/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.commons.pool.impl;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.TimerTask;
  
  import org.apache.commons.pool.BaseKeyedObjectPool;
  import org.apache.commons.pool.KeyedObjectPool;
  import org.apache.commons.pool.KeyedPoolableObjectFactory;
  
  /**
   * A configurable <code>KeyedObjectPool</code> implementation.
   * <p>
   * When coupled with the appropriate {@link KeyedPoolableObjectFactory},
   * <code>GenericKeyedObjectPool</code> provides robust pooling functionality for
   * keyed objects. A <code>GenericKeyedObjectPool</code> can be viewed as a map
   * of pools, keyed on the (unique) key values provided to the
   * {@link #preparePool preparePool}, {@link #addObject addObject} or
   * {@link #borrowObject borrowObject} methods. Each time a new key value is
   * provided to one of these methods, a new pool is created under the given key
   * to be managed by the containing <code>GenericKeyedObjectPool.</code>
   * </p>
   * <p>A <code>GenericKeyedObjectPool</code> provides a number of configurable
   * parameters:</p>
   * <ul>
   *  <li>
   *    {@link #setMaxActive maxActive} controls the maximum number of objects
   *    (per key) that can allocated by the pool (checked out to client threads,
   *    or idle in the pool) at one time.  When non-positive, there is no limit
   *    to the number of objects per key. When {@link #setMaxActive maxActive} is
   *    reached, the keyed pool is said to be exhausted.  The default setting for
   *    this parameter is 8.
   *  </li>
   *  <li>
   *    {@link #setMaxTotal maxTotal} sets a global limit on the number of objects
   *    that can be in circulation (active or idle) within the combined set of
   *    pools.  When non-positive, there is no limit to the total number of
   *    objects in circulation. When {@link #setMaxTotal maxTotal} is exceeded,
   *    all keyed pools are exhausted. When <code>maxTotal</code> is set to a
   *    positive value and {@link #borrowObject borrowObject} is invoked
   *    when at the limit with no idle instances available, an attempt is made to
   *    create room by clearing the oldest 15% of the elements from the keyed
   *    pools. The default setting for this parameter is -1 (no limit).
   *  </li>
   *  <li>
   *    {@link #setMaxIdle maxIdle} controls the maximum number of objects that can
   *    sit idle in the pool (per key) at any time.  When negative, there
   *    is no limit to the number of objects that may be idle per key. The
   *    default setting for this parameter is 8.
   *  </li>
   *  <li>
   *    {@link #setWhenExhaustedAction whenExhaustedAction} specifies the
   *    behavior of the {@link #borrowObject borrowObject} method when a keyed
   *    pool is exhausted:
   *    <ul>
   *    <li>
   *      When {@link #setWhenExhaustedAction whenExhaustedAction} is
   *      {@link #WHEN_EXHAUSTED_FAIL}, {@link #borrowObject borrowObject} will throw
   *      a {@link NoSuchElementException}
   *    </li>
   *    <li>
   *      When {@link #setWhenExhaustedAction whenExhaustedAction} is
   *      {@link #WHEN_EXHAUSTED_GROW}, {@link #borrowObject borrowObject} will create a new
   *      object and return it (essentially making {@link #setMaxActive maxActive}
   *      meaningless.)
   *    </li>
   *    <li>
   *      When {@link #setWhenExhaustedAction whenExhaustedAction}
   *      is {@link #WHEN_EXHAUSTED_BLOCK}, {@link #borrowObject borrowObject} will block
   *      (invoke {@link Object#wait() wait} until a new or idle object is available.
   *      If a positive {@link #setMaxWait maxWait}
   *      value is supplied, the {@link #borrowObject borrowObject} will block for at
   *      most that many milliseconds, after which a {@link NoSuchElementException}
   *      will be thrown.  If {@link #setMaxWait maxWait} is non-positive,
  *      the {@link #borrowObject borrowObject} method will block indefinitely.
  *    </li>
  *    </ul>
  *    The default <code>whenExhaustedAction</code> setting is
  *    {@link #WHEN_EXHAUSTED_BLOCK}.
  *  </li>
  *  <li>
  *    When {@link #setTestOnBorrow testOnBorrow} is set, the pool will
  *    attempt to validate each object before it is returned from the
  *    {@link #borrowObject borrowObject} method. (Using the provided factory's
  *    {@link KeyedPoolableObjectFactory#validateObject validateObject} method.)
  *    Objects that fail to validate will be dropped from the pool, and a
  *    different object will be borrowed. The default setting for this parameter
  *    is <code>false.</code>
  *  </li>
  *  <li>
  *    When {@link #setTestOnReturn testOnReturn} is set, the pool will
  *    attempt to validate each object before it is returned to the pool in the
  *    {@link #returnObject returnObject} method. (Using the provided factory's
  *    {@link KeyedPoolableObjectFactory#validateObject validateObject}
  *    method.)  Objects that fail to validate will be dropped from the pool.
  *    The default setting for this parameter is <code>false.</code>
  *  </li>
  * </ul>
  * <p>
  * Optionally, one may configure the pool to examine and possibly evict objects
  * as they sit idle in the pool and to ensure that a minimum number of idle
  * objects is maintained for each key. This is performed by an
  * "idle object eviction" thread, which runs asynchronously. Caution should be
  * used when configuring this optional feature. Eviction runs require an
  * exclusive synchronization lock on the pool, so if they run too frequently
  * and / or incur excessive latency when creating, destroying or validating
  * object instances, performance issues may result.  The idle object eviction
  * thread may be configured using the following attributes:
  * <ul>
  *  <li>
  *   {@link #setTimeBetweenEvictionRunsMillis timeBetweenEvictionRunsMillis}
  *   indicates how long the eviction thread should sleep before "runs" of examining
  *   idle objects.  When non-positive, no eviction thread will be launched. The
  *   default setting for this parameter is -1 (i.e., by default, idle object
  *   eviction is disabled).
  *  </li>
  *  <li>
  *   {@link #setMinEvictableIdleTimeMillis minEvictableIdleTimeMillis}
  *   specifies the minimum amount of time that an object may sit idle in the
  *   pool before it is eligible for eviction due to idle time.  When
  *   non-positive, no object will be dropped from the pool due to idle time
  *   alone.  This setting has no effect unless
  *   <code>timeBetweenEvictionRunsMillis > 0.</code>  The default setting
  *   for this parameter is 30 minutes.
  *  </li>
  *  <li>
  *   {@link #setTestWhileIdle testWhileIdle} indicates whether or not idle
  *   objects should be validated using the factory's
  *   {@link KeyedPoolableObjectFactory#validateObject validateObject} method
  *   during idle object eviction runs.  Objects that fail to validate will be
  *   dropped from the pool. This setting has no effect unless
  *   <code>timeBetweenEvictionRunsMillis > 0.</code>  The default setting
  *   for this parameter is <code>false.</code>
  *  </li>
  *  <li>
  *    {@link #setMinIdle minIdle} sets a target value for the minimum number of
  *    idle objects (per key) that should always be available. If this parameter
  *    is set to a positive number and
  *    <code>timeBetweenEvictionRunsMillis > 0,</code> each time the idle object
  *    eviction thread runs, it will try to create enough idle instances so that
  *    there will be <code>minIdle</code> idle instances available under each
  *    key. This parameter is also used by {@link #preparePool preparePool}
  *    if <code>true</code> is provided as that method's
  *    <code>populateImmediately</code> parameter. The default setting for this
  *    parameter is 0.
  *  </li>
  * </ul>
  * <p>
  * The pools can be configured to behave as LIFO queues with respect to idle
  * objects - always returning the most recently used object from the pool,
  * or as FIFO queues, where borrowObject always returns the oldest object
  * in the idle object pool.
  * <ul>
  *  <li>
  *   {@link #setLifo <i>Lifo</i>}
  *   determines whether or not the pools return idle objects in
  *   last-in-first-out order. The default setting for this parameter is
  *   <code>true.</code>
  *  </li>
  * </ul>
  * <p>
  * GenericKeyedObjectPool is not usable without a {@link KeyedPoolableObjectFactory}.  A
  * non-<code>null</code> factory must be provided either as a constructor argument
  * or via a call to {@link #setFactory setFactory} before the pool is used.
  * </p>
  * <p>
  * Implementation note: To prevent possible deadlocks, care has been taken to
  * ensure that no call to a factory method will occur within a synchronization
  * block. See POOL-125 and DBCP-44 for more information.
  * </p>
  * @see GenericObjectPool
  * @author Rodney Waldhoff
  * @author Dirk Verbeeck
  * @author Sandy McArthur
  * @version $Revision: 831698 $ $Date: 2009-11-01 11:33:31 -0500 (Sun, 01 Nov 2009) $
  * @since Pool 1.0
  */
 public class GenericKeyedObjectPool extends BaseKeyedObjectPool implements KeyedObjectPool {
 
     //--- 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 idle instances (per key) in the pool.
      * @see #getMaxIdle
      * @see #setMaxIdle
      */
     public static final int DEFAULT_MAX_IDLE  = 8;
 
     /**
      * The default cap on the total number of active instances (per key)
      * from the pool.
      * @see #getMaxActive
      * @see #setMaxActive
      */
     public static final int DEFAULT_MAX_ACTIVE  = 8;
 
