TEST_WHILE_IDLE);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
     * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #getWhenExhaustedAction})
     * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted an and <i>whenExhaustedAction</i> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #getMaxWait})
     * @param maxIdle the maximum number of idle objects in my pool (see {@link #getMaxIdle})
     * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject} method (see {@link #getTestOnBorrow})
     * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject} method (see {@link #getTestOnReturn})
     */
    public GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, boolean testOnBorrow, boolean testOnReturn) {
        this(factory,maxActive,whenExhaustedAction,maxWait,maxIdle,DEFAULT_MIN_IDLE,testOnBorrow,testOnReturn,DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,DEFAULT_NUM_TESTS_PER_EVICTION_RUN,DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS,DEFAULT_TEST_WHILE_IDLE);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
     * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
     * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted an and <i>whenExhaustedAction</i> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
     * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
     * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject} method (see {@link #setTestOnBorrow})
     * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject} method (see {@link #setTestOnReturn})
     * @param timeBetweenEvictionRunsMillis the amount of time (in milliseconds) to sleep between examining idle objects for eviction (see {@link #setTimeBetweenEvictionRunsMillis})
     * @param numTestsPerEvictionRun the number of idle objects to examine per run within the idle object eviction thread (if any) (see {@link #setNumTestsPerEvictionRun})
     * @param minEvictableIdleTimeMillis the minimum number of milliseconds an object can sit idle in the pool before it is eligable for evcition (see {@link #setMinEvictableIdleTimeMillis})
     * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any (see {@link #setTestWhileIdle})
     */
    public GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, boolean testOnBorrow, boolean testOnReturn, long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis, boolean testWhileIdle) {
        this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, DEFAULT_MIN_IDLE, testOnBorrow, testOnReturn, timeBetweenEvictionRunsMillis, numTestsPerEvictionRun, minEvictableIdleTimeMillis, testWhileIdle);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
     * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
     * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted an and <i>whenExhaustedAction</i> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
     * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
     * @param minIdle the minimum number of idle objects in my pool (see {@link #setMinIdle})
     * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject} method (see {@link #setTestOnBorrow})
     * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject} method (see {@link #setTestOnReturn})
     * @param timeBetweenEvictionRunsMillis the amount of time (in milliseconds) to sleep between examining idle objects for eviction (see {@link #setTimeBetweenEvictionRunsMillis})
     * @param numTestsPerEvictionRun the number of idle objects to examine per run within the idle object eviction thread (if any) (see {@link #setNumTestsPerEvictionRun})
     * @param minEvictableIdleTimeMillis the minimum number of milliseconds an object can sit idle in the pool before it is eligable for evcition (see {@link #setMinEvictableIdleTimeMillis})
     * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any (see {@link #setTestWhileIdle})
     */
    public GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, int minIdle, boolean testOnBorrow, boolean testOnReturn, long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis, boolean testWhileIdle) {
        this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, minIdle, testOnBorrow, testOnReturn, timeBetweenEvictionRunsMillis, numTestsPerEvictionRun, minEvictableIdleTimeMillis, testWhileIdle, DEFAULT_SOFT_MIN_EVICTABLE_IDLE_TIME_MILLIS);
    }

