001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    
018    package org.apache.commons.pool.impl;
019    
020    import java.util.ArrayList;
021    import java.util.Collection;
022    import java.util.HashMap;
023    import java.util.Iterator;
024    import java.util.LinkedList;
025    import java.util.List;
026    import java.util.Map;
027    import java.util.NoSuchElementException;
028    import java.util.Set;
029    import java.util.TreeMap;
030    import java.util.TimerTask;
031    
032    import org.apache.commons.pool.BaseKeyedObjectPool;
033    import org.apache.commons.pool.KeyedObjectPool;
034    import org.apache.commons.pool.KeyedPoolableObjectFactory;
035    
036    /**
037     * A configurable <code>KeyedObjectPool</code> implementation.
038     * <p>
039     * When coupled with the appropriate {@link KeyedPoolableObjectFactory},
040     * <code>GenericKeyedObjectPool</code> provides robust pooling functionality for
041     * keyed objects. A <code>GenericKeyedObjectPool</code> can be viewed as a map
042     * of pools, keyed on the (unique) key values provided to the
043     * {@link #preparePool preparePool}, {@link #addObject addObject} or
044     * {@link #borrowObject borrowObject} methods. Each time a new key value is
045     * provided to one of these methods, a new pool is created under the given key
046     * to be managed by the containing <code>GenericKeyedObjectPool.</code>
047     * </p>
048     * <p>A <code>GenericKeyedObjectPool</code> provides a number of configurable
049     * parameters:</p>
050     * <ul>
051     *  <li>
052     *    {@link #setMaxActive maxActive} controls the maximum number of objects
053     *    (per key) that can allocated by the pool (checked out to client threads,
054     *    or idle in the pool) at one time.  When non-positive, there is no limit
055     *    to the number of objects per key. When {@link #setMaxActive maxActive} is
056     *    reached, the keyed pool is said to be exhausted.  The default setting for
057     *    this parameter is 8.
058     *  </li>
059     *  <li>
060     *    {@link #setMaxTotal maxTotal} sets a global limit on the number of objects
061     *    that can be in circulation (active or idle) within the combined set of
062     *    pools.  When non-positive, there is no limit to the total number of
063     *    objects in circulation. When {@link #setMaxTotal maxTotal} is exceeded,
064     *    all keyed pools are exhausted. When <code>maxTotal</code> is set to a
065     *    positive value and {@link #borrowObject borrowObject} is invoked
066     *    when at the limit with no idle instances available, an attempt is made to
067     *    create room by clearing the oldest 15% of the elements from the keyed
068     *    pools. The default setting for this parameter is -1 (no limit).
069     *  </li>
070     *  <li>
071     *    {@link #setMaxIdle maxIdle} controls the maximum number of objects that can
072     *    sit idle in the pool (per key) at any time.  When negative, there
073     *    is no limit to the number of objects that may be idle per key. The
074     *    default setting for this parameter is 8.
075     *  </li>
076     *  <li>
077     *    {@link #setWhenExhaustedAction whenExhaustedAction} specifies the
078     *    behavior of the {@link #borrowObject borrowObject} method when a keyed
079     *    pool is exhausted:
080     *    <ul>
081     *    <li>
082     *      When {@link #setWhenExhaustedAction whenExhaustedAction} is
083     *      {@link #WHEN_EXHAUSTED_FAIL}, {@link #borrowObject borrowObject} will throw
084     *      a {@link NoSuchElementException}
085     *    </li>
086     *    <li>
087     *      When {@link #setWhenExhaustedAction whenExhaustedAction} is
088     *      {@link #WHEN_EXHAUSTED_GROW}, {@link #borrowObject borrowObject} will create a new
089     *      object and return it (essentially making {@link #setMaxActive maxActive}
090     *      meaningless.)
091     *    </li>
092     *    <li>
093     *      When {@link #setWhenExhaustedAction whenExhaustedAction}
094     *      is {@link #WHEN_EXHAUSTED_BLOCK}, {@link #borrowObject borrowObject} will block
095     *      (invoke {@link Object#wait() wait} until a new or idle object is available.
096     *      If a positive {@link #setMaxWait maxWait}
097     *      value is supplied, the {@link #borrowObject borrowObject} will block for at
098     *      most that many milliseconds, after which a {@link NoSuchElementException}
099     *      will be thrown.  If {@link #setMaxWait maxWait} is non-positive,
100     *      the {@link #borrowObject borrowObject} method will block indefinitely.
101     *    </li>
102     *    </ul>
103     *    The default <code>whenExhaustedAction</code> setting is
104     *    {@link #WHEN_EXHAUSTED_BLOCK}.
105     *  </li>
106     *  <li>
107     *    When {@link #setTestOnBorrow testOnBorrow} is set, the pool will
108     *    attempt to validate each object before it is returned from the
109     *    {@link #borrowObject borrowObject} method. (Using the provided factory's
110     *    {@link KeyedPoolableObjectFactory#validateObject validateObject} method.)
111     *    Objects that fail to validate will be dropped from the pool, and a
112     *    different object will be borrowed. The default setting for this parameter
113     *    is <code>false.</code>
114     *  </li>
115     *  <li>
116     *    When {@link #setTestOnReturn testOnReturn} is set, the pool will
117     *    attempt to validate each object before it is returned to the pool in the
118     *    {@link #returnObject returnObject} method. (Using the provided factory's
119     *    {@link KeyedPoolableObjectFactory#validateObject validateObject}
120     *    method.)  Objects that fail to validate will be dropped from the pool.
121     *    The default setting for this parameter is <code>false.</code>
122     *  </li>
123     * </ul>
124     * <p>
125     * Optionally, one may configure the pool to examine and possibly evict objects
126     * as they sit idle in the pool and to ensure that a minimum number of idle
127     * objects is maintained for each key. This is performed by an
128     * "idle object eviction" thread, which runs asynchronously. Caution should be
129     * used when configuring this optional feature. Eviction runs require an
130     * exclusive synchronization lock on the pool, so if they run too frequently
131     * and / or incur excessive latency when creating, destroying or validating
132     * object instances, performance issues may result.  The idle object eviction
133     * thread may be configured using the following attributes:
134     * <ul>
135     *  <li>
136     *   {@link #setTimeBetweenEvictionRunsMillis timeBetweenEvictionRunsMillis}
137     *   indicates how long the eviction thread should sleep before "runs" of examining
138     *   idle objects.  When non-positive, no eviction thread will be launched. The
139     *   default setting for this parameter is -1 (i.e., by default, idle object
140     *   eviction is disabled).
141     *  </li>
142     *  <li>
143     *   {@link #setMinEvictableIdleTimeMillis minEvictableIdleTimeMillis}
144     *   specifies the minimum amount of time that an object may sit idle in the
145     *   pool before it is eligible for eviction due to idle time.  When
146     *   non-positive, no object will be dropped from the pool due to idle time
147     *   alone.  This setting has no effect unless
148     *   <code>timeBetweenEvictionRunsMillis > 0.</code>  The default setting
149     *   for this parameter is 30 minutes.