     /**
      * The default cap on the the overall maximum number of objects that can
      * exist at one time.
      * @see #getMaxTotal
      * @see #setMaxTotal
      */
     public static final int DEFAULT_MAX_TOTAL  = -1;
 
     /**
      * 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 milliseconds) 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 minimum level of idle objects in the pool.
      * @since Pool 1.3
      * @see #setMinIdle
      * @see #getMinIdle
      */
     public static final int DEFAULT_MIN_IDLE = 0;
 
     /**
      * The default LIFO status. True means that borrowObject returns the
      * most recently used ("last in") idle object in a pool (if there are
      * idle instances available).  False means that pools behave as FIFO
      * queues - objects are taken from idle object pools in the order that
      * they are returned.
      * @see #setLifo
      */
     public static final boolean DEFAULT_LIFO = true;
 
     //--- constructors -----------------------------------------------
 
     /**
      * Create a new <code>GenericKeyedObjectPool</code> with no factory.
      *
      * @see #GenericKeyedObjectPool(KeyedPoolableObjectFactory)
      * @see #setFactory(KeyedPoolableObjectFactory)
      */
     public GenericKeyedObjectPool() {
         this(null, DEFAULT_MAX_ACTIVE, DEFAULT_WHEN_EXHAUSTED_ACTION, DEFAULT_MAX_WAIT, DEFAULT_MAX_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 <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy
      * objects if not <code>null</code>
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory) {
         this(factory, DEFAULT_MAX_ACTIVE, DEFAULT_WHEN_EXHAUSTED_ACTION, DEFAULT_MAX_WAIT, DEFAULT_MAX_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 <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @param config a non-<code>null</code> {@link GenericKeyedObjectPool.Config} describing the configuration
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, GenericKeyedObjectPool.Config config) {
         this(factory, config.maxActive, config.whenExhaustedAction, config.maxWait, config.maxIdle, config.maxTotal,
                 config.minIdle, config.testOnBorrow, config.testOnReturn, config.timeBetweenEvictionRunsMillis,
                 config.numTestsPerEvictionRun, config.minEvictableIdleTimeMillis, config.testWhileIdle, config.lifo);
     }
 
     /**
      * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive) {
         this(factory,maxActive, DEFAULT_WHEN_EXHAUSTED_ACTION, DEFAULT_MAX_WAIT, DEFAULT_MAX_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 <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @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 and
      *  <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
             long maxWait) {
         this(factory, maxActive, whenExhaustedAction, maxWait, DEFAULT_MAX_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 <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
      * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
      * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
      * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
      * @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})
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
             long maxWait, boolean testOnBorrow, boolean testOnReturn) {
         this(factory, maxActive, whenExhaustedAction, maxWait, DEFAULT_MAX_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 <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @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 and
      * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
      * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
             long maxWait, int maxIdle) {
         this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, 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 <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @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 and
      * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #getMaxWait})
      * @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})
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
             long maxWait, int maxIdle, boolean testOnBorrow, boolean testOnReturn) {
         this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, 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 <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @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 and
      * <code>whenExhaustedAction</code> 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 eligible for eviction (see {@link #setMinEvictableIdleTimeMillis})
      * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any
      * (see {@link #setTestWhileIdle})
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory 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, GenericKeyedObjectPool.DEFAULT_MAX_TOTAL,
                 testOnBorrow, testOnReturn, timeBetweenEvictionRunsMillis, numTestsPerEvictionRun,
                 minEvictableIdleTimeMillis, testWhileIdle);
     }
 
     /**
      * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @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 and
      * <code>whenExhaustedAction</code> 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 maxTotal the maximum number of objects that can exists at one time (see {@link #setMaxTotal})
      * @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 eligible for eviction (see {@link #setMinEvictableIdleTimeMillis})
      * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any
      * (see {@link #setTestWhileIdle})
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
             long maxWait, int maxIdle, int maxTotal, boolean testOnBorrow, boolean testOnReturn,
             long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis,
             boolean testWhileIdle) {
         this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, maxTotal,
                 GenericKeyedObjectPool.DEFAULT_MIN_IDLE, testOnBorrow, testOnReturn, timeBetweenEvictionRunsMillis,
                 numTestsPerEvictionRun, minEvictableIdleTimeMillis, testWhileIdle);
     }
 
     /**
      * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @param maxActive the maximum number of objects that can be borrowed 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 and
      * <code>whenExhaustedAction</code> 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 maxTotal the maximum number of objects that can exists at one time (see {@link #setMaxTotal})
      * @param minIdle the minimum number of idle objects to have in the pool at any one time (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 eligible for eviction (see {@link #setMinEvictableIdleTimeMillis})
      * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any
      * (see {@link #setTestWhileIdle})
      * @since Pool 1.3
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
             long maxWait, int maxIdle, int maxTotal, int minIdle, boolean testOnBorrow, boolean testOnReturn,
             long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis,
             boolean testWhileIdle) {
         this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, maxTotal, minIdle, testOnBorrow, testOnReturn,
                 timeBetweenEvictionRunsMillis, numTestsPerEvictionRun, minEvictableIdleTimeMillis, testWhileIdle,
                 DEFAULT_LIFO);
     }
 
     /**
      * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
      * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
      * if not <code>null</code>
      * @param maxActive the maximum number of objects that can be borrowed 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 and
      * <code>whenExhaustedAction</code> 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 maxTotal the maximum number of objects that can exists at one time (see {@link #setMaxTotal})
      * @param minIdle the minimum number of idle objects to have in the pool at any one time (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 eligible for eviction (see {@link #setMinEvictableIdleTimeMillis})
      * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any
      * (see {@link #setTestWhileIdle})
      * @param lifo whether or not the pools behave as LIFO (last in first out) queues (see {@link #setLifo})
      * @since Pool 1.4
      */
     public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
             long maxWait, int maxIdle, int maxTotal, int minIdle, boolean testOnBorrow, boolean testOnReturn,
             long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis,
             boolean testWhileIdle, boolean lifo) {
         _factory = factory;
         _maxActive = maxActive;
         _lifo = lifo;
         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;
         _maxTotal = maxTotal;
         _minIdle = minIdle;
         _testOnBorrow = testOnBorrow;
         _testOnReturn = testOnReturn;
         _timeBetweenEvictionRunsMillis = timeBetweenEvictionRunsMillis;
         _numTestsPerEvictionRun = numTestsPerEvictionRun;
         _minEvictableIdleTimeMillis = minEvictableIdleTimeMillis;
         _testWhileIdle = testWhileIdle;
 
         _poolMap = new HashMap();
         _poolList = new CursorableLinkedList();
 
         startEvictor(_timeBetweenEvictionRunsMillis);
     }
 
     //--- public methods ---------------------------------------------
 
     //--- configuration methods --------------------------------------
 
     /**
      * Returns the cap on the number of object instances allocated by the pool
      * (checked out or idle),  per key.
      * A negative value indicates no limit.
      *
      * @return the cap on the number of active instances per key.
      * @see #setMaxActive
      */
     public synchronized int getMaxActive() {
         return _maxActive;
     }
 
     /**
      * Sets the cap on the number of object instances managed by the pool per key.
      * @param maxActive The cap on the number of object instances per key.
      * Use a negative value for no limit.
      *
      * @see #getMaxActive
      */
     public synchronized void setMaxActive(int maxActive) {
         _maxActive = maxActive;
         allocate();
     }
 
     /**
      * Returns the overall maximum number of objects (across pools) that can
      * exist at one time. A negative value indicates no limit.
      * @return the maximum number of instances in circulation at one time.
      * @see #setMaxTotal
      */
     public synchronized int getMaxTotal() {
         return _maxTotal;
     }
 
     /**
      * Sets the cap on the total number of instances from all pools combined.
      * When <code>maxTotal</code> is set to a
      * positive value and {@link #borrowObject borrowObject} is invoked
      * when at the limit with no idle instances available, an attempt is made to
      * create room by clearing the oldest 15% of the elements from the keyed
      * pools.
      *
      * @param maxTotal The cap on the total number of instances across pools.
      * Use a negative value for no limit.
      * @see #getMaxTotal
      */
     public synchronized void setMaxTotal(int maxTotal) {
         _maxTotal = maxTotal;
         allocate();
     }
 
     /**
      * 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;
                 allocate();
                 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 or equal to 0, the {@link #borrowObject} method
      * may block indefinitely.
      *
      * @return the maximum number of milliseconds borrowObject will block.
      * @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 or equal to 0, the {@link #borrowObject} method
      * may block indefinitely.
      *
      * @param maxWait the maximum number of milliseconds borrowObject will block or negative for indefinitely.
      * @see #getMaxWait
      * @see #setWhenExhaustedAction
      * @see #WHEN_EXHAUSTED_BLOCK
      */
     public synchronized void setMaxWait(long maxWait) {
         _maxWait = maxWait;
     }
 
     /**
      * Returns the cap on the number of "idle" instances per key.
      * @return the maximum number of "idle" instances that can be held
      * in a given keyed pool.
      * @see #setMaxIdle
      */
     public synchronized int getMaxIdle() {
         return _maxIdle;
     }
 