    /**
     * Create a new <tt>GenericObjectPool</tt> using the specified values.
     * @param factory the (possibly <tt>null</tt>)PoolableObjectFactory to use to create, validate and destroy objects
     * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
     * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
     * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted an and <i>whenExhaustedAction</i> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
     * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
     * @param minIdle the minimum number of idle objects in my pool (see {@link #setMinIdle})
     * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject} method (see {@link #setTestOnBorrow})
     * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject} method (see {@link #setTestOnReturn})
     * @param timeBetweenEvictionRunsMillis the amount of time (in milliseconds) to sleep between examining idle objects for eviction (see {@link #setTimeBetweenEvictionRunsMillis})
     * @param numTestsPerEvictionRun the number of idle objects to examine per run within the idle object eviction thread (if any) (see {@link #setNumTestsPerEvictionRun})
     * @param minEvictableIdleTimeMillis the minimum number of milliseconds an object can sit idle in the pool before it is eligable for evcition (see {@link #setMinEvictableIdleTimeMillis})
     * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any (see {@link #setTestWhileIdle})
     * @param softMinEvictableIdleTimeMillis the minimum number of milliseconds an object can sit idle in the pool before it is eligable for evcition with the extra condition that at least "minIdle" amount of object remain in the pool. (see {@link #setSoftMinEvictableIdleTimeMillis})
     */
    public GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, int minIdle, boolean testOnBorrow, boolean testOnReturn, long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis, boolean testWhileIdle, long softMinEvictableIdleTimeMillis) {
        _factory = factory;
        _maxActive = maxActive;
        switch(whenExhaustedAction) {
            case WHEN_EXHAUSTED_BLOCK:
            case WHEN_EXHAUSTED_FAIL:
            case WHEN_EXHAUSTED_GROW:
                _whenExhaustedAction = whenExhaustedAction;
                break;
            default:
                throw new IllegalArgumentException("whenExhaustedAction " + whenExhaustedAction + " not recognized.");
        }
        _maxWait = maxWait;
        _maxIdle = maxIdle;
        _minIdle = minIdle;
        _testOnBorrow = testOnBorrow;
        _testOnReturn = testOnReturn;
        _timeBetweenEvictionRunsMillis = timeBetweenEvictionRunsMillis;
        _numTestsPerEvictionRun = numTestsPerEvictionRun;
        _minEvictableIdleTimeMillis = minEvictableIdleTimeMillis;
        _softMinEvictableIdleTimeMillis = softMinEvictableIdleTimeMillis;
        _testWhileIdle = testWhileIdle;

        _pool = new LinkedList();
        startEvictor(_timeBetweenEvictionRunsMillis);
    }

    //--- public methods ---------------------------------------------

    //--- configuration methods --------------------------------------

    /**
     * Returns the cap on the total number of active instances from my pool.
     * @return the cap on the total number of active instances from my pool.
     * @see #setMaxActive
     */
    public synchronized int getMaxActive() {
        return _maxActive;
    }

    /**
     * Sets the cap on the total number of active instances from my pool.
     * @param maxActive The cap on the total number of active instances from my pool.
     *                  Use a negative value for an infinite number of instances.
     * @see #getMaxActive
     */
    public synchronized void setMaxActive(int maxActive) {
        _maxActive = maxActive;
        notifyAll();
    }

    /**
     * Returns the action to take when the {@link #borrowObject} method
     * is invoked when the pool is exhausted (the maximum number
     * of "active" objects has been reached).
     *
     * @return one of {@link #WHEN_EXHAUSTED_BLOCK}, {@link #WHEN_EXHAUSTED_FAIL} or {@link #WHEN_EXHAUSTED_GROW}
     * @see #setWhenExhaustedAction
     */
    public synchronized byte getWhenExhaustedAction() {
        return _whenExhaustedAction;
    }

    /**
     * Sets the action to take when the {@link #borrowObject} method
     * is invoked when the pool is exhausted (the maximum number
     * of "active" objects has been reached).
     *
     * @param whenExhaustedAction the action code, which must be one of
     *        {@link #WHEN_EXHAUSTED_BLOCK}, {@link #WHEN_EXHAUSTED_FAIL},
     *        or {@link #WHEN_EXHAUSTED_GROW}
     * @see #getWhenExhaustedAction
     */
    public synchronized void setWhenExhaustedAction(byte whenExhaustedAction) {
        switch(whenExhaustedAction) {
            case WHEN_EXHAUSTED_BLOCK:
            case WHEN_EXHAUSTED_FAIL:
            case WHEN_EXHAUSTED_GROW:
                _whenExhaustedAction = whenExhaustedAction;
                notifyAll();
                break;
            default:
                throw new IllegalArgumentException("whenExhaustedAction " + whenExhaustedAction + " not recognized.");
        }
    }


    /**
     * Returns the maximum amount of time (in milliseconds) the
     * {@link #borrowObject} method should block before throwing
     * an exception when the pool is exhausted and the
     * {@link #setWhenExhaustedAction "when exhausted" action} is
     * {@link #WHEN_EXHAUSTED_BLOCK}.
     *
     * When less than 0, the {@link #borrowObject} method
     * may block indefinitely.
     *
     * @see #setMaxWait
     * @see #setWhenExhaustedAction
     * @see #WHEN_EXHAUSTED_BLOCK
     */
    public synchronized long getMaxWait() {
        return _maxWait;
    }