150     *  </li>
151     *  <li>
152     *   {@link #setTestWhileIdle testWhileIdle} indicates whether or not idle
153     *   objects should be validated using the factory's
154     *   {@link KeyedPoolableObjectFactory#validateObject validateObject} method
155     *   during idle object eviction runs.  Objects that fail to validate will be
156     *   dropped from the pool. This setting has no effect unless
157     *   <code>timeBetweenEvictionRunsMillis > 0.</code>  The default setting
158     *   for this parameter is <code>false.</code>
159     *  </li>
160     *  <li>
161     *    {@link #setMinIdle minIdle} sets a target value for the minimum number of
162     *    idle objects (per key) that should always be available. If this parameter
163     *    is set to a positive number and
164     *    <code>timeBetweenEvictionRunsMillis > 0,</code> each time the idle object
165     *    eviction thread runs, it will try to create enough idle instances so that
166     *    there will be <code>minIdle</code> idle instances available under each
167     *    key. This parameter is also used by {@link #preparePool preparePool}
168     *    if <code>true</code> is provided as that method's
169     *    <code>populateImmediately</code> parameter. The default setting for this
170     *    parameter is 0.
171     *  </li>
172     * </ul>
173     * <p>
174     * The pools can be configured to behave as LIFO queues with respect to idle
175     * objects - always returning the most recently used object from the pool,
176     * or as FIFO queues, where borrowObject always returns the oldest object
177     * in the idle object pool.
178     * <ul>
179     *  <li>
180     *   {@link #setLifo <i>Lifo</i>}
181     *   determines whether or not the pools return idle objects in
182     *   last-in-first-out order. The default setting for this parameter is
183     *   <code>true.</code>
184     *  </li>
185     * </ul>
186     * <p>
187     * GenericKeyedObjectPool is not usable without a {@link KeyedPoolableObjectFactory}.  A
188     * non-<code>null</code> factory must be provided either as a constructor argument
189     * or via a call to {@link #setFactory setFactory} before the pool is used.
190     * </p>
191     * <p>
192     * Implementation note: To prevent possible deadlocks, care has been taken to
193     * ensure that no call to a factory method will occur within a synchronization
194     * block. See POOL-125 and DBCP-44 for more information.
195     * </p>
196     * @see GenericObjectPool
197     * @author Rodney Waldhoff
198     * @author Dirk Verbeeck
199     * @author Sandy McArthur
200     * @version $Revision: 791907 $ $Date: 2009-07-07 12:56:33 -0400 (Tue, 07 Jul 2009) $
201     * @since Pool 1.0
202     */
203    public class GenericKeyedObjectPool extends BaseKeyedObjectPool implements KeyedObjectPool {
204    
205        //--- public constants -------------------------------------------
206    
207        /**
208         * A "when exhausted action" type indicating that when the pool is
209         * exhausted (i.e., the maximum number of active objects has
210         * been reached), the {@link #borrowObject}
211         * method should fail, throwing a {@link NoSuchElementException}.
212         * @see #WHEN_EXHAUSTED_BLOCK
213         * @see #WHEN_EXHAUSTED_GROW
214         * @see #setWhenExhaustedAction
215         */
216        public static final byte WHEN_EXHAUSTED_FAIL   = 0;
217    
218        /**
219         * A "when exhausted action" type indicating that when the pool
220         * is exhausted (i.e., the maximum number
221         * of active objects has been reached), the {@link #borrowObject}
222         * method should block until a new object is available, or the
223         * {@link #getMaxWait maximum wait time} has been reached.
224         * @see #WHEN_EXHAUSTED_FAIL
225         * @see #WHEN_EXHAUSTED_GROW
226         * @see #setMaxWait
227         * @see #getMaxWait
228         * @see #setWhenExhaustedAction
229         */
230        public static final byte WHEN_EXHAUSTED_BLOCK  = 1;
231    
232        /**
233         * A "when exhausted action" type indicating that when the pool is
234         * exhausted (i.e., the maximum number
235         * of active objects has been reached), the {@link #borrowObject}
236         * method should simply create a new object anyway.
237         * @see #WHEN_EXHAUSTED_FAIL
238         * @see #WHEN_EXHAUSTED_GROW
239         * @see #setWhenExhaustedAction
240         */
241        public static final byte WHEN_EXHAUSTED_GROW   = 2;
242    
243        /**
244         * The default cap on the number of idle instances (per key) in the pool.
245         * @see #getMaxIdle
246         * @see #setMaxIdle
247         */
248        public static final int DEFAULT_MAX_IDLE  = 8;
249    
250        /**
251         * The default cap on the total number of active instances (per key)
252         * from the pool.
253         * @see #getMaxActive
254         * @see #setMaxActive
255         */
256        public static final int DEFAULT_MAX_ACTIVE  = 8;
257    
258        /**
259         * The default cap on the the overall maximum number of objects that can
260         * exist at one time.
261         * @see #getMaxTotal
262         * @see #setMaxTotal
263         */
264        public static final int DEFAULT_MAX_TOTAL  = -1;
265    
266        /**
267         * The default "when exhausted action" for the pool.
268         * @see #WHEN_EXHAUSTED_BLOCK
269         * @see #WHEN_EXHAUSTED_FAIL
270         * @see #WHEN_EXHAUSTED_GROW
271         * @see #setWhenExhaustedAction
272         */
273        public static final byte DEFAULT_WHEN_EXHAUSTED_ACTION = WHEN_EXHAUSTED_BLOCK;
274    
275        /**
276         * The default maximum amount of time (in milliseconds) the
277         * {@link #borrowObject} method should block before throwing
278         * an exception when the pool is exhausted and the
279         * {@link #getWhenExhaustedAction "when exhausted" action} is
280         * {@link #WHEN_EXHAUSTED_BLOCK}.
281         * @see #getMaxWait
282         * @see #setMaxWait
283         */
284        public static final long DEFAULT_MAX_WAIT = -1L;
285    
286        /**
287         * The default "test on borrow" value.
288         * @see #getTestOnBorrow
289         * @see #setTestOnBorrow
290         */
291        public static final boolean DEFAULT_TEST_ON_BORROW = false;
292    
293        /**
294         * The default "test on return" value.
295         * @see #getTestOnReturn
296         * @see #setTestOnReturn
297         */
298        public static final boolean DEFAULT_TEST_ON_RETURN = false;
299    
300        /**
301         * The default "test while idle" value.
302         * @see #getTestWhileIdle
303         * @see #setTestWhileIdle
304         * @see #getTimeBetweenEvictionRunsMillis
305         * @see #setTimeBetweenEvictionRunsMillis
306         */
307        public static final boolean DEFAULT_TEST_WHILE_IDLE = false;
308    
309        /**
310         * The default "time between eviction runs" value.