     /**
      * Sets the cap on the number of "idle" instances in the pool.
      * If maxIdle is set too low on heavily loaded systems it is possible you
      * will see objects being destroyed and almost immediately new objects
      * being created. This is a result of the active threads momentarily
      * returning objects faster than they are requesting them them, causing the
      * number of idle objects to rise above maxIdle. The best value for maxIdle
      * for heavily loaded system will vary but the default is a good starting
      * point.
      * @param maxIdle the maximum number of "idle" instances that can be held
      * in a given keyed pool. Use a negative value for no limit.
      * @see #getMaxIdle
      * @see #DEFAULT_MAX_IDLE
      */
     public synchronized void setMaxIdle(int maxIdle) {
         _maxIdle = maxIdle;
         allocate();
     }
 
     /**
      * Sets the minimum number of idle objects to maintain in each of the keyed
      * pools. This setting has no effect unless
      * <code>timeBetweenEvictionRunsMillis > 0</code> and attempts to ensure
      * that each pool has the required minimum number of instances are only
      * made during idle object eviction runs.
      * @param poolSize - The minimum size of the each keyed pool
      * @since Pool 1.3
      * @see #getMinIdle
      * @see #setTimeBetweenEvictionRunsMillis
      */
     public synchronized void setMinIdle(int poolSize) {
         _minIdle = poolSize;
     }
 
     /**
      * Returns the minimum number of idle objects to maintain in each of the keyed
      * pools. This setting has no effect unless
      * <code>timeBetweenEvictionRunsMillis > 0</code> and attempts to ensure
      * that each pool has the required minimum number of instances are only
      * made during idle object eviction runs.
      * @return minimum size of the each keyed pool
      * @since Pool 1.3
      * @see #setTimeBetweenEvictionRunsMillis
      */
     public synchronized int getMinIdle() {
         return _minIdle;
     }
 
     /**
      * When <code>true</code>, objects will be
      * {@link org.apache.commons.pool.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.
      *
      * @return <code>true</code> if objects are validated before being borrowed.
      * @see #setTestOnBorrow
      */
     public boolean getTestOnBorrow() {
         return _testOnBorrow;
     }
 
     /**
      * When <code>true</code>, objects will be
      * {@link org.apache.commons.pool.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.
      *
      * @param testOnBorrow whether object should be validated before being returned by borrowObject.
      * @see #getTestOnBorrow
      */
     public void setTestOnBorrow(boolean testOnBorrow) {
         _testOnBorrow = testOnBorrow;
     }
 
     /**
      * When <code>true</code>, objects will be
      * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
      * before being returned to the pool within the
      * {@link #returnObject}.
      *
      * @return <code>true</code> when objects will be validated before being returned.
      * @see #setTestOnReturn
      */
     public boolean getTestOnReturn() {
         return _testOnReturn;
     }
 
     /**
      * When <code>true</code>, objects will be
      * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
      * before being returned to the pool within the
      * {@link #returnObject}.
      *
      * @param testOnReturn <code>true</code> so objects will be validated before being returned.
      * @see #getTestOnReturn
      */
     public 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.
      *
      * @return milliseconds to sleep between evictor runs.
      * @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.
      *
      * @param timeBetweenEvictionRunsMillis milliseconds to sleep between evictor runs.
      * @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).
      *
      * @return number of objects to examine each eviction run.
      * @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, 
      * <code>ceil({@link #getNumIdle()})/abs({@link #getNumTestsPerEvictionRun})</code>
      * tests will be run.  I.e., when the value is <code>-n</code>, roughly one <code>n</code>th of the
      * idle objects will be tested per run.  When the value is positive, the number of tests
      * actually performed in each run will be the minimum of this value and the number of instances
      * idle in the pools.
      *
      * @param numTestsPerEvictionRun number of objects to examine each eviction run.
      * @see #setNumTestsPerEvictionRun
      * @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 eligible for eviction by the idle object evictor
      * (if any).
      *
      * @return minimum amount of time an object may sit idle in the pool before it is eligible for eviction.
      * @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 eligible 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.
      *
      * @param minEvictableIdleTimeMillis minimum amount of time an object may sit idle in the pool before
      * it is eligible for eviction.
      * @see #getMinEvictableIdleTimeMillis
      * @see #setTimeBetweenEvictionRunsMillis
      */
     public synchronized void setMinEvictableIdleTimeMillis(long minEvictableIdleTimeMillis) {
         _minEvictableIdleTimeMillis = minEvictableIdleTimeMillis;
     }
 
     /**
      * When <code>true</code>, objects will be
      * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
      * by the idle object evictor (if any).  If an object
      * fails to validate, it will be dropped from the pool.
      *
      * @return <code>true</code> when objects are validated when borrowed.
      * @see #setTestWhileIdle
      * @see #setTimeBetweenEvictionRunsMillis
      */
     public synchronized boolean getTestWhileIdle() {
         return _testWhileIdle;
     }
 
     /**
      * When <code>true</code>, objects will be
      * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
      * by the idle object evictor (if any).  If an object
      * fails to validate, it will be dropped from the pool.
      *
      * @param testWhileIdle <code>true</code> so objects are validated when borrowed.
      * @see #getTestWhileIdle
      * @see #setTimeBetweenEvictionRunsMillis
      */
     public synchronized void setTestWhileIdle(boolean testWhileIdle) {
         _testWhileIdle = testWhileIdle;
     }
 
     /**
      * Sets the configuration.
      * @param conf the new configuration to use.
      * @see GenericKeyedObjectPool.Config
      */
     public synchronized void setConfig(GenericKeyedObjectPool.Config conf) {
         setMaxIdle(conf.maxIdle);
         setMaxActive(conf.maxActive);
         setMaxTotal(conf.maxTotal);
         setMinIdle(conf.minIdle);
         setMaxWait(conf.maxWait);
         setWhenExhaustedAction(conf.whenExhaustedAction);
         setTestOnBorrow(conf.testOnBorrow);
         setTestOnReturn(conf.testOnReturn);
         setTestWhileIdle(conf.testWhileIdle);
         setNumTestsPerEvictionRun(conf.numTestsPerEvictionRun);
         setMinEvictableIdleTimeMillis(conf.minEvictableIdleTimeMillis);
         setTimeBetweenEvictionRunsMillis(conf.timeBetweenEvictionRunsMillis);
     }
 
     /**
      * Whether or not the idle object pools act as LIFO queues. True means
      * that borrowObject returns the most recently used ("last in") idle object
      * in a pool (if there are idle instances available).  False means that
      * the pools behave as FIFO queues - objects are taken from idle object
      * pools in the order that they are returned.
      *
      * @return <code>true</code> if the pools are configured to act as LIFO queues
      * @since 1.4
      */
      public synchronized boolean getLifo() {
          return _lifo;
      }
 
      /**
       * Sets the LIFO property of the pools. True means that borrowObject returns
       * the most recently used ("last in") idle object in a pool (if there are
       * idle instances available).  False means that the pools behave as FIFO
       * queues - objects are taken from idle object pools in the order that
       * they are returned.
       *
       * @param lifo the new value for the lifo property
       * @since 1.4
       */
      public synchronized void setLifo(boolean lifo) {
          this._lifo = lifo;
      }
 
     //-- ObjectPool methods ------------------------------------------
 
     /**
      * <p>Borrows an object from the keyed pool associated with the given key.</p>
      * 
      * <p>If there is an idle instance available in the pool associated with the given key, then
      * either the most-recently returned (if {@link #getLifo() lifo} == true) or "oldest" (lifo == false)
      * instance sitting idle in the pool will be activated and returned.  If activation fails, or
      * {@link #getTestOnBorrow() testOnBorrow} is set to true and validation fails, the instance is destroyed and the
      * next available instance is examined.  This continues until either a valid instance is returned or there
      * are no more idle instances available.</p>
      * 
      * <p>If there are no idle instances available in the pool associated with the given key, behavior
      * depends on the {@link #getMaxActive() maxActive}, {@link #getMaxTotal() maxTotal}, and (if applicable)
      * {@link #getWhenExhaustedAction() whenExhaustedAction} and {@link #getMaxWait() maxWait} properties. If the
      * number of instances checked out from the pool under the given key is less than <code>maxActive</code> and
      * the total number of instances in circulation (under all keys) is less than <code>maxTotal</code>, a new instance
      * is created, activated and (if applicable) validated and returned to the caller.</p>
      * 
      * <p>If the associated keyed pool is exhausted (no available idle instances and no capacity to create new ones),
      * this method will either block ({@link #WHEN_EXHAUSTED_BLOCK}), throw a <code>NoSuchElementException</code>
      * ({@link #WHEN_EXHAUSTED_FAIL}), or grow ({@link #WHEN_EXHAUSTED_GROW} - ignoring maxActive, maxTotal properties).
      * The length of time that this method will block when <code>whenExhaustedAction == WHEN_EXHAUSTED_BLOCK</code>
      * is determined by the {@link #getMaxWait() maxWait} property.</p>
      * 
      * <p>When the pool is exhausted, multiple calling threads may be simultaneously blocked waiting for instances
      * to become available.  As of pool 1.5, a "fairness" algorithm has been implemented to ensure that threads receive
      * available instances in request arrival order.</p>
      * 
      * @param key pool key
      * @return object instance from the keyed pool
      * @throws NoSuchElementException if a keyed object instance cannot be returned.
      */
      public Object borrowObject(Object key) throws Exception {
         long starttime = System.currentTimeMillis();
         Latch latch = new Latch(key);
         byte whenExhaustedAction;
         long maxWait;
         synchronized (this) {
             // Get local copy of current config. Can't sync when used later as
             // it can result in a deadlock. Has the added advantage that config
             // is consistent for entire method execution
             whenExhaustedAction = _whenExhaustedAction;
             maxWait = _maxWait;
 