    /**
     * Sets the maximum amount of time (in milliseconds) the
     * {@link #borrowObject} method should block before throwing
     * an exception when the pool is exhausted and the
     * {@link #setWhenExhaustedAction "when exhausted" action} is
     * {@link #WHEN_EXHAUSTED_BLOCK}.
     *
     * When less than 0, the {@link #borrowObject} method
     * may block indefinitely.
     *
     * @see #getMaxWait
     * @see #setWhenExhaustedAction
     * @see #WHEN_EXHAUSTED_BLOCK
     */
    public synchronized void setMaxWait(long maxWait) {
        _maxWait = maxWait;
        notifyAll();
    }

    /**
     * Returns the cap on the number of "idle" instances in the pool.
     * @return the cap on the number of "idle" instances in the pool.
     * @see #setMaxIdle
     */
    public synchronized int getMaxIdle() {
        return _maxIdle;
    }

    /**
     * Sets the cap on the number of "idle" instances in the pool.
     * @param maxIdle The cap on the number of "idle" instances in the pool.
     *                Use a negative value to indicate an unlimited number
     *                of idle instances.
     * @see #getMaxIdle
     */
    public synchronized void setMaxIdle(int maxIdle) {
        _maxIdle = maxIdle;
        notifyAll();
    }

    /**
     * Sets the minimum number of objects allowed in the pool
     * before the evictor thread (if active) spawns new objects.
     * (Note no objects are created when: numActive + numIdle >= maxActive)
     *
     * @param minIdle The minimum number of objects.
     * @see #getMinIdle
     */
    public synchronized void setMinIdle(int minIdle) {
        _minIdle = minIdle;
        notifyAll();
    }

    /**
     * Returns the minimum number of objects allowed in the pool
     * before the evictor thread (if active) spawns new objects.
     * (Note no objects are created when: numActive + numIdle >= maxActive)
     *
     * @return The minimum number of objects.
     * @see #setMinIdle
     */
    public synchronized int getMinIdle() {
        return _minIdle;
    }

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * before being returned by the {@link #borrowObject}
     * method.  If the object fails to validate,
     * it will be dropped from the pool, and we will attempt
     * to borrow another.
     *
     * @see #setTestOnBorrow
     */
    public synchronized boolean getTestOnBorrow() {
        return _testOnBorrow;
    }

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * before being returned by the {@link #borrowObject}
     * method.  If the object fails to validate,
     * it will be dropped from the pool, and we will attempt
     * to borrow another.
     *
     * @see #getTestOnBorrow
     */
    public synchronized void setTestOnBorrow(boolean testOnBorrow) {
        _testOnBorrow = testOnBorrow;
    }

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * before being returned to the pool within the
     * {@link #returnObject}.
     *
     * @see #setTestOnReturn
     */
    public synchronized boolean getTestOnReturn() {
        return _testOnReturn;
    }

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * before being returned to the pool within the
     * {@link #returnObject}.
     *
     * @see #getTestOnReturn
     */
    public synchronized void setTestOnReturn(boolean testOnReturn) {
        _testOnReturn = testOnReturn;
    }

    /**
     * Returns the number of milliseconds to sleep between runs of the
     * idle object evictor thread.
     * When non-positive, no idle object evictor thread will be
     * run.
     *
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public synchronized long getTimeBetweenEvictionRunsMillis() {
        return _timeBetweenEvictionRunsMillis;
    }

    /**
     * Sets the number of milliseconds to sleep between runs of the
     * idle object evictor thread.
     * When non-positive, no idle object evictor thread will be
     * run.
     *
     * @see #getTimeBetweenEvictionRunsMillis
     */
    public synchronized void setTimeBetweenEvictionRunsMillis(long timeBetweenEvictionRunsMillis) {
        _timeBetweenEvictionRunsMillis = timeBetweenEvictionRunsMillis;
        startEvictor(_timeBetweenEvictionRunsMillis);
    }

    /**
     * Returns the max number of objects to examine during each run of the
     * idle object evictor thread (if any).
     *
     * @see #setNumTestsPerEvictionRun
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public synchronized int getNumTestsPerEvictionRun() {
        return _numTestsPerEvictionRun;
    }