311         * @see #getTimeBetweenEvictionRunsMillis
312         * @see #setTimeBetweenEvictionRunsMillis
313         */
314        public static final long DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS = -1L;
315    
316        /**
317         * The default number of objects to examine per run in the
318         * idle object evictor.
319         * @see #getNumTestsPerEvictionRun
320         * @see #setNumTestsPerEvictionRun
321         * @see #getTimeBetweenEvictionRunsMillis
322         * @see #setTimeBetweenEvictionRunsMillis
323         */
324        public static final int DEFAULT_NUM_TESTS_PER_EVICTION_RUN = 3;
325    
326        /**
327         * The default value for {@link #getMinEvictableIdleTimeMillis}.
328         * @see #getMinEvictableIdleTimeMillis
329         * @see #setMinEvictableIdleTimeMillis
330         */
331        public static final long DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS = 1000L * 60L * 30L;
332    
333        /**
334         * The default minimum level of idle objects in the pool.
335         * @since Pool 1.3
336         * @see #setMinIdle
337         * @see #getMinIdle
338         */
339        public static final int DEFAULT_MIN_IDLE = 0;
340    
341        /**
342         * The default LIFO status. True means that borrowObject returns the
343         * most recently used ("last in") idle object in a pool (if there are
344         * idle instances available).  False means that pools behave as FIFO
345         * queues - objects are taken from idle object pools in the order that
346         * they are returned.
347         * @see #setLifo
348         */
349        public static final boolean DEFAULT_LIFO = true;
350    
351        //--- constructors -----------------------------------------------
352    
353        /**
354         * Create a new <code>GenericKeyedObjectPool</code> with no factory.
355         *
356         * @see #GenericKeyedObjectPool(KeyedPoolableObjectFactory)
357         * @see #setFactory(KeyedPoolableObjectFactory)
358         */
359        public GenericKeyedObjectPool() {
360            this(null, DEFAULT_MAX_ACTIVE, DEFAULT_WHEN_EXHAUSTED_ACTION, DEFAULT_MAX_WAIT, DEFAULT_MAX_IDLE, 
361                    DEFAULT_TEST_ON_BORROW, DEFAULT_TEST_ON_RETURN, DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,
362                    DEFAULT_NUM_TESTS_PER_EVICTION_RUN, DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS, DEFAULT_TEST_WHILE_IDLE);
363        }
364    
365        /**
366         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
367         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy
368         * objects if not <code>null</code>
369         */
370        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory) {
371            this(factory, DEFAULT_MAX_ACTIVE, DEFAULT_WHEN_EXHAUSTED_ACTION, DEFAULT_MAX_WAIT, DEFAULT_MAX_IDLE,
372                    DEFAULT_TEST_ON_BORROW, DEFAULT_TEST_ON_RETURN, DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS,
373                    DEFAULT_NUM_TESTS_PER_EVICTION_RUN, DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS, DEFAULT_TEST_WHILE_IDLE);
374        }
375    
376        /**
377         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
378         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
379         * if not <code>null</code>
380         * @param config a non-<code>null</code> {@link GenericKeyedObjectPool.Config} describing the configuration
381         */
382        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, GenericKeyedObjectPool.Config config) {
383            this(factory, config.maxActive, config.whenExhaustedAction, config.maxWait, config.maxIdle, config.maxTotal,
384                    config.minIdle, config.testOnBorrow, config.testOnReturn, config.timeBetweenEvictionRunsMillis,
385                    config.numTestsPerEvictionRun, config.minEvictableIdleTimeMillis, config.testWhileIdle, config.lifo);
386        }
387    
388        /**
389         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
390         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
391         * if not <code>null</code>
392         * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
393         */
394        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive) {
395            this(factory,maxActive, DEFAULT_WHEN_EXHAUSTED_ACTION, DEFAULT_MAX_WAIT, DEFAULT_MAX_IDLE,
396                    DEFAULT_TEST_ON_BORROW, DEFAULT_TEST_ON_RETURN, DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS, 
397                    DEFAULT_NUM_TESTS_PER_EVICTION_RUN, DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS, DEFAULT_TEST_WHILE_IDLE);
398        }
399    
400        /**
401         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
402         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
403         * if not <code>null</code>
404         * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
405         * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
406         * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
407         *  <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
408         */
409        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
410                long maxWait) {
411            this(factory, maxActive, whenExhaustedAction, maxWait, DEFAULT_MAX_IDLE, DEFAULT_TEST_ON_BORROW,
412                    DEFAULT_TEST_ON_RETURN, DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS, DEFAULT_NUM_TESTS_PER_EVICTION_RUN,
413                    DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS, DEFAULT_TEST_WHILE_IDLE);
414        }
415    
416        /**
417         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
418         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
419         * if not <code>null</code>
420         * @param maxActive the maximum number of objects that can be borrowed from me at one time (see {@link #setMaxActive})
421         * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
422         * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
423         * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
424         * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject}
425         * method (see {@link #setTestOnBorrow})
426         * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject}
427         * method (see {@link #setTestOnReturn})
428         */
429        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
430                long maxWait, boolean testOnBorrow, boolean testOnReturn) {
431            this(factory, maxActive, whenExhaustedAction, maxWait, DEFAULT_MAX_IDLE,testOnBorrow,testOnReturn,
432                    DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS, DEFAULT_NUM_TESTS_PER_EVICTION_RUN,
433                    DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS, DEFAULT_TEST_WHILE_IDLE);
434        }
435    
436        /**
437         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
438         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
439         * if not <code>null</code>
440         * @param maxActive the maximum number of objects that can be borrowed from me at one time
441         * (see {@link #setMaxActive})
442         * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
443         * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
444         * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
445         * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
446         */
447        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
448                long maxWait, int maxIdle) {
449            this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, DEFAULT_TEST_ON_BORROW, DEFAULT_TEST_ON_RETURN,
450                    DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS, DEFAULT_NUM_TESTS_PER_EVICTION_RUN,
451                    DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS, DEFAULT_TEST_WHILE_IDLE);
452        }
453    
454        /**
455         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
456         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
457         * if not <code>null</code>