             // Add this request to the queue
             _allocationQueue.add(latch);
 
             // Work the allocation queue, allocating idle instances and
             // instance creation permits in request arrival order
             allocate();
         }
 
         for(;;) {
             synchronized (this) {
                 assertOpen();
             }
             // If no object was allocated
             if (null == latch.getPair()) {
                 // Check to see if we were allowed to create one
                 if (latch.mayCreate()) {
                     // allow new object to be created
                 } else {
                     // the pool is exhausted
                     switch(whenExhaustedAction) {
                         case WHEN_EXHAUSTED_GROW:
                             // allow new object to be created
                             synchronized (this) {
                                 // Make sure another thread didn't allocate us an object
                                 // or permit a new object to be created
                                 if (latch.getPair() == null && !latch.mayCreate()) {
                                     _allocationQueue.remove(latch);
                                     latch.getPool().incrementInternalProcessingCount();
                                 }
                             }
                         break;
                         case WHEN_EXHAUSTED_FAIL:
                             synchronized (this) {
                                 // Make sure allocate hasn't already assigned an object
                                 // in a different thread or permitted a new object to be created
                                 if (latch.getPair() != null || latch.mayCreate()) {
                                     break;
                                 }
                                 _allocationQueue.remove(latch);
                             }
                             throw new NoSuchElementException("Pool exhausted");
                         case WHEN_EXHAUSTED_BLOCK:
                             try {
                                 synchronized (latch) {
                                     // Before we wait, make sure another thread didn't allocate us an object
                                     // or permit a new object to be created
                                     if (latch.getPair() == null && !latch.mayCreate()) {
                                         if (maxWait <= 0) {
                                             latch.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)
                                             {
                                                 latch.wait(waitTime);
                                             }
                                         }
                                     } else {
                                         break;
                                     }
                                 }
                             } catch(InterruptedException e) {
                                 Thread.currentThread().interrupt();
                                 throw e;
                                 }
                             if (maxWait > 0 && ((System.currentTimeMillis() - starttime) >= maxWait)) {
                                 synchronized (this) {
                                     // Make sure allocate hasn't already assigned an object
                                     // in a different thread or permitted a new object to be created
                                     if (latch.getPair() == null && !latch.mayCreate()) {
                                         _allocationQueue.remove(latch);
                                     } else {
                                         break;
                                     }
                                 }
                                 throw new NoSuchElementException("Timeout waiting for idle object");
                             } else {
                                 continue; // keep looping
                             }
                         default:
                             throw new IllegalArgumentException("whenExhaustedAction " + whenExhaustedAction +
                                     " not recognized.");
                     }
                 }
             }
 
             boolean newlyCreated = false;
             if (null == latch.getPair()) {
                 try {
                     Object obj = _factory.makeObject(key);
                     latch.setPair(new ObjectTimestampPair(obj));
                     newlyCreated = true;
                 } finally {
                     if (!newlyCreated) {
                         // object cannot be created
                         synchronized (this) {
                             latch.getPool().decrementInternalProcessingCount();
                             // No need to reset latch - about to throw exception
                             allocate();
                         }
                     }
                 }
             }
 
             // activate & validate the object
             try {
                 _factory.activateObject(key, latch.getPair().value);
                 if (_testOnBorrow && !_factory.validateObject(key, latch.getPair().value)) {
                     throw new Exception("ValidateObject failed");
                 }
                 synchronized (this) {
                     latch.getPool().decrementInternalProcessingCount();
                     latch.getPool().incrementActiveCount();
                 }
                 return latch.getPair().value;
             } catch (Throwable e) {
                 // object cannot be activated or is invalid
                 try {
                     _factory.destroyObject(key, latch.getPair().value);
                 } catch (Throwable e2) {
                     // cannot destroy broken object
                 }
                 synchronized (this) {
                     latch.getPool().decrementInternalProcessingCount();
                     if (!newlyCreated) {
                         latch.reset();
                         _allocationQueue.add(0, latch);
                     }
                     allocate();
                 }
                 if (newlyCreated) {
                     throw new NoSuchElementException(
                        "Could not create a validated object, cause: " +
                             e.getMessage());
                 }
                 else {
                     continue; // keep looping
                 }
             }
         }
     }
 
     /**
      * Allocate available instances to latches in the allocation queue.  Then
      * set _mayCreate to true for as many additional latches remaining in queue
      * as _maxActive allows for each key.
      */
     private void allocate() {
         boolean clearOldest = false;
 
         synchronized (this) {
             if (isClosed()) return;
             
             Iterator allocationQueueIter = _allocationQueue.iterator();
             
             while (allocationQueueIter.hasNext()) {
                 // First use any objects in the pool to clear the queue
                 Latch latch = (Latch) allocationQueueIter.next();
                 ObjectQueue pool = (ObjectQueue)(_poolMap.get(latch.getkey()));
                 if (null == pool) {
                     pool = new ObjectQueue();
                     _poolMap.put(latch.getkey(), pool);
                     _poolList.add(latch.getkey());
                 }
                 latch.setPool(pool);
                 if (!pool.queue.isEmpty()) {
                     allocationQueueIter.remove();
                     latch.setPair(
                             (ObjectTimestampPair) pool.queue.removeFirst());
                     pool.incrementInternalProcessingCount();
                     _totalIdle--;
                     synchronized (latch) {
                         latch.notify();
                     }
                     // Next item in queue
                     continue;
                 }
 
                 // If there is a totalMaxActive and we are at the limit then
                 // we have to make room
                 if ((_maxTotal > 0) &&
                         (_totalActive + _totalIdle + _totalInternalProcessing >= _maxTotal)) {
                     clearOldest = true;
                     break;
                 }
 
                 // Second utilise any spare capacity to create new objects
                 if ((_maxActive < 0 || pool.activeCount + pool.internalProcessingCount < _maxActive) &&
                         (_maxTotal < 0 || _totalActive + _totalIdle + _totalInternalProcessing < _maxTotal)) {
                     // allow new object to be created
                     allocationQueueIter.remove();
                     latch.setMayCreate(true);
                     pool.incrementInternalProcessingCount();
                     synchronized (latch) {
                         latch.notify();
                     }
                     // Next item in queue
                     continue;
                 }
 
                 // If there is no per-key limit and we reach this point we
                 // must have allocated all the objects we possibly can and there
                 // is no point looking at the rest of the allocation queue
                 if (_maxActive < 0) {
                     break;
                 }
             }
         }
         
         if (clearOldest) {
             /* Clear oldest calls factory methods so it must be called from
              * outside the sync block.
              * It also needs to be outside the sync block as it calls
              * allocate(). If called inside the sync block, the call to
              * allocate() would be able to enter the sync block (since the
              * thread already has the lock) which may have unexpected,
              * unpleasant results.
              */
             clearOldest();
         }
     }
     
     /**
      * Clears any objects sitting idle in the pool by removing them from the
      * idle instance pool and then invoking the configured 
      * {@link KeyedPoolableObjectFactory#destroyObject(Object, Object)} method on
      * each idle instance.
      *  
      * <p> Implementation notes:
      * <ul><li>This method does not destroy or effect in any way instances that are
      * checked out when it is invoked.</li>
      * <li>Invoking this method does not prevent objects being
      * returned to the idle instance pool, even during its execution. It locks
      * the pool only during instance removal. Additional instances may be returned
      * while removed items are being destroyed.</li></ul></p>
      */
     public void clear() {
         Map toDestroy = new HashMap();
         synchronized (this) {
             for (Iterator it = _poolMap.keySet().iterator(); it.hasNext();) {
                 Object key = it.next();
                 ObjectQueue pool = (ObjectQueue)_poolMap.get(key);
                 // Copy objects to new list so pool.queue can be cleared inside
                 // the sync
                 List objects = new ArrayList();
                 objects.addAll(pool.queue);
                 toDestroy.put(key, objects);
                 it.remove();
                 _poolList.remove(key);
                 _totalIdle = _totalIdle - pool.queue.size();
                 _totalInternalProcessing =
                     _totalInternalProcessing + pool.queue.size();
                 pool.queue.clear();
             }
         }
         destroy(toDestroy);
     }
 
     /**
      * Clears oldest 15% of objects in pool.  The method sorts the
      * objects into a TreeMap and then iterates the first 15% for removal.
      * 
      * @since Pool 1.3
      */
     public void clearOldest() {
         // Map of objects to destroy my key
         final Map toDestroy = new HashMap();
 
         // build sorted map of idle objects
         final Map map = new TreeMap();
         synchronized (this) {
             for (Iterator keyiter = _poolMap.keySet().iterator(); keyiter.hasNext();) {
                 final Object key = keyiter.next();
                 final CursorableLinkedList list = ((ObjectQueue)_poolMap.get(key)).queue;
                 for (Iterator it = list.iterator(); it.hasNext();) {
                     // each item into the map uses the objectimestamppair object
                     // as the key.  It then gets sorted based on the timstamp field
                     // each value in the map is the parent list it belongs in.
                     map.put(it.next(), key);
                 }
             }
 