    /**
     * Sets the max number of objects to examine during each run of the
     * idle object evictor thread (if any).
     * <p>
     * When a negative value is supplied, <tt>ceil({@link #getNumIdle})/abs({@link #getNumTestsPerEvictionRun})</tt>
     * tests will be run.  I.e., when the value is <i>-n</i>, roughly one <i>n</i>th of the
     * idle objects will be tested per run.
     *
     * @see #getNumTestsPerEvictionRun
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public synchronized void setNumTestsPerEvictionRun(int numTestsPerEvictionRun) {
        _numTestsPerEvictionRun = numTestsPerEvictionRun;
    }

    /**
     * Returns the minimum amount of time an object may sit idle in the pool
     * before it is eligable for eviction by the idle object evictor
     * (if any).
     *
     * @see #setMinEvictableIdleTimeMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public synchronized long getMinEvictableIdleTimeMillis() {
        return _minEvictableIdleTimeMillis;
    }

    /**
     * Sets the minimum amount of time an object may sit idle in the pool
     * before it is eligable for eviction by the idle object evictor
     * (if any).
     * When non-positive, no objects will be evicted from the pool
     * due to idle time alone.
     *
     * @see #getMinEvictableIdleTimeMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public synchronized void setMinEvictableIdleTimeMillis(long minEvictableIdleTimeMillis) {
        _minEvictableIdleTimeMillis = minEvictableIdleTimeMillis;
    }

    /**
     * Returns the minimum amount of time an object may sit idle in the pool
     * before it is eligable for eviction by the idle object evictor
     * (if any), with the extra condition that at least
     * "minIdle" amount of object remain in the pool.
     *
     * @see #setSoftMinEvictableIdleTimeMillis
     */
    public synchronized long getSoftMinEvictableIdleTimeMillis() {
        return _softMinEvictableIdleTimeMillis;
    }

    /**
     * Sets the minimum amount of time an object may sit idle in the pool
     * before it is eligable for eviction by the idle object evictor
     * (if any), with the extra condition that at least
     * "minIdle" amount of object remain in the pool.
     * When non-positive, no objects will be evicted from the pool
     * due to idle time alone.
     *
     * @see #getSoftMinEvictableIdleTimeMillis
     */
    public synchronized void setSoftMinEvictableIdleTimeMillis(long softMinEvictableIdleTimeMillis) {
        _softMinEvictableIdleTimeMillis = softMinEvictableIdleTimeMillis;
    }

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * by the idle object evictor (if any).  If an object
     * fails to validate, it will be dropped from the pool.
     *
     * @see #setTestWhileIdle
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public synchronized boolean getTestWhileIdle() {
        return _testWhileIdle;
    }

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * by the idle object evictor (if any).  If an object
     * fails to validate, it will be dropped from the pool.
     *
     * @see #getTestWhileIdle
     * @see #setTimeBetweenEvictionRunsMillis
     */
    public synchronized void setTestWhileIdle(boolean testWhileIdle) {
        _testWhileIdle = testWhileIdle;
    }

    /**
     * Sets my configuration.
     * @see GenericObjectPool.Config
     */
    public synchronized void setConfig(GenericObjectPool.Config conf) {
        setMaxIdle(conf.maxIdle);
        setMinIdle(conf.minIdle);
        setMaxActive(conf.maxActive);
        setMaxWait(conf.maxWait);
        setWhenExhaustedAction(conf.whenExhaustedAction);
        setTestOnBorrow(conf.testOnBorrow);
        setTestOnReturn(conf.testOnReturn);
        setTestWhileIdle(conf.testWhileIdle);
        setNumTestsPerEvictionRun(conf.numTestsPerEvictionRun);
        setMinEvictableIdleTimeMillis(conf.minEvictableIdleTimeMillis);
        setTimeBetweenEvictionRunsMillis(conf.timeBetweenEvictionRunsMillis);
        notifyAll();
    }

    //-- ObjectPool methods ------------------------------------------

    public synchronized Object borrowObject() throws Exception {
        assertOpen();
        long starttime = System.currentTimeMillis();
        for(;;) {
            ObjectTimestampPair pair = null;

            // if there are any sleeping, just grab one of those
            try {
                pair = (ObjectTimestampPair)(_pool.removeFirst());
            } catch(NoSuchElementException e) {
                ; /* ignored */
            }