458         * @param maxActive the maximum number of objects that can be borrowed from me at one time
459         * (see {@link #setMaxActive})
460         * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
461         * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
462         * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #getMaxWait})
463         * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
464         * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject}
465         * method (see {@link #setTestOnBorrow})
466         * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject}
467         * method (see {@link #setTestOnReturn})
468         */
469        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
470                long maxWait, int maxIdle, boolean testOnBorrow, boolean testOnReturn) {
471            this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, testOnBorrow, testOnReturn,
472                    DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS, DEFAULT_NUM_TESTS_PER_EVICTION_RUN,
473                    DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS, DEFAULT_TEST_WHILE_IDLE);
474        }
475    
476        /**
477         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
478         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
479         * if not <code>null</code>
480         * @param maxActive the maximum number of objects that can be borrowed from me at one time
481         * (see {@link #setMaxActive})
482         * @param whenExhaustedAction the action to take when the pool is exhausted 
483         * (see {@link #setWhenExhaustedAction})
484         * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
485         * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
486         * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
487         * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject}
488         * method (see {@link #setTestOnBorrow})
489         * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject}
490         * method (see {@link #setTestOnReturn})
491         * @param timeBetweenEvictionRunsMillis the amount of time (in milliseconds) to sleep between examining idle
492         * objects for eviction (see {@link #setTimeBetweenEvictionRunsMillis})
493         * @param numTestsPerEvictionRun the number of idle objects to examine per run within the idle object eviction
494         * thread (if any) (see {@link #setNumTestsPerEvictionRun})
495         * @param minEvictableIdleTimeMillis the minimum number of milliseconds an object can sit idle in the pool before
496         * it is eligible for eviction (see {@link #setMinEvictableIdleTimeMillis})
497         * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any
498         * (see {@link #setTestWhileIdle})
499         */
500        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
501                long maxWait, int maxIdle, boolean testOnBorrow, boolean testOnReturn, long timeBetweenEvictionRunsMillis,
502                int numTestsPerEvictionRun, long minEvictableIdleTimeMillis, boolean testWhileIdle) {
503            this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, GenericKeyedObjectPool.DEFAULT_MAX_TOTAL,
504                    testOnBorrow, testOnReturn, timeBetweenEvictionRunsMillis, numTestsPerEvictionRun,
505                    minEvictableIdleTimeMillis, testWhileIdle);
506        }
507    
508        /**
509         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
510         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
511         * if not <code>null</code>
512         * @param maxActive the maximum number of objects that can be borrowed from me at one time
513         * (see {@link #setMaxActive})
514         * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
515         * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
516         * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
517         * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
518         * @param maxTotal the maximum number of objects that can exists at one time (see {@link #setMaxTotal})
519         * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject}
520         * method (see {@link #setTestOnBorrow})
521         * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject}
522         * method (see {@link #setTestOnReturn})
523         * @param timeBetweenEvictionRunsMillis the amount of time (in milliseconds) to sleep between examining idle
524         * objects for eviction (see {@link #setTimeBetweenEvictionRunsMillis})
525         * @param numTestsPerEvictionRun the number of idle objects to examine per run within the idle object eviction
526         * thread (if any) (see {@link #setNumTestsPerEvictionRun})
527         * @param minEvictableIdleTimeMillis the minimum number of milliseconds an object can sit idle in the pool
528         * before it is eligible for eviction (see {@link #setMinEvictableIdleTimeMillis})
529         * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any
530         * (see {@link #setTestWhileIdle})
531         */
532        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
533                long maxWait, int maxIdle, int maxTotal, boolean testOnBorrow, boolean testOnReturn,
534                long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis,
535                boolean testWhileIdle) {
536            this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, maxTotal,
537                    GenericKeyedObjectPool.DEFAULT_MIN_IDLE, testOnBorrow, testOnReturn, timeBetweenEvictionRunsMillis,
538                    numTestsPerEvictionRun, minEvictableIdleTimeMillis, testWhileIdle);
539        }
540    
541        /**
542         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
543         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
544         * if not <code>null</code>
545         * @param maxActive the maximum number of objects that can be borrowed at one time (see {@link #setMaxActive})
546         * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
547         * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
548         * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
549         * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
550         * @param maxTotal the maximum number of objects that can exists at one time (see {@link #setMaxTotal})
551         * @param minIdle the minimum number of idle objects to have in the pool at any one time (see {@link #setMinIdle})
552         * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject}
553         * method (see {@link #setTestOnBorrow})
554         * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject}
555         * method (see {@link #setTestOnReturn})
556         * @param timeBetweenEvictionRunsMillis the amount of time (in milliseconds) to sleep between examining idle
557         * objects
558         * for eviction (see {@link #setTimeBetweenEvictionRunsMillis})
559         * @param numTestsPerEvictionRun the number of idle objects to examine per run within the idle object eviction
560         * thread (if any) (see {@link #setNumTestsPerEvictionRun})
561         * @param minEvictableIdleTimeMillis the minimum number of milliseconds an object can sit idle in the pool before
562         * it is eligible for eviction (see {@link #setMinEvictableIdleTimeMillis})
563         * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any
564         * (see {@link #setTestWhileIdle})
565         * @since Pool 1.3
566         */
567        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
568                long maxWait, int maxIdle, int maxTotal, int minIdle, boolean testOnBorrow, boolean testOnReturn,
569                long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis,
570                boolean testWhileIdle) {
571            this(factory, maxActive, whenExhaustedAction, maxWait, maxIdle, maxTotal, minIdle, testOnBorrow, testOnReturn,
572                    timeBetweenEvictionRunsMillis, numTestsPerEvictionRun, minEvictableIdleTimeMillis, testWhileIdle,
573                    DEFAULT_LIFO);
574        }
575    
576        /**
577         * Create a new <code>GenericKeyedObjectPool</code> using the specified values.