             // Now iterate created map and kill the first 15% plus one to account for zero
             Set setPairKeys = map.entrySet();
             int itemsToRemove = ((int) (map.size() * 0.15)) + 1;
 
             Iterator iter = setPairKeys.iterator();
             while (iter.hasNext() && itemsToRemove > 0) {
                 Map.Entry entry = (Map.Entry) iter.next();
                 // kind of backwards on naming.  In the map, each key is the objecttimestamppair
                 // because it has the ordering with the timestamp value.  Each value that the
                 // key references is the key of the list it belongs to.
                 Object key = entry.getValue();
                 ObjectTimestampPair pairTimeStamp = (ObjectTimestampPair) entry.getKey();
                 final CursorableLinkedList list =
                     ((ObjectQueue)(_poolMap.get(key))).queue;
                 list.remove(pairTimeStamp);
 
                 if (toDestroy.containsKey(key)) {
                     ((List)toDestroy.get(key)).add(pairTimeStamp);
                 } else {
                     List listForKey = new ArrayList();
                     listForKey.add(pairTimeStamp);
                     toDestroy.put(key, listForKey);
                 }
                 // if that was the last object for that key, drop that pool
                 if (list.isEmpty()) {
                     _poolMap.remove(key);
                     _poolList.remove(key);
                 }
                 _totalIdle--;
                 _totalInternalProcessing++;
                 itemsToRemove--;
             }
 
         }
         destroy(toDestroy);
     }
 
     /**
      * Clears the specified pool, removing all pooled instances corresponding to the given <code>key</code>.
      *
      * @param key the key to clear
      */
     public void clear(Object key) {
         Map toDestroy = new HashMap();
 
         final ObjectQueue pool;
         synchronized (this) {
             pool = (ObjectQueue)(_poolMap.remove(key));
             if (pool == null) {
                 return;
             } else {
                 _poolList.remove(key);
             }
             // Copy objects to new list so pool.queue can be cleared inside
             // the sync
             List objects = new ArrayList();
             objects.addAll(pool.queue);
             toDestroy.put(key, objects);
             _totalIdle = _totalIdle - pool.queue.size();
             _totalInternalProcessing =
                 _totalInternalProcessing + pool.queue.size();
             pool.queue.clear();
         }
         destroy(toDestroy);
     }
 
     /**
      * Assuming Map<Object,Collection<ObjectTimestampPair>>, destroy all
      * ObjectTimestampPair.value
      * 
      * @param m Map containing keyed pools to clear
      */
     private void destroy(Map m) {
         for (Iterator keys = m.keySet().iterator(); keys.hasNext();) {
             Object key = keys.next();
             Collection c = (Collection) m.get(key);
             for (Iterator it = c.iterator(); it.hasNext();) {
                 try {
                     _factory.destroyObject(
                             key,((ObjectTimestampPair)(it.next())).value);
                 } catch(Exception e) {
                     // ignore error, keep destroying the rest
                 } finally {
                     synchronized(this) {
                         _totalInternalProcessing--;
                         allocate();
                     }
                 }
             }
 
         }
     }
 
     /**
      * Returns the total number of instances current borrowed from this pool but not yet returned.
      *
      * @return the total number of instances currently borrowed from this pool
      */
     public synchronized int getNumActive() {
         return _totalActive;
     }
 
     /**
      * Returns the total number of instances currently idle in this pool.
      *
      * @return the total number of instances currently idle in this pool
      */
     public synchronized int getNumIdle() {
         return _totalIdle;
     }
 
     /**
      * Returns the number of instances currently borrowed from but not yet returned
      * to the pool corresponding to the given <code>key</code>.
      *
      * @param key the key to query
      * @return the number of instances corresponding to the given <code>key</code> currently borrowed in this pool
      */
     public synchronized int getNumActive(Object key) {
         final ObjectQueue pool = (ObjectQueue)(_poolMap.get(key));
         return pool != null ? pool.activeCount : 0;
     }
 
     /**
      * Returns the number of instances corresponding to the given <code>key</code> currently idle in this pool.
      *
      * @param key the key to query
      * @return the number of instances corresponding to the given <code>key</code> currently idle in this pool
      */
     public synchronized int getNumIdle(Object key) {
         final ObjectQueue pool = (ObjectQueue)(_poolMap.get(key));
         return pool != null ? pool.queue.size() : 0;
     }
 
     /**
      * <p>Returns an object to a keyed pool.</p>
      * 
      * <p>For the pool to function correctly, the object instance <strong>must</strong> have been borrowed
      * from the pool (under the same key) and not yet returned. Repeated <code>returnObject</code> calls on
      * the same object/key pair (with no <code>borrowObject</code> calls in between) will result in multiple
      * references to the object in the idle instance pool.</p>
      * 
      * <p>If {@link #getMaxIdle() maxIdle} is set to a positive value and the number of idle instances under the given
      * key has reached this value, the returning instance is destroyed.</p>
      * 
      * <p>If {@link #getTestOnReturn() testOnReturn} == true, the returning instance is validated before being returned
      * to the idle instance pool under the given key.  In this case, if validation fails, the instance is destroyed.</p>
      * 
      * @param key pool key
      * @param obj instance to return to the keyed pool
      * @throws Exception
      */
     public void returnObject(Object key, Object obj) throws Exception {
         try {
             addObjectToPool(key, obj, true);
         } catch (Exception e) {
             if (_factory != null) {
                 try {
                     _factory.destroyObject(key, obj);
                 } catch (Exception e2) {
                     // swallowed
                 }
                 // TODO: Correctness here depends on control in addObjectToPool.
                 // These two methods should be refactored, removing the
                 // "behavior flag", decrementNumActive, from addObjectToPool.
                 ObjectQueue pool = (ObjectQueue) (_poolMap.get(key));
                 if (pool != null) {
                     synchronized(this) {
                         pool.decrementActiveCount();
                         allocate();
                     }
                 }
             }
         }
     }
 
     /**
      * <p>Adds an object to the keyed pool.</p>
      * 
      * <p>Validates the object if testOnReturn == true and passivates it before returning it to the pool.
      * if validation or passivation fails, or maxIdle is set and there is no room in the pool, the instance
      * is destroyed.</p>
      * 
      * <p>Calls {@link #allocate()} on successful completion</p>
      * 
      * @param key pool key
      * @param obj instance to add to the keyed pool
      * @param decrementNumActive whether or not to decrement the active count associated with the keyed pool
      * @throws Exception
      */
     private void addObjectToPool(Object key, Object obj,
             boolean decrementNumActive) throws Exception {
 
         // if we need to validate this object, do so
         boolean success = true; // whether or not this object passed validation
         if (_testOnReturn && !_factory.validateObject(key, obj)) {
             success = false;
         } else {
             _factory.passivateObject(key, obj);
         }
 
         boolean shouldDestroy = !success;
         ObjectQueue pool;
 
         // Add instance to pool if there is room and it has passed validation
         // (if testOnreturn is set)
         synchronized (this) {
             // grab the pool (list) of objects associated with the given key
             pool = (ObjectQueue) (_poolMap.get(key));
             // if it doesn't exist, create it
             if (null == pool) {
                 pool = new ObjectQueue();
                 _poolMap.put(key, pool);
                 _poolList.add(key);
             }
             if (isClosed()) {
                 shouldDestroy = true;
             } else {
                 // if there's no space in the pool, flag the object for destruction
                 // else if we passivated successfully, return it to the pool
                 if (_maxIdle >= 0 && (pool.queue.size() >= _maxIdle)) {
                     shouldDestroy = true;
                 } else if (success) {
                     // borrowObject always takes the first element from the queue,
                     // so for LIFO, push on top, FIFO add to end
                     if (_lifo) {
                         pool.queue.addFirst(new ObjectTimestampPair(obj));
                     } else {
                         pool.queue.addLast(new ObjectTimestampPair(obj));
                     }
                     _totalIdle++;
                     if (decrementNumActive) {
                         pool.decrementActiveCount();
                     }
                     allocate();
                 }
             }
         }
 
         // Destroy the instance if necessary
         if (shouldDestroy) {
             try {
                 _factory.destroyObject(key, obj);
             } catch(Exception e) {
                 // ignored?
             }
             // Decrement active count *after* destroy if applicable
             if (decrementNumActive) {
                 synchronized(this) {
                     pool.decrementActiveCount();
                     allocate();
                 }
             }
         }
     }
 
     /**
      * <p>Invalidates the object instance associated with the given key.  Decrements the active count
      * associated with the given keyed pool and destroys the instance.</p>
      * 
      * @param key pool key
      * @param obj instance to invalidate
      * @throws Exception if an exception occurs destroying the object
      */
     public void invalidateObject(Object key, Object obj) throws Exception {
         try {
             _factory.destroyObject(key, obj);
         } finally {
             synchronized (this) {
                 ObjectQueue pool = (ObjectQueue) (_poolMap.get(key));
                 if (null == pool) {
                     pool = new ObjectQueue();
                     _poolMap.put(key, pool);
                     _poolList.add(key);
                 }
                 pool.decrementActiveCount();
                 allocate(); // _totalActive has changed
             }
         }
     }
 