            // otherwise
            if(null == pair) {
                // check if we can create one
                // (note we know that the num sleeping is 0, else we wouldn't be here)
                if(_maxActive < 0 || _numActive < _maxActive) {
                    // allow new object to be created
                } else {
                    // the pool is exhausted
                    switch(_whenExhaustedAction) {
                        case WHEN_EXHAUSTED_GROW:
                            // allow new object to be created
                            break;
                        case WHEN_EXHAUSTED_FAIL:
                            throw new NoSuchElementException("Pool exhausted");
                        case WHEN_EXHAUSTED_BLOCK:
                            try {
                                if(_maxWait <= 0) {
                                    wait();
                                } else {
                                    // this code may be executed again after a notify then continue cycle
                                    // so, need to calculate the amount of time to wait
                                    final long elapsed = (System.currentTimeMillis() - starttime);
                                    final long waitTime = _maxWait - elapsed;
                                    if (waitTime > 0)
                                    {
                                        wait(waitTime);
                                    }
                                }
                            } catch(InterruptedException e) {
                                // ignored
                            }
                            if(_maxWait > 0 && ((System.currentTimeMillis() - starttime) >= _maxWait)) {
                                throw new NoSuchElementException("Timeout waiting for idle object");
                            } else {
                                continue; // keep looping
                            }
                        default:
                            throw new IllegalArgumentException("WhenExhaustedAction property " + _whenExhaustedAction + " not recognized.");
                    }
                }
            }
            _numActive++;
            

            // create new object when needed
            boolean newlyCreated = false;
            if(null == pair) {
                try {
                    Object obj = _factory.makeObject();
                    pair = new ObjectTimestampPair(obj);
                    newlyCreated = true;
                } finally {
                    if (!newlyCreated) {
                        // object cannot be created
                        _numActive--;
                        notifyAll();
                    }
                }
            }

            // activate & validate the object
            try {
                _factory.activateObject(pair.value);
                if(_testOnBorrow && !_factory.validateObject(pair.value)) {
                    throw new Exception("ValidateObject failed");
                }
                _numMaxActive = _numActive > _numMaxActive?
						_numActive:_numMaxActive;
                return pair.value;
            }
            catch (Throwable e) {
                // object cannot be activated or is invalid
                _numActive--;
                notifyAll();
                try {
                    _factory.destroyObject(pair.value);
                }
                catch (Throwable e2) {
                    // cannot destroy broken object
                }
                if(newlyCreated) {
                    throw new NoSuchElementException("Could not create a validated object, cause: " + e.getMessage());
                }
                else {
                    continue; // keep looping
                }
            }
        }
    }

    public synchronized void invalidateObject(Object obj) throws Exception {
        assertOpen();
        try {
            _factory.destroyObject(obj);
        }
        finally {
            _numActive--;
            notifyAll(); // _numActive has changed
        }
    }

    public synchronized void clear() {
        assertOpen();
        for(Iterator it = _pool.iterator(); it.hasNext(); ) {
            try {
                _factory.destroyObject(((ObjectTimestampPair)(it.next())).value);
            } catch(Exception e) {
                // ignore error, keep destroying the rest
            }
            it.remove();
        }
        _pool.clear();
        notifyAll(); // num sleeping has changed
    }

    public synchronized int getNumActive() {
        assertOpen();
        return _numActive;
    }
    /**
     * 非同步方法的调用，为外部监控时使用
     */
    public int getNumActive_() {
        assertOpen();
        return _numActive;
    }
    
    
    /**
     * 获取并发最大使用链接数，记录链接池到目前为止并发使用链接的最大数目
     * @return
     */
    public int getMaxNumActive() {
        assertOpen();
        return this._numMaxActive;
    }
    /**
     * 非同步方法的调用，为外部监控时使用
     */
    public int getNumIdle_() {
        assertOpen();
        return _pool.size(); 
    }
    
    
    public synchronized int getNumIdle() {
        assertOpen();
        return _pool.size();
    }

    public synchronized void returnObject(Object obj) throws Exception {
        assertOpen();
        addObjectToPool(obj, true);
    }