578         * @param factory the <code>KeyedPoolableObjectFactory</code> to use to create, validate, and destroy objects
579         * if not <code>null</code>
580         * @param maxActive the maximum number of objects that can be borrowed at one time
581         *  (see {@link #setMaxActive})
582         * @param whenExhaustedAction the action to take when the pool is exhausted (see {@link #setWhenExhaustedAction})
583         * @param maxWait the maximum amount of time to wait for an idle object when the pool is exhausted and
584         * <code>whenExhaustedAction</code> is {@link #WHEN_EXHAUSTED_BLOCK} (otherwise ignored) (see {@link #setMaxWait})
585         * @param maxIdle the maximum number of idle objects in my pool (see {@link #setMaxIdle})
586         * @param maxTotal the maximum number of objects that can exists at one time (see {@link #setMaxTotal})
587         * @param minIdle the minimum number of idle objects to have in the pool at any one time (see {@link #setMinIdle})
588         * @param testOnBorrow whether or not to validate objects before they are returned by the {@link #borrowObject}
589         * method (see {@link #setTestOnBorrow})
590         * @param testOnReturn whether or not to validate objects after they are returned to the {@link #returnObject}
591         * method (see {@link #setTestOnReturn})
592         * @param timeBetweenEvictionRunsMillis the amount of time (in milliseconds) to sleep between examining idle
593         * objects for eviction (see {@link #setTimeBetweenEvictionRunsMillis})
594         * @param numTestsPerEvictionRun the number of idle objects to examine per run within the idle object eviction
595         * thread (if any) (see {@link #setNumTestsPerEvictionRun})
596         * @param minEvictableIdleTimeMillis the minimum number of milliseconds an object can sit idle in the pool before
597         * it is eligible for eviction (see {@link #setMinEvictableIdleTimeMillis})
598         * @param testWhileIdle whether or not to validate objects in the idle object eviction thread, if any
599         * (see {@link #setTestWhileIdle})
600         * @param lifo whether or not the pools behave as LIFO (last in first out) queues (see {@link #setLifo})
601         * @since Pool 1.4
602         */
603        public GenericKeyedObjectPool(KeyedPoolableObjectFactory factory, int maxActive, byte whenExhaustedAction,
604                long maxWait, int maxIdle, int maxTotal, int minIdle, boolean testOnBorrow, boolean testOnReturn,
605                long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis,
606                boolean testWhileIdle, boolean lifo) {
607            _factory = factory;
608            _maxActive = maxActive;
609            _lifo = lifo;
610            switch (whenExhaustedAction) {
611                case WHEN_EXHAUSTED_BLOCK:
612                case WHEN_EXHAUSTED_FAIL:
613                case WHEN_EXHAUSTED_GROW:
614                    _whenExhaustedAction = whenExhaustedAction;
615                    break;
616                default:
617                    throw new IllegalArgumentException("whenExhaustedAction " + whenExhaustedAction + " not recognized.");
618            }
619            _maxWait = maxWait;
620            _maxIdle = maxIdle;
621            _maxTotal = maxTotal;
622            _minIdle = minIdle;
623            _testOnBorrow = testOnBorrow;
624            _testOnReturn = testOnReturn;
625            _timeBetweenEvictionRunsMillis = timeBetweenEvictionRunsMillis;
626            _numTestsPerEvictionRun = numTestsPerEvictionRun;
627            _minEvictableIdleTimeMillis = minEvictableIdleTimeMillis;
628            _testWhileIdle = testWhileIdle;
629    
630            _poolMap = new HashMap();
631            _poolList = new CursorableLinkedList();
632    
633            startEvictor(_timeBetweenEvictionRunsMillis);
634        }
635    
636        //--- public methods ---------------------------------------------
637    
638        //--- configuration methods --------------------------------------
639    
640        /**
641         * Returns the cap on the number of object instances allocated by the pool
642         * (checked out or idle),  per key.
643         * A negative value indicates no limit.
644         *
645         * @return the cap on the number of active instances per key.
646         * @see #setMaxActive
647         */
648        public synchronized int getMaxActive() {
649            return _maxActive;
650        }
651    
652        /**
653         * Sets the cap on the number of object instances managed by the pool per key.
654         * @param maxActive The cap on the number of object instances per key.
655         * Use a negative value for no limit.
656         *
657         * @see #getMaxActive
658         */
659        public synchronized void setMaxActive(int maxActive) {
660            _maxActive = maxActive;
661            allocate();
662        }
663    
664        /**
665         * Returns the overall maximum number of objects (across pools) that can
666         * exist at one time. A negative value indicates no limit.
667         * @return the maximum number of instances in circulation at one time.
668         * @see #setMaxTotal
669         */
670        public synchronized int getMaxTotal() {
671            return _maxTotal;
672        }
673    
674        /**
675         * Sets the cap on the total number of instances from all pools combined.
676         * When <code>maxTotal</code> is set to a
677         * positive value and {@link #borrowObject borrowObject} is invoked
678         * when at the limit with no idle instances available, an attempt is made to
679         * create room by clearing the oldest 15% of the elements from the keyed
680         * pools.
681         *
682         * @param maxTotal The cap on the total number of instances across pools.
683         * Use a negative value for no limit.
684         * @see #getMaxTotal
685         */
686        public synchronized void setMaxTotal(int maxTotal) {
687            _maxTotal = maxTotal;
688            allocate();
689        }
690    
691        /**
692         * Returns the action to take when the {@link #borrowObject} method
693         * is invoked when the pool is exhausted (the maximum number
694         * of "active" objects has been reached).
695         *
696         * @return one of {@link #WHEN_EXHAUSTED_BLOCK},
697         * {@link #WHEN_EXHAUSTED_FAIL} or {@link #WHEN_EXHAUSTED_GROW}
698         * @see #setWhenExhaustedAction
699         */
700        public synchronized byte getWhenExhaustedAction() {
701            return _whenExhaustedAction;
702        }
703    
704        /**
705         * Sets the action to take when the {@link #borrowObject} method
706         * is invoked when the pool is exhausted (the maximum number
707         * of "active" objects has been reached).
708         *
709         * @param whenExhaustedAction the action code, which must be one of
710         *        {@link #WHEN_EXHAUSTED_BLOCK}, {@link #WHEN_EXHAUSTED_FAIL},
711         *        or {@link #WHEN_EXHAUSTED_GROW}
712         * @see #getWhenExhaustedAction
713         */
714        public synchronized void setWhenExhaustedAction(byte whenExhaustedAction) {
715            switch(whenExhaustedAction) {
716                case WHEN_EXHAUSTED_BLOCK:
717                case WHEN_EXHAUSTED_FAIL:
718                case WHEN_EXHAUSTED_GROW:
719                    _whenExhaustedAction = whenExhaustedAction;
720                    allocate();
721                    break;
722                default:
723                    throw new IllegalArgumentException("whenExhaustedAction " + whenExhaustedAction + " not recognized.");
724            }
725        }
726    
727    
728        /**
729         * Returns the maximum amount of time (in milliseconds) the
730         * {@link #borrowObject} method should block before throwing
731         * an exception when the pool is exhausted and the
732         * {@link #setWhenExhaustedAction "when exhausted" action} is
733         * {@link #WHEN_EXHAUSTED_BLOCK}.
734         *
735         * When less than or equal to 0, the {@link #borrowObject} method
736         * may block indefinitely.
737         *
738         * @return the maximum number of milliseconds borrowObject will block.
739         * @see #setMaxWait
740         * @see #setWhenExhaustedAction
741         * @see #WHEN_EXHAUSTED_BLOCK
742         */
743        public synchronized long getMaxWait() {
744            return _maxWait;
745        }
746    
747        /**
748         * Sets the maximum amount of time (in milliseconds) the
749         * {@link #borrowObject} method should block before throwing
750         * an exception when the pool is exhausted and the
751         * {@link #setWhenExhaustedAction "when exhausted" action} is
752         * {@link #WHEN_EXHAUSTED_BLOCK}.
753         *
754         * When less than or equal to 0, the {@link #borrowObject} method
755         * may block indefinitely.
756         *
757         * @param maxWait the maximum number of milliseconds borrowObject will block or negative for indefinitely.
758         * @see #getMaxWait
759         * @see #setWhenExhaustedAction
760         * @see #WHEN_EXHAUSTED_BLOCK
761         */
762        public synchronized void setMaxWait(long maxWait) {
763            _maxWait = maxWait;
764        }
765    
766        /**
767         * Returns the cap on the number of "idle" instances per key.