     /**
      * Create an object using the {@link KeyedPoolableObjectFactory#makeObject factory},
      * passivate it, and then place it in the idle object pool.
      * <code>addObject</code> is useful for "pre-loading" a pool with idle objects.
      *
      * @param key the key a new instance should be added to
      * @throws Exception when {@link KeyedPoolableObjectFactory#makeObject} fails.
      * @throws IllegalStateException when no {@link #setFactory factory} has been set or after {@link #close} has been
      * called on this pool.
      */
     public void addObject(Object key) throws Exception {
         assertOpen();
         if (_factory == null) {
             throw new IllegalStateException("Cannot add objects without a factory.");
         }
         Object obj = _factory.makeObject(key);
         try {
             assertOpen();
             addObjectToPool(key, obj, false);
         } catch (IllegalStateException ex) { // Pool closed
             try {
                 _factory.destroyObject(key, obj);
             } catch (Exception ex2) {
                 // swallow
             }
             throw ex;
         }
     }
 
     /**
      * Registers a key for pool control.
      *
      * If <code>populateImmediately</code> is <code>true</code> and
      * <code>minIdle > 0,</code> the pool under the given key will be
      * populated immediately with <code>minIdle</code> idle instances.
      *
      * @param key - The key to register for pool control.
      * @param populateImmediately - If this is <code>true</code>, the pool
      * will be populated immediately.
      * @since Pool 1.3
      */
     public synchronized void preparePool(Object key, boolean populateImmediately) {
         ObjectQueue pool = (ObjectQueue)(_poolMap.get(key));
         if (null == pool) {
             pool = new ObjectQueue();
             _poolMap.put(key,pool);
             _poolList.add(key);
         }
 
         if (populateImmediately) {
             try {
                 // Create the pooled objects
                 ensureMinIdle(key);
             }
             catch (Exception e) {
                 //Do nothing
             }
         }
     }
 
     /**
      * Closes the keyed object pool.  Once the pool is closed, {@link #borrowObject(Object)}
      * will fail with IllegalStateException, but {@link #returnObject(Object, Object)} and
      * {@link #invalidateObject(Object, Object)} will continue to work. This method does not
      * {@link #clear()} the pool. The method is idempotent - that is, it is OK to call it on a closed
      * pool. 
      * 
      * @throws Exception
      */
     public void close() throws Exception {
         super.close();
         synchronized (this) {
             clear();
             if (null != _evictionCursor) {
                 _evictionCursor.close();
                 _evictionCursor = null;
             }
             if (null != _evictionKeyCursor) {
                 _evictionKeyCursor.close();
                 _evictionKeyCursor = null;
             }
             startEvictor(-1L);
         }
     }
 
     /**
      * <p>Sets the keyed poolable object factory associated with this pool.</p>
      * 
      * <p>If this method is called when objects are checked out of any of the keyed pools,
      * an IllegalStateException is thrown.  Calling this method also has the side effect of
      * destroying any idle instances in existing keyed pools.</p>
      * 
      * @param factory KeyedPoolableObjectFactory to use when creating keyed object pool instances
      * @throws IllegalStateException if there are active (checked out) instances associated with this keyed object pool
      */
     public void setFactory(KeyedPoolableObjectFactory factory) throws IllegalStateException {
         Map toDestroy = new HashMap();
         synchronized (this) {
             assertOpen();
             if (0 < getNumActive()) {
                 throw new IllegalStateException("Objects are already active");
             } else {
                 for (Iterator it = _poolMap.keySet().iterator(); it.hasNext();) {
                     Object key = it.next();
                     ObjectQueue pool = (ObjectQueue)_poolMap.get(key);
                     if (pool != null) {
                         // Copy objects to new list so pool.queue can be cleared
                         // inside the sync
                         List objects = new ArrayList();
                         objects.addAll(pool.queue);
                         toDestroy.put(key, objects);
                         it.remove();
                         _poolList.remove(key);
                         _totalIdle = _totalIdle - pool.queue.size();
                         _totalInternalProcessing =
                             _totalInternalProcessing + pool.queue.size();
                         pool.queue.clear();
                     }
                 }
                 _factory = factory;
             }
         }
         destroy(toDestroy);
     }
 
     /**
      * <p>Perform <code>numTests</code> idle object eviction tests, evicting
      * examined objects that meet the criteria for eviction. If
      * <code>testWhileIdle</code> is true, examined objects are validated
      * when visited (and removed if invalid); otherwise only objects that
      * have been idle for more than <code>minEvicableIdletimeMillis</code>
      * are removed.</p>
      *
      * <p>Successive activations of this method examine objects in keyed pools
      * in sequence, cycling through the keys and examining objects in
      * oldest-to-youngest order within the keyed pools.</p>
      *
      * @throws Exception when there is a problem evicting idle objects.
      */
     public void evict() throws Exception {
         Object key = null;
         boolean testWhileIdle;
         long minEvictableIdleTimeMillis;
 
         synchronized (this) {
             // Get local copy of current config. Can't sync when used later as
             // it can result in a deadlock. Has the added advantage that config
             // is consistent for entire method execution
             testWhileIdle = _testWhileIdle;
             minEvictableIdleTimeMillis = _minEvictableIdleTimeMillis;
 
             // Initialize key to last key value
             if (_evictionKeyCursor != null &&
                     _evictionKeyCursor._lastReturned != null) {
                 key = _evictionKeyCursor._lastReturned.value();
             }
         }
 
         for (int i=0, m=getNumTests(); i<m; i++) {
             final ObjectTimestampPair pair;
             synchronized (this) {
                 // make sure pool map is not empty; otherwise do nothing
                 if (_poolMap == null || _poolMap.size() == 0) {
                     continue;
                 }
 
                 // if we don't have a key cursor, then create one
                 if (null == _evictionKeyCursor) {
                     resetEvictionKeyCursor();
                     key = null;
                 }
 
                 // if we don't have an object cursor, create one
                 if (null == _evictionCursor) {
                     // if the _evictionKeyCursor has a next value, use this key
                     if (_evictionKeyCursor.hasNext()) {
                         key = _evictionKeyCursor.next();
                         resetEvictionObjectCursor(key);
                     } else {
                         // Reset the key cursor and try again
                         resetEvictionKeyCursor();
                         if (_evictionKeyCursor != null) {
                             if (_evictionKeyCursor.hasNext()) {
                                 key = _evictionKeyCursor.next();
                                 resetEvictionObjectCursor(key);
                             }
                         }
                     }
                 }
 
                 if (_evictionCursor == null) {
                     continue; // should never happen; do nothing
                 }
 
                 // If eviction cursor is exhausted, try to move
                 // to the next key and reset
                 if ((_lifo && !_evictionCursor.hasPrevious()) ||
                         (!_lifo && !_evictionCursor.hasNext())) {
                     if (_evictionKeyCursor != null) {
                         if (_evictionKeyCursor.hasNext()) {
                             key = _evictionKeyCursor.next();
                             resetEvictionObjectCursor(key);
                         } else { // Need to reset Key cursor
                             resetEvictionKeyCursor();
                             if (_evictionKeyCursor != null) {
                                 if (_evictionKeyCursor.hasNext()) {
                                     key = _evictionKeyCursor.next();
                                     resetEvictionObjectCursor(key);
                                 }
                             }
                         }
                     }
                 }
 
                 if ((_lifo && !_evictionCursor.hasPrevious()) ||
                         (!_lifo && !_evictionCursor.hasNext())) {
                     continue; // reset failed, do nothing
                 }
 
                 // if LIFO and the _evictionCursor has a previous object,
                 // or FIFO and _evictionCursor has a next object, test it
                 pair = _lifo ?
                         (ObjectTimestampPair) _evictionCursor.previous() :
                         (ObjectTimestampPair) _evictionCursor.next();
                 _evictionCursor.remove();
                 _totalIdle--;
                 _totalInternalProcessing++;
             }
 
             boolean removeObject=false;
             if ((minEvictableIdleTimeMillis > 0) &&
                (System.currentTimeMillis() - pair.tstamp >
                minEvictableIdleTimeMillis)) {
                 removeObject=true;
             }
             if (testWhileIdle && removeObject == false) {
                 boolean active = false;
                 try {
                     _factory.activateObject(key,pair.value);
                     active = true;
                 } catch(Exception e) {
                     removeObject=true;
                 }
                 if (active) {
                     if (!_factory.validateObject(key,pair.value)) {
                         removeObject=true;
                     } else {
                         try {
                             _factory.passivateObject(key,pair.value);
                         } catch(Exception e) {
                             removeObject=true;
                         }
                     }
                 }
             }
 
             if (removeObject) {
                 try {
                     _factory.destroyObject(key, pair.value);
                 } catch(Exception e) {
                     // ignored
                 } finally {
                     // Do not remove the key from the _poolList or _poolmap,
                     // even if the list stored in the _poolMap for this key is
                     // empty when minIdle > 0.
                     //
                     // Otherwise if it was the last object for that key,
                     // drop that pool
                     if (_minIdle == 0) {
                         synchronized (this) {
                             ObjectQueue objectQueue =
                                 (ObjectQueue)_poolMap.get(key);
                             if (objectQueue != null &&
                                     objectQueue.queue.isEmpty()) {
                                 _poolMap.remove(key);
                                 _poolList.remove(key);
                             }
                         }
                     }
                 }
             }
             synchronized (this) {
                 if (!removeObject) {
                     _evictionCursor.add(pair);
                     _totalIdle++;
                     if (_lifo) {
                         // Skip over the element we just added back
                         _evictionCursor.previous();
                     }
                 }
                 _totalInternalProcessing--;
             }
         }
     }
 