    private void addObjectToPool(Object obj, boolean decrementNumActive) throws Exception {
        boolean success = true;
        if(_testOnReturn && !(_factory.validateObject(obj))) {
            success = false;
        } else {
            try {
                _factory.passivateObject(obj);
            } catch(Exception e) {
                success = false;
            }
        }

        boolean shouldDestroy = !success;

        if (decrementNumActive) {
            _numActive--;
        }
        if((_maxIdle >= 0) && (_pool.size() >= _maxIdle)) {
            shouldDestroy = true;
        } else if(success) {
            _pool.addLast(new ObjectTimestampPair(obj));
        }
        notifyAll(); // _numActive has changed

        if(shouldDestroy) {
            try {
                _factory.destroyObject(obj);
            } catch(Exception e) {
                // ignored
            }
        }
    }

    public synchronized void close() throws Exception {
        clear();
        _pool = null;
        _factory = null;
        startEvictor(-1L);
        super.close();
    }

    public synchronized void setFactory(PoolableObjectFactory factory) throws IllegalStateException {
        assertOpen();
        if(0 < getNumActive()) {
            throw new IllegalStateException("Objects are already active");
        } else {
            clear();
            _factory = factory;
        }
    }

    public synchronized void evict() throws Exception {
        assertOpen();
        if(!_pool.isEmpty()) {
            ListIterator iter;
            if (evictLastIndex < 0) {
                iter = _pool.listIterator(_pool.size());
            } else {
                iter = _pool.listIterator(evictLastIndex);
            }
            for(int i=0,m=getNumTests();i<m;i++) {
                if(!iter.hasPrevious()) {
                    iter = _pool.listIterator(_pool.size());
                }
                boolean removeObject = false;
                final ObjectTimestampPair pair = (ObjectTimestampPair)(iter.previous());
                final long idleTimeMilis = System.currentTimeMillis() - pair.tstamp;
                if ((_minEvictableIdleTimeMillis > 0)
                        && (idleTimeMilis > _minEvictableIdleTimeMillis)) {
                    removeObject = true;
                } else if ((_softMinEvictableIdleTimeMillis > 0)
                        && (idleTimeMilis > _softMinEvictableIdleTimeMillis)
                        && (getNumIdle() > getMinIdle())) {
                    removeObject = true;
                }
                if(_testWhileIdle && !removeObject) {
                    boolean active = false;
                    try {
                        _factory.activateObject(pair.value);
                        active = true;
                    } catch(Exception e) {
                        removeObject=true;
                    }
                    if(active) {
                        if(!_factory.validateObject(pair.value)) {
                            removeObject=true;
                        } else {
                            try {
                                _factory.passivateObject(pair.value);
                            } catch(Exception e) {
                                removeObject=true;
                            }
                        }
                    }
                }
                if(removeObject) {
                    try {
                        iter.remove();
                        _factory.destroyObject(pair.value);
                    } catch(Exception e) {
                        // ignored
                    }
                }
            }
            evictLastIndex = iter.previousIndex(); // resume from here
        } // if !empty
    }

    /**
     * Check to see if we are below our minimum number of objects
     * if so enough to bring us back to our minimum.
     */
    private void ensureMinIdle() throws Exception {
        // this method isn't synchronized so the
        // calculateDeficit is done at the beginning
        // as a loop limit and a second time inside the loop
        // to stop when another thread already returned the
        // needed objects
        int objectDeficit = calculateDeficit();
        for ( int j = 0 ; j < objectDeficit && calculateDeficit() > 0 ; j++ ) {
            addObject();
        }
    }

    private synchronized int calculateDeficit() {
        int objectDeficit = getMinIdle() - getNumIdle();
        if (_maxActive > 0) {
            int growLimit = Math.max(0, getMaxActive() - getNumActive() - getNumIdle());
            objectDeficit = Math.min(objectDeficit, growLimit);
        }
        return objectDeficit;
    }

    /**
     * Create an object, and place it into the pool.
     * addObject() is useful for "pre-loading" a pool with idle objects.
     */
    public synchronized void addObject() throws Exception {
        assertOpen();
        Object obj = _factory.makeObject();
        addObjectToPool(obj, false);
    }