768         * @return the maximum number of "idle" instances that can be held
769         * in a given keyed pool.
770         * @see #setMaxIdle
771         */
772        public synchronized int getMaxIdle() {
773            return _maxIdle;
774        }
775    
776        /**
777         * Sets the cap on the number of "idle" instances in the pool.
778         * If maxIdle is set too low on heavily loaded systems it is possible you
779         * will see objects being destroyed and almost immediately new objects
780         * being created. This is a result of the active threads momentarily
781         * returning objects faster than they are requesting them them, causing the
782         * number of idle objects to rise above maxIdle. The best value for maxIdle
783         * for heavily loaded system will vary but the default is a good starting
784         * point.
785         * @param maxIdle the maximum number of "idle" instances that can be held
786         * in a given keyed pool. Use a negative value for no limit.
787         * @see #getMaxIdle
788         * @see #DEFAULT_MAX_IDLE
789         */
790        public synchronized void setMaxIdle(int maxIdle) {
791            _maxIdle = maxIdle;
792            allocate();
793        }
794    
795        /**
796         * Sets the minimum number of idle objects to maintain in each of the keyed
797         * pools. This setting has no effect unless
798         * <code>timeBetweenEvictionRunsMillis > 0</code> and attempts to ensure
799         * that each pool has the required minimum number of instances are only
800         * made during idle object eviction runs.
801         * @param poolSize - The minimum size of the each keyed pool
802         * @since Pool 1.3
803         * @see #getMinIdle
804         * @see #setTimeBetweenEvictionRunsMillis
805         */
806        public synchronized void setMinIdle(int poolSize) {
807            _minIdle = poolSize;
808        }
809    
810        /**
811         * Returns the minimum number of idle objects to maintain in each of the keyed
812         * pools. This setting has no effect unless
813         * <code>timeBetweenEvictionRunsMillis > 0</code> and attempts to ensure
814         * that each pool has the required minimum number of instances are only
815         * made during idle object eviction runs.
816         * @return minimum size of the each keyed pool
817         * @since Pool 1.3
818         * @see #setTimeBetweenEvictionRunsMillis
819         */
820        public synchronized int getMinIdle() {
821            return _minIdle;
822        }
823    
824        /**
825         * When <code>true</code>, objects will be
826         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
827         * before being returned by the {@link #borrowObject}
828         * method.  If the object fails to validate,
829         * it will be dropped from the pool, and we will attempt
830         * to borrow another.
831         *
832         * @return <code>true</code> if objects are validated before being borrowed.
833         * @see #setTestOnBorrow
834         */
835        public boolean getTestOnBorrow() {
836            return _testOnBorrow;
837        }
838    
839        /**
840         * When <code>true</code>, objects will be
841         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
842         * before being returned by the {@link #borrowObject}
843         * method.  If the object fails to validate,
844         * it will be dropped from the pool, and we will attempt
845         * to borrow another.
846         *
847         * @param testOnBorrow whether object should be validated before being returned by borrowObject.
848         * @see #getTestOnBorrow
849         */
850        public void setTestOnBorrow(boolean testOnBorrow) {
851            _testOnBorrow = testOnBorrow;
852        }
853    
854        /**
855         * When <code>true</code>, objects will be
856         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
857         * before being returned to the pool within the
858         * {@link #returnObject}.
859         *
860         * @return <code>true</code> when objects will be validated before being returned.
861         * @see #setTestOnReturn
862         */
863        public boolean getTestOnReturn() {
864            return _testOnReturn;
865        }
866    
867        /**
868         * When <code>true</code>, objects will be
869         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
870         * before being returned to the pool within the
871         * {@link #returnObject}.
872         *
873         * @param testOnReturn <code>true</code> so objects will be validated before being returned.
874         * @see #getTestOnReturn
875         */
876        public void setTestOnReturn(boolean testOnReturn) {
877            _testOnReturn = testOnReturn;
878        }
879    
880        /**
881         * Returns the number of milliseconds to sleep between runs of the
882         * idle object evictor thread.
883         * When non-positive, no idle object evictor thread will be
884         * run.
885         *
886         * @return milliseconds to sleep between evictor runs.
887         * @see #setTimeBetweenEvictionRunsMillis
888         */
889        public synchronized long getTimeBetweenEvictionRunsMillis() {
890            return _timeBetweenEvictionRunsMillis;
891        }
892    
893        /**
894         * Sets the number of milliseconds to sleep between runs of the
895         * idle object evictor thread.
896         * When non-positive, no idle object evictor thread will be
897         * run.
898         *
899         * @param timeBetweenEvictionRunsMillis milliseconds to sleep between evictor runs.
900         * @see #getTimeBetweenEvictionRunsMillis
901         */
902        public synchronized void setTimeBetweenEvictionRunsMillis(long timeBetweenEvictionRunsMillis) {
903            _timeBetweenEvictionRunsMillis = timeBetweenEvictionRunsMillis;
904            startEvictor(_timeBetweenEvictionRunsMillis);
905        }
906    
907        /**
908         * Returns the max number of objects to examine during each run of the
909         * idle object evictor thread (if any).
910         *
911         * @return number of objects to examine each eviction run.
912         * @see #setNumTestsPerEvictionRun
913         * @see #setTimeBetweenEvictionRunsMillis
914         */
915        public synchronized int getNumTestsPerEvictionRun() {
916            return _numTestsPerEvictionRun;
917        }
918    
919        /**
920         * Sets the max number of objects to examine during each run of the
921         * idle object evictor thread (if any).
922         * <p>
923         * When a negative value is supplied, 
924         * <code>ceil({@link #getNumIdle()})/abs({@link #getNumTestsPerEvictionRun})</code>
925         * tests will be run.  I.e., when the value is <code>-n</code>, roughly one <code>n</code>th of the
926         * idle objects will be tested per run.  When the value is positive, the number of tests
927         * actually performed in each run will be the minimum of this value and the number of instances
928         * idle in the pools.
929         *
930         * @param numTestsPerEvictionRun number of objects to examine each eviction run.
931         * @see #setNumTestsPerEvictionRun
932         * @see #setTimeBetweenEvictionRunsMillis
933         */
934        public synchronized void setNumTestsPerEvictionRun(int numTestsPerEvictionRun) {
935            _numTestsPerEvictionRun = numTestsPerEvictionRun;
936        }
937    
938        /**
939         * Returns the minimum amount of time an object may sit idle in the pool
940         * before it is eligible for eviction by the idle object evictor
941         * (if any).
942         *
943         * @return minimum amount of time an object may sit idle in the pool before it is eligible for eviction.
944         * @see #setMinEvictableIdleTimeMillis
945         * @see #setTimeBetweenEvictionRunsMillis
946         */
947        public synchronized long getMinEvictableIdleTimeMillis() {
948            return _minEvictableIdleTimeMillis;
949        }
950    
951        /**
952         * Sets the minimum amount of time an object may sit idle in the pool
953         * before it is eligible for eviction by the idle object evictor
954         * (if any).