     /**
      * Resets the eviction key cursor and closes any
      * associated eviction object cursor
      */
     private void resetEvictionKeyCursor() {
         if (_evictionKeyCursor != null) {
             _evictionKeyCursor.close();
         }
         _evictionKeyCursor = _poolList.cursor();
         if (null != _evictionCursor) {
             _evictionCursor.close();
             _evictionCursor = null;
         }
     }
 
     /**
      * Resets the eviction object cursor for the given key
      *
      * @param key eviction key
      */
     private void resetEvictionObjectCursor(Object key) {
         if (_evictionCursor != null) {
             _evictionCursor.close();
         }
         if (_poolMap == null) {
             return;
         }
         ObjectQueue pool = (ObjectQueue) (_poolMap.get(key));
         if (pool != null) {
             CursorableLinkedList queue = pool.queue;
             _evictionCursor = queue.cursor(_lifo ? queue.size() : 0);
         }
     }
 
     /**
      * Iterates through all the known keys and creates any necessary objects to maintain
      * the minimum level of pooled objects.
      * @see #getMinIdle
      * @see #setMinIdle
      * @throws Exception If there was an error whilst creating the pooled objects.
      */
     private void ensureMinIdle() throws Exception {
         //Check if should sustain the pool
         if (_minIdle > 0) {
             Object[] keysCopy;
             synchronized(this) {
                 // Get the current set of keys
                 keysCopy = _poolMap.keySet().toArray();
             }
 
             // Loop through all elements in _poolList
             // Find out the total number of max active and max idle for that class
             // If the number is less than the minIdle, do creation loop to boost numbers
             for (int i=0; i < keysCopy.length; i++) {
                 //Get the next key to process
                 ensureMinIdle(keysCopy[i]);
             }
         }
     }
 
     /**
      * Re-creates any needed objects to maintain the minimum levels of
      * pooled objects for the specified key.
      *
      * This method uses {@link #calculateDeficit} to calculate the number
      * of objects to be created. {@link #calculateDeficit} can be overridden to
      * provide a different method of calculating the number of objects to be
      * created.
      * @param key The key to process
      * @throws Exception If there was an error whilst creating the pooled objects
      */
     private void ensureMinIdle(Object key) throws Exception {
         // Calculate current pool objects
         ObjectQueue pool;
         synchronized(this) {
             pool = (ObjectQueue)(_poolMap.get(key));
         }
         if (pool == null) {
             return;
         }
 
         // 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(pool, false);
 
         for (int i = 0; i < objectDeficit && calculateDeficit(pool, true) > 0; i++) {
             try {
                 addObject(key);
             } finally {
                 synchronized (this) {
                     pool.decrementInternalProcessingCount();
                     allocate();
                 }
             }
         }
     }
 
     //--- non-public methods ----------------------------------------
 
     /**
      * Start the eviction thread or service, or when
      * <code>delay</code> is non-positive, stop it
      * if it is already running.
      *
      * @param delay milliseconds between evictor runs.
      */
     protected synchronized void startEvictor(long delay) {
         if (null != _evictor) {
             EvictionTimer.cancel(_evictor);
             _evictor = null;
         }
         if (delay > 0) {
             _evictor = new Evictor();
             EvictionTimer.schedule(_evictor, delay, delay);
         }
     }
 
     /**
      * Returns pool info including {@link #getNumActive()}, {@link #getNumIdle()}
      * and currently defined keys.
      * 
      * @return string containing debug information
      */
     synchronized String debugInfo() {
         StringBuffer buf = new StringBuffer();
         buf.append("Active: ").append(getNumActive()).append("\n");
         buf.append("Idle: ").append(getNumIdle()).append("\n");
         Iterator it = _poolMap.keySet().iterator();
         while (it.hasNext()) {
             Object key = it.next();
             buf.append("\t").append(key).append(" ").append(_poolMap.get(key)).append("\n");
         }
         return buf.toString();
     }
 
     /** 
      * Returns the number of tests to be performed in an Evictor run,
      * based on the current values of <code>_numTestsPerEvictionRun</code>
      * and <code>_totalIdle</code>.
      * 
      * @see #setNumTestsPerEvictionRun
      * @return the number of tests for the Evictor to run
      */
     private synchronized int getNumTests() {
         if (_numTestsPerEvictionRun >= 0) {
             return Math.min(_numTestsPerEvictionRun, _totalIdle);
         } else {
             return(int)(Math.ceil(_totalIdle/Math.abs((double)_numTestsPerEvictionRun)));
         }
     }
 
     /**
      * This returns the number of objects to create during the pool
      * sustain cycle. This will ensure that the minimum number of idle
      * instances is maintained without going past the maxActive value.
      * 
      * @param pool the ObjectPool to calculate the deficit for
      * @param incrementInternal - Should the count of objects currently under
      *                            some form of internal processing be
      *                            incremented?
      * @return The number of objects to be created
      */
     private synchronized int calculateDeficit(ObjectQueue pool,
             boolean incrementInternal) {
         int objectDefecit = 0;
 
         //Calculate no of objects needed to be created, in order to have
         //the number of pooled objects < maxActive();
         objectDefecit = getMinIdle() - pool.queue.size();
         if (getMaxActive() > 0) {
             int growLimit = Math.max(0, getMaxActive() - pool.activeCount - pool.queue.size() - pool.internalProcessingCount);
             objectDefecit = Math.min(objectDefecit, growLimit);
         }
 
         // Take the maxTotal limit into account
         if (getMaxTotal() > 0) {
             int growLimit = Math.max(0, getMaxTotal() - getNumActive() - getNumIdle() - _totalInternalProcessing);
             objectDefecit = Math.min(objectDefecit, growLimit);
         }
 
         if (incrementInternal && objectDefecit > 0) {
             pool.incrementInternalProcessingCount();
         }
         return objectDefecit;
     }
 
     //--- inner classes ----------------------------------------------
 
     /**
      * A "struct" that keeps additional information about the actual queue of pooled objects.
      */
     private class ObjectQueue {
         /** Number of instances checked out to clients from this queue */
         private int activeCount = 0;
         
         /** Idle instance queue */
         private final CursorableLinkedList queue = new CursorableLinkedList();
         
         /** Number of instances in process of being created */
         private int internalProcessingCount = 0;
 
         /** Increment the active count for this queue */
         void incrementActiveCount() {
             synchronized (GenericKeyedObjectPool.this) {
                 _totalActive++;
             }
             activeCount++;
         }
 
         /** Decrement the active count for this queue */
         void decrementActiveCount() {
             synchronized (GenericKeyedObjectPool.this) {
                 _totalActive--;
             }
             if (activeCount > 0) {
                 activeCount--;
             }
         }
 
         /** Record the fact that one more instance is queued for creation */
         void incrementInternalProcessingCount() {
             synchronized (GenericKeyedObjectPool.this) {
                 _totalInternalProcessing++;
             }
             internalProcessingCount++;
         }
 
         /** Decrement the number of instances in process of being created */
         void decrementInternalProcessingCount() {
             synchronized (GenericKeyedObjectPool.this) {
                 _totalInternalProcessing--;
             }
             internalProcessingCount--;
         }
     }
 
     /**
      * A simple "struct" encapsulating an object instance and a timestamp.
      *
      * Implements Comparable, objects are sorted from old to new.
      *
      * This is also used by {@link GenericObjectPool}.
      */
     static class ObjectTimestampPair implements Comparable {
         
         /** Object instance */
         Object value;
         
         /** timestamp */
         long tstamp;
 
         /**
          * Create a new ObjectTimestampPair using the given object and the current system time.
          * @param val object instance
          */
         ObjectTimestampPair(Object val) {
             this(val, System.currentTimeMillis());
         }
 
         /**
          * Create a new ObjectTimeStampPair using the given object and timestamp value.
          * @param val object instance
          * @param time long representation of timestamp
          */
         ObjectTimestampPair(Object val, long time) {
             value = val;
             tstamp = time;
         }
 
         /**
          * Returns a string representation.
          * 
          * @return String representing this ObjectTimestampPair
          */
         public String toString() {
             return value + ";" + tstamp;
         }
 
         /**
          * Compares this to another object by casting the argument to an
          * ObjectTimestampPair.
          * 
          * @param obj object to cmpare
          * @return result of comparison
          */
         public int compareTo(Object obj) {
             return compareTo((ObjectTimestampPair) obj);
         }
 
         /**
          * Compares this to another ObjectTimestampPair, using the timestamp as basis for comparison.
          * Implementation is consistent with equals.
          * 
          * @param other object to compare
          * @return result of comparison
          */
         public int compareTo(ObjectTimestampPair other) {
             final long tstampdiff = this.tstamp - other.tstamp;
             if (tstampdiff == 0) {
                 // make sure the natural ordering is consistent with equals
                 // see java.lang.Comparable Javadocs
                 return System.identityHashCode(this) - System.identityHashCode(other);
             } else {
                 // handle int overflow
                 return (int)Math.min(Math.max(tstampdiff, Integer.MIN_VALUE), Integer.MAX_VALUE);
             }
         }
     }
 