    //--- non-public methods ----------------------------------------

    /**
     * Start the eviction thread or service, or when
     * <i>delay</i> is non-positive, stop it
     * if it is already running.
     */
    protected synchronized void startEvictor(long delay) {
        if(null != _evictor) {
            _evictor.cancel();
            _evictor = null;
        }
        if(delay > 0) {
            _evictor = new Evictor();
            EVICTION_TIMER.schedule(_evictor, delay, delay);
        }
    }

    synchronized String debugInfo() {
        StringBuffer buf = new StringBuffer();
        buf.append("Active: ").append(getNumActive()).append("\n");
        buf.append("Idle: ").append(getNumIdle()).append("\n");
        buf.append("Idle Objects:\n");
        Iterator it = _pool.iterator();
        long time = System.currentTimeMillis();
        while(it.hasNext()) {
            ObjectTimestampPair pair = (ObjectTimestampPair)(it.next());
            buf.append("\t").append(pair.value).append("\t").append(time - pair.tstamp).append("\n");
        }
        return buf.toString();
    }

    private int getNumTests() {
        if(_numTestsPerEvictionRun >= 0) {
            return Math.min(_numTestsPerEvictionRun, _pool.size());
        } else {
            return(int)(Math.ceil((double)_pool.size()/Math.abs((double)_numTestsPerEvictionRun)));
        }
    }

    //--- inner classes ----------------------------------------------

    /**
     * The idle object evictor {@link TimerTask}.
     * @see GenericObjectPool#setTimeBetweenEvictionRunsMillis
     */
    private class Evictor extends TimerTask {
        public void run() {
            try {
                evict();
            } catch(Exception e) {
                // ignored
            }
            try {
                ensureMinIdle();
            } catch(Exception e) {
                // ignored
            }
        }
    }

    /**
     * A simple "struct" encapsulating the
     * configuration information for a {@link GenericObjectPool}.
     * @see GenericObjectPool#GenericObjectPool(com.frameworkset.commons.pool.PoolableObjectFactory,com.frameworkset.commons.pool.impl.GenericObjectPool.Config)
     * @see GenericObjectPool#setConfig
     */
    public static class Config {
        public int maxIdle = GenericObjectPool.DEFAULT_MAX_IDLE;
        public int minIdle = GenericObjectPool.DEFAULT_MIN_IDLE;
        public int maxActive = GenericObjectPool.DEFAULT_MAX_ACTIVE;
        public long maxWait = GenericObjectPool.DEFAULT_MAX_WAIT;
        public byte whenExhaustedAction = GenericObjectPool.DEFAULT_WHEN_EXHAUSTED_ACTION;
        public boolean testOnBorrow = GenericObjectPool.DEFAULT_TEST_ON_BORROW;
        public boolean testOnReturn = GenericObjectPool.DEFAULT_TEST_ON_RETURN;
        public boolean testWhileIdle = GenericObjectPool.DEFAULT_TEST_WHILE_IDLE;
        public long timeBetweenEvictionRunsMillis = GenericObjectPool.DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;
        public int numTestsPerEvictionRun =  GenericObjectPool.DEFAULT_NUM_TESTS_PER_EVICTION_RUN;
        public long minEvictableIdleTimeMillis = GenericObjectPool.DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;
        public long softMinEvictableIdleTimeMillis = GenericObjectPool.DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;
    }

    //--- private attributes ---------------------------------------

    /**
     * The cap on the number of idle instances in the pool.
     * @see #setMaxIdle
     * @see #getMaxIdle
     */
    private int _maxIdle = DEFAULT_MAX_IDLE;

    /**
    * The cap on the minimum number of idle instances in the pool.
    * @see #setMinIdle
    * @see #getMinIdle
    */
    private int _minIdle = DEFAULT_MIN_IDLE;

    /**
     * The cap on the total number of active instances from the pool.
     * @see #setMaxActive
     * @see #getMaxActive
     */
    private int _maxActive = DEFAULT_MAX_ACTIVE;

    /**
     * The maximum amount of time (in millis) the
     * {@link #borrowObject} method should block before throwing
     * an exception when the pool is exhausted and the
     * {@link #getWhenExhaustedAction "when exhausted" action} is
     * {@link #WHEN_EXHAUSTED_BLOCK}.
     *
     * When less than 0, the {@link #borrowObject} method
     * may block indefinitely.
     *
     * @see #setMaxWait
     * @see #getMaxWait
     * @see #WHEN_EXHAUSTED_BLOCK
     * @see #setWhenExhaustedAction
     * @see #getWhenExhaustedAction
     */
    private long _maxWait = DEFAULT_MAX_WAIT;