955         * When non-positive, no objects will be evicted from the pool
956         * due to idle time alone.
957         *
958         * @param minEvictableIdleTimeMillis minimum amount of time an object may sit idle in the pool before
959         * it is eligible for eviction.
960         * @see #getMinEvictableIdleTimeMillis
961         * @see #setTimeBetweenEvictionRunsMillis
962         */
963        public synchronized void setMinEvictableIdleTimeMillis(long minEvictableIdleTimeMillis) {
964            _minEvictableIdleTimeMillis = minEvictableIdleTimeMillis;
965        }
966    
967        /**
968         * When <code>true</code>, objects will be
969         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
970         * by the idle object evictor (if any).  If an object
971         * fails to validate, it will be dropped from the pool.
972         *
973         * @return <code>true</code> when objects are validated when borrowed.
974         * @see #setTestWhileIdle
975         * @see #setTimeBetweenEvictionRunsMillis
976         */
977        public synchronized boolean getTestWhileIdle() {
978            return _testWhileIdle;
979        }
980    
981        /**
982         * When <code>true</code>, objects will be
983         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
984         * by the idle object evictor (if any).  If an object
985         * fails to validate, it will be dropped from the pool.
986         *
987         * @param testWhileIdle <code>true</code> so objects are validated when borrowed.
988         * @see #getTestWhileIdle
989         * @see #setTimeBetweenEvictionRunsMillis
990         */
991        public synchronized void setTestWhileIdle(boolean testWhileIdle) {
992            _testWhileIdle = testWhileIdle;
993        }
994    
995        /**
996         * Sets the configuration.
997         * @param conf the new configuration to use.
998         * @see GenericKeyedObjectPool.Config
999         */
1000        public synchronized void setConfig(GenericKeyedObjectPool.Config conf) {
1001            setMaxIdle(conf.maxIdle);
1002            setMaxActive(conf.maxActive);
1003            setMaxTotal(conf.maxTotal);
1004            setMinIdle(conf.minIdle);
1005            setMaxWait(conf.maxWait);
1006            setWhenExhaustedAction(conf.whenExhaustedAction);
1007            setTestOnBorrow(conf.testOnBorrow);
1008            setTestOnReturn(conf.testOnReturn);
1009            setTestWhileIdle(conf.testWhileIdle);
1010            setNumTestsPerEvictionRun(conf.numTestsPerEvictionRun);
1011            setMinEvictableIdleTimeMillis(conf.minEvictableIdleTimeMillis);
1012            setTimeBetweenEvictionRunsMillis(conf.timeBetweenEvictionRunsMillis);
1013        }
1014    
1015        /**
1016         * Whether or not the idle object pools act as LIFO queues. True means
1017         * that borrowObject returns the most recently used ("last in") idle object
1018         * in a pool (if there are idle instances available).  False means that
1019         * the pools behave as FIFO queues - objects are taken from idle object
1020         * pools in the order that they are returned.
1021         *
1022         * @return <code>true</code> if the pools are configured to act as LIFO queues
1023         * @since 1.4
1024         */
1025         public synchronized boolean getLifo() {
1026             return _lifo;
1027         }
1028    
1029         /**
1030          * Sets the LIFO property of the pools. True means that borrowObject returns
1031          * the most recently used ("last in") idle object in a pool (if there are
1032          * idle instances available).  False means that the pools behave as FIFO
1033          * queues - objects are taken from idle object pools in the order that
1034          * they are returned.
1035          *
1036          * @param lifo the new value for the lifo property
1037          * @since 1.4
1038          */
1039         public synchronized void setLifo(boolean lifo) {
1040             this._lifo = lifo;
1041         }
1042    
1043        //-- ObjectPool methods ------------------------------------------
1044    
1045        /**
1046         * <p>Borrows an object from the keyed pool associated with the given key.</p>
1047         * 
1048         * <p>If there is an idle instance available in the pool associated with the given key, then
1049         * either the most-recently returned (if {@link #getLifo() lifo} == true) or "oldest" (lifo == false)
1050         * instance sitting idle in the pool will be activated and returned.  If activation fails, or
1051         * {@link #getTestOnBorrow() testOnBorrow} is set to true and validation fails, the instance is destroyed and the
1052         * next available instance is examined.  This continues until either a valid instance is returned or there
1053         * are no more idle instances available.</p>
1054         * 
1055         * <p>If there are no idle instances available in the pool associated with the given key, behavior
1056         * depends on the {@link #getMaxActive() maxActive}, {@link #getMaxTotal() maxTotal}, and (if applicable)
1057         * {@link #getWhenExhaustedAction() whenExhaustedAction} and {@link #getMaxWait() maxWait} properties. If the
1058         * number of instances checked out from the pool under the given key is less than <code>maxActive</code> and
1059         * the total number of instances in circulation (under all keys) is less than <code>maxTotal</code>, a new instance
1060         * is created, activated and (if applicable) validated and returned to the caller.</p>
1061         * 
1062         * <p>If the associated keyed pool is exhausted (no available idle instances and no capacity to create new ones),
1063         * this method will either block ({@link #WHEN_EXHAUSTED_BLOCK}), throw a <code>NoSuchElementException</code>
1064         * ({@link #WHEN_EXHAUSTED_FAIL}), or grow ({@link #WHEN_EXHAUSTED_GROW} - ignoring maxActive, maxTotal properties).
1065         * The length of time that this method will block when <code>whenExhaustedAction == WHEN_EXHAUSTED_BLOCK</code>
1066         * is determined by the {@link #getMaxWait() maxWait} property.</p>
1067         * 
1068         * <p>When the pool is exhausted, multiple calling threads may be simultaneously blocked waiting for instances
1069         * to become available.  As of pool 1.5, a "fairness" algorithm has been implemented to ensure that threads receive
1070         * available instances in request arrival order.</p>
1071         * 
1072         * @param key pool key
1073         * @return object instance from the keyed pool
1074         * @throws NoSuchElementException if a keyed object instance cannot be returned.