     /**
      * The idle object evictor {@link TimerTask}.
      * @see GenericKeyedObjectPool#setTimeBetweenEvictionRunsMillis
      */
     private class Evictor extends TimerTask {
         /**
          * Run pool maintenance.  Evict objects qualifying for eviction and then
          * invoke {@link GenericKeyedObjectPool#ensureMinIdle()}.
          */
         public void run() {
             //Evict from the pool
             try {
                 evict();
             } catch(Exception e) {
                 // ignored
             } catch(OutOfMemoryError oome) {
                 // Log problem but give evictor thread a chance to continue in
                 // case error is recoverable
                 oome.printStackTrace(System.err);
             }
             //Re-create idle instances.
             try {
                 ensureMinIdle();
             } catch (Exception e) {
                 // ignored
             }
         }
     }
 
     /**
      * A simple "struct" encapsulating the
      * configuration information for a <code>GenericKeyedObjectPool</code>.
      * @see GenericKeyedObjectPool#GenericKeyedObjectPool(KeyedPoolableObjectFactory,GenericKeyedObjectPool.Config)
      * @see GenericKeyedObjectPool#setConfig
      */
     public static class Config {
         /**
          * @see GenericKeyedObjectPool#setMaxIdle
          */
         public int maxIdle = GenericKeyedObjectPool.DEFAULT_MAX_IDLE;
         /**
          * @see GenericKeyedObjectPool#setMaxActive
          */
         public int maxActive = GenericKeyedObjectPool.DEFAULT_MAX_ACTIVE;
         /**
          * @see GenericKeyedObjectPool#setMaxTotal
          */
         public int maxTotal = GenericKeyedObjectPool.DEFAULT_MAX_TOTAL;
         /**
          * @see GenericKeyedObjectPool#setMinIdle
          */
         public int minIdle = GenericKeyedObjectPool.DEFAULT_MIN_IDLE;
         /**
          * @see GenericKeyedObjectPool#setMaxWait
          */
         public long maxWait = GenericKeyedObjectPool.DEFAULT_MAX_WAIT;
         /**
          * @see GenericKeyedObjectPool#setWhenExhaustedAction
          */
         public byte whenExhaustedAction = GenericKeyedObjectPool.DEFAULT_WHEN_EXHAUSTED_ACTION;
         /**
          * @see GenericKeyedObjectPool#setTestOnBorrow
          */
         public boolean testOnBorrow = GenericKeyedObjectPool.DEFAULT_TEST_ON_BORROW;
         /**
          * @see GenericKeyedObjectPool#setTestOnReturn
          */
         public boolean testOnReturn = GenericKeyedObjectPool.DEFAULT_TEST_ON_RETURN;
         /**
          * @see GenericKeyedObjectPool#setTestWhileIdle
          */
         public boolean testWhileIdle = GenericKeyedObjectPool.DEFAULT_TEST_WHILE_IDLE;
         /**
          * @see GenericKeyedObjectPool#setTimeBetweenEvictionRunsMillis
          */
         public long timeBetweenEvictionRunsMillis = GenericKeyedObjectPool.DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;
         /**
          * @see GenericKeyedObjectPool#setNumTestsPerEvictionRun
          */
         public int numTestsPerEvictionRun =  GenericKeyedObjectPool.DEFAULT_NUM_TESTS_PER_EVICTION_RUN;
         /**
          * @see GenericKeyedObjectPool#setMinEvictableIdleTimeMillis
          */
         public long minEvictableIdleTimeMillis = GenericKeyedObjectPool.DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;
         /**
          * @see GenericKeyedObjectPool#setLifo
          */
         public boolean lifo = GenericKeyedObjectPool.DEFAULT_LIFO;
     }
 
     /**
      * Latch used to control allocation order of objects to threads to ensure
      * fairness. That is, for each key, objects are allocated to threads in the order
      * that threads request objects.
      * 
      * @since 1.5
      */
     private static final class Latch {
         
         /** key of associated pool */
         private final Object _key;
         
         /** keyed pool associated with this latch */
         private ObjectQueue _pool;
         
         /** holds an ObjectTimestampPair when this latch has been allocated an instance */
         private ObjectTimestampPair _pair;
         
         /** indicates that this latch can create an instance */
         private boolean _mayCreate = false;
 
         /**
          * Create a latch with the given key
          * @param key key of the pool associated with this latch
          */
         private Latch(Object key) {
             _key = key;
         }
 
         /**
          * Retuns the key of the associated pool
          * @return associated pool key
          */
         private synchronized Object getkey() {
             return _key;
         }
 
         /**
          * Returns the pool associated with this latch
          * @return pool
          */
         private synchronized ObjectQueue getPool() {
             return _pool;
         }
         
         /**
          * Sets the pool associated with this latch
          * @param pool the pool
          */
         private synchronized void setPool(ObjectQueue pool) {
             _pool = pool;
         }
 
         /**
          * Gets the ObjectTimestampPair allocated to this latch.
          * Returns null if this latch does not have an instance allocated to it. 
          * @return the associated ObjectTimestampPair
          */
         private synchronized ObjectTimestampPair getPair() {
             return _pair;
         }
         
         /**
          * Allocate an ObjectTimestampPair to this latch.
          * @param pair ObjectTimestampPair on this latch
          */
         private synchronized void setPair(ObjectTimestampPair pair) {
             _pair = pair;
         }
 
         /**
          * Whether or not this latch can create an instance
          * @return true if this latch has an instance creation permit
          */
         private synchronized boolean mayCreate() {
             return _mayCreate;
         }
         
         /**
          * Sets the mayCreate property
          * 
          * @param mayCreate true means this latch can create an instance
          */
         private synchronized void setMayCreate(boolean mayCreate) {
             _mayCreate = mayCreate;
         }
 
         /**
          * Reset the latch data. Used when an allocation fails and the latch
          * needs to be re-added to the queue.
          */
         private synchronized void reset() {
             _pair = null;
             _mayCreate = false;
         }
     }
 
     //--- protected attributes ---------------------------------------
 
     /**
      * The cap on the number of idle instances in the pool.
      * @see #setMaxIdle
      * @see #getMaxIdle
      */
     private int _maxIdle = DEFAULT_MAX_IDLE;
 
     /**
      * The minimum no of idle objects to keep in the pool.
      * @see #setMinIdle
      * @see #getMinIdle
      */
     private int _minIdle = DEFAULT_MIN_IDLE;
 
     /**
      * The cap on the number of active instances from the pool.
      * @see #setMaxActive
      * @see #getMaxActive
      */
     private int _maxActive = DEFAULT_MAX_ACTIVE;
 
     /**
      * The cap on the total number of instances from the pool if non-positive.
      * @see #setMaxTotal
      * @see #getMaxTotal
      */
     private int _maxTotal = DEFAULT_MAX_TOTAL;
 
     /**
      * 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 or equal to 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 <code>true</code>, objects will be
      * {@link org.apache.commons.pool.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 volatile boolean _testOnBorrow = DEFAULT_TEST_ON_BORROW;
 
     /**
      * When <code>true</code>, objects will be
      * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
      * before being returned to the pool within the
      * {@link #returnObject}.
      *
      * @see #getTestOnReturn
      * @see #setTestOnReturn
      */
     private volatile boolean _testOnReturn = DEFAULT_TEST_ON_RETURN;
 
     /**
      * When <code>true</code>, objects will be
      * {@link org.apache.commons.pool.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 number of objects to examine during each run of the
      * idle object evictor thread (if any).
      * <p>
      * When a negative value is supplied, <code>ceil({@link #getNumIdle})/abs({@link #getNumTestsPerEvictionRun})</code>
      * tests will be run.  I.e., when the value is <code>-n</code>, roughly one <code>n</code>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 eligible 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;
 
     /** My hash of pools (ObjectQueue). */
     private Map _poolMap = null;
 
     /** The total number of active instances. */
     private int _totalActive = 0;
 
     /** The total number of idle instances. */
     private int _totalIdle = 0;
 
     /**
      * The number of objects subject to some form of internal processing
      * (usually creation or destruction) that should be included in the total
      * number of objects but are neither active nor idle.
      */
     private int _totalInternalProcessing = 0;
 
     /** My {@link KeyedPoolableObjectFactory}. */
     private KeyedPoolableObjectFactory _factory = null;
 
     /**
      * My idle object eviction {@link TimerTask}, if any.
      */
     private Evictor _evictor = null;
 
     /**
      * A cursorable list of my pools.
      * @see GenericKeyedObjectPool.Evictor#run
      */
     private CursorableLinkedList _poolList = null;
 
     /** Eviction cursor (over instances within-key) */
     private CursorableLinkedList.Cursor _evictionCursor = null;
     
     /** Eviction cursor (over keys) */
     private CursorableLinkedList.Cursor _evictionKeyCursor = null;
 
     /** Whether or not the pools behave as LIFO queues (last in first out) */
     private boolean _lifo = DEFAULT_LIFO;
 
     /**
      * Used to track the order in which threads call {@link #borrowObject()} so
      * that objects can be allocated in the order in which the threads requested
      * them.
      */
     private LinkedList _allocationQueue = new LinkedList();
 
 }