    /**
     * The action to take when the {@link #borrowObject} method
     * is invoked when the pool is exhausted (the maximum number
     * of "active" objects has been reached).
     *
     * @see #WHEN_EXHAUSTED_BLOCK
     * @see #WHEN_EXHAUSTED_FAIL
     * @see #WHEN_EXHAUSTED_GROW
     * @see #DEFAULT_WHEN_EXHAUSTED_ACTION
     * @see #setWhenExhaustedAction
     * @see #getWhenExhaustedAction
     */
    private byte _whenExhaustedAction = DEFAULT_WHEN_EXHAUSTED_ACTION;

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * before being returned by the {@link #borrowObject}
     * method.  If the object fails to validate,
     * it will be dropped from the pool, and we will attempt
     * to borrow another.
     *
     * @see #setTestOnBorrow
     * @see #getTestOnBorrow
     */
    private boolean _testOnBorrow = DEFAULT_TEST_ON_BORROW;

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * before being returned to the pool within the
     * {@link #returnObject}.
     *
     * @see #getTestOnReturn
     * @see #setTestOnReturn
     */
    private boolean _testOnReturn = DEFAULT_TEST_ON_RETURN;

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * by the idle object evictor (if any).  If an object
     * fails to validate, it will be dropped from the pool.
     *
     * @see #setTestWhileIdle
     * @see #getTestWhileIdle
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    private boolean _testWhileIdle = DEFAULT_TEST_WHILE_IDLE;

    /**
     * The number of milliseconds to sleep between runs of the
     * idle object evictor thread.
     * When non-positive, no idle object evictor thread will be
     * run.
     *
     * @see #setTimeBetweenEvictionRunsMillis
     * @see #getTimeBetweenEvictionRunsMillis
     */
    private long _timeBetweenEvictionRunsMillis = DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;

    /**
     * The max number of objects to examine during each run of the
     * idle object evictor thread (if any).
     * <p>
     * When a negative value is supplied, <tt>ceil({@link #getNumIdle})/abs({@link #getNumTestsPerEvictionRun})</tt>
     * tests will be run.  I.e., when the value is <i>-n</i>, roughly one <i>n</i>th of the
     * idle objects will be tested per run.
     *
     * @see #setNumTestsPerEvictionRun
     * @see #getNumTestsPerEvictionRun
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    private int _numTestsPerEvictionRun =  DEFAULT_NUM_TESTS_PER_EVICTION_RUN;

    /**
     * The minimum amount of time an object may sit idle in the pool
     * before it is eligable for eviction by the idle object evictor
     * (if any).
     * When non-positive, no objects will be evicted from the pool
     * due to idle time alone.
     *
     * @see #setMinEvictableIdleTimeMillis
     * @see #getMinEvictableIdleTimeMillis
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    private long _minEvictableIdleTimeMillis = DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;

    /**
     * The minimum amount of time an object may sit idle in the pool
     * before it is eligable for eviction by the idle object evictor
     * (if any), with the extra condition that at least
     * "minIdle" amount of object remain in the pool.
     * When non-positive, no objects will be evicted from the pool
     * due to idle time alone.
     *
     * @see #setSoftMinEvictableIdleTimeMillis
     * @see #getSoftMinEvictableIdleTimeMillis
     */
    private long _softMinEvictableIdleTimeMillis = DEFAULT_SOFT_MIN_EVICTABLE_IDLE_TIME_MILLIS;

    /** My pool. */
    private LinkedList _pool = null;

    /** My {@link PoolableObjectFactory}. */
    private PoolableObjectFactory _factory = null;

    /**
     * The number of objects {@link #borrowObject} borrowed
     * from the pool, but not yet returned.
     */
    private int _numActive = 0;
    
    /**
     * The max number of objects {@link #borrowObject} borrowed
     * from the pool , but not yet returned ahead of now.
     */
    private int _numMaxActive = 0;

    /**
     * My idle object eviction {@link TimerTask}, if any.
     */
    private Evictor _evictor = null;

    /**
     * Position in the _pool where the _evictor last stopped.
     */
    private int evictLastIndex = -1;
}