1075         */
1076         public Object borrowObject(Object key) throws Exception {
1077            long starttime = System.currentTimeMillis();
1078            Latch latch = new Latch(key);
1079            byte whenExhaustedAction;
1080            long maxWait;
1081            synchronized (this) {
1082                // Get local copy of current config. Can't sync when used later as
1083                // it can result in a deadlock. Has the added advantage that config
1084                // is consistent for entire method execution
1085                whenExhaustedAction = _whenExhaustedAction;
1086                maxWait = _maxWait;
1087    
1088                // Add this request to the queue
1089                _allocationQueue.add(latch);
1090    
1091                // Work the allocation queue, allocating idle instances and
1092                // instance creation permits in request arrival order
1093                allocate();
1094            }
1095    
1096            for(;;) {
1097                synchronized (this) {
1098                    assertOpen();
1099                }
1100                // If no object was allocated
1101                if (null == latch.getPair()) {
1102                    // Check to see if we were allowed to create one
1103                    if (latch.mayCreate()) {
1104                        // allow new object to be created
1105                    } else {
1106                        // the pool is exhausted
1107                        switch(whenExhaustedAction) {
1108                            case WHEN_EXHAUSTED_GROW:
1109                                // allow new object to be created
1110                                synchronized (this) {
1111                                    // Make sure allocate hasn't already assigned an object
1112                                    // in a different thread
1113                                    if (latch.getPair() == null) {
1114                                        _allocationQueue.remove(latch);
1115                                        latch.getPool().incrementInternalProcessingCount();
1116                                    }
1117                                }
1118                            break;
1119                            case WHEN_EXHAUSTED_FAIL:
1120                                synchronized (this) {
1121                                    // Make sure allocate hasn't already assigned an object
1122                                    // in a different thread
1123                                    if (latch.getPair() != null) {
1124                                        break;
1125                                    }
1126                                    _allocationQueue.remove(latch);
1127                                }
1128                                throw new NoSuchElementException("Pool exhausted");
1129                            case WHEN_EXHAUSTED_BLOCK:
1130                                try {
1131                                    synchronized (latch) {
1132                                        // Before we wait, make sure another thread didn't allocate us an object
1133                                        if (latch.getPair() == null) {
1134                                            if (maxWait <= 0) {
1135                                                latch.wait();
1136                                            } else {
1137                                                // this code may be executed again after a notify then continue cycle
1138                                                // so, need to calculate the amount of time to wait
1139                                                final long elapsed = (System.currentTimeMillis() - starttime);
1140                                                final long waitTime = maxWait - elapsed;
1141                                                if (waitTime > 0)
1142                                                {
1143                                                    latch.wait(waitTime);
1144                                                }
1145                                            }
1146                                        } else {
1147                                            break;
1148                                        }
1149                                    }
1150                                } catch(InterruptedException e) {
1151                                    Thread.currentThread().interrupt();
1152                                    throw e;
1153                                    }
1154                                if (maxWait > 0 && ((System.currentTimeMillis() - starttime) >= maxWait)) {
1155                                    synchronized (this) {
1156                                        // Make sure allocate hasn't already assigned an object
1157                                        // in a different thread
1158                                        if (latch.getPair() == null) {
1159                                            _allocationQueue.remove(latch);
1160                                        } else {
1161                                            break;
1162                                        }
1163                                    }
1164                                    throw new NoSuchElementException("Timeout waiting for idle object");
1165                                } else {
1166                                    continue; // keep looping
1167                                }
1168                            default:
1169                                throw new IllegalArgumentException("whenExhaustedAction " + whenExhaustedAction +
1170                                        " not recognized.");
1171                        }
1172                    }
1173                }
1174    
1175                boolean newlyCreated = false;
1176                if (null == latch.getPair()) {
1177                    try {
1178                        Object obj = _factory.makeObject(key);
1179                        latch.setPair(new ObjectTimestampPair(obj));
1180                        newlyCreated = true;
1181                    } finally {
1182                        if (!newlyCreated) {
1183                            // object cannot be created
1184                            synchronized (this) {
1185                                latch.getPool().decrementInternalProcessingCount();
1186                                // No need to reset latch - about to throw exception
1187                                allocate();
1188                            }
1189                        }
1190                    }
1191                }
1192    
1193                // activate & validate the object
1194                try {
1195                    _factory.activateObject(key, latch.getPair().value);
1196                    if (_testOnBorrow && !_factory.validateObject(key, latch.getPair().value)) {
1197                        throw new Exception("ValidateObject failed");
1198                    }
1199                    synchronized (this) {
1200                        latch.getPool().decrementInternalProcessingCount();
1201                        latch.getPool().incrementActiveCount();
1202                    }
1203                    return latch.getPair().value;
1204                } catch (Throwable e) {
1205                    // object cannot be activated or is invalid
1206                    try {
1207                        _factory.destroyObject(key, latch.getPair().value);
1208                    } catch (Throwable e2) {
1209                        // cannot destroy broken object
1210                    }
1211                    synchronized (this) {
1212                        latch.getPool().decrementInternalProcessingCount();
1213                        latch.reset();
1214                        _allocationQueue.add(0, latch);
1215                        allocate();
1216                    }
1217                    if (newlyCreated) {
1218                        throw new NoSuchElementException(
1219                           "Could not create a validated object, cause: " +
1220                                e.getMessage());
1221                    }
1222                    else {
1223                        continue; // keep looping
1224                    }
1225                }
1226            }
1227        }
1228    
1229        /**
1230         * Allocate available instances to latches in the allocation queue.  Then
1231         * set _mayCreate to true for as many additional latches remaining in queue
1232         * as _maxActive allows for each key.
1233         */
1234        private void allocate() {
1235            boolean clearOldest = false;
1236    
1237            synchronized (this) {
1238                if (isClosed()) return;
1239                
1240                Iterator allocationQueueIter = _allocationQueue.iterator();
1241                
1242                while (allocationQueueIter.hasNext()) {
1243                    // First use any objects in the pool to clear the queue
1244                    Latch latch = (Latch) allocationQueueIter.next();
1245                    ObjectQueue pool = (ObjectQueue)(_poolMap.get(latch.getkey()));
1246                    if (null == pool) {
1247                        pool = new ObjectQueue();
1248                        _poolMap.put(latch.getkey(), pool);
1249                        _poolList.add(latch.getkey());
1250                    }
1251                    latch.setPool(pool);
1252                    if (!pool.queue.isEmpty()) {
1253                        allocationQueueIter.remove();
1254                        latch.setPair(
1255                                (ObjectTimestampPair) pool.queue.removeFirst());
1256                        pool.incrementInternalProcessingCount();
1257                        _totalIdle--;
1258                        synchronized (latch) {
1259                            latch.notify();
1260                        }
1261                        // Next item in queue
1262                        continue;
1263                    }
1264    
1265                    // If there is a totalMaxActive and we are at the limit then
1266                    // we have to make room
1267                    if ((_maxTotal > 0) &&
1268                            (_totalActive + _totalIdle + _totalInternalProcessing >= _maxTotal)) {
1269                        clearOldest = true;
1270                        break;
1271                    }
1272    
1273                    // Second utilise any spare capacity to create new objects
1274                    if ((_maxActive < 0 || pool.activeCount + pool.internalProcessingCount < _maxActive) &&
1275                            (_maxTotal < 0 || _totalActive + _totalIdle + _totalInternalProcessing < _maxTotal)) {
1276                        // allow new object to be created
1277                        allocationQueueIter.remove();
1278                        latch.setMayCreate(true);
1279                        pool.incrementInternalProcessingCount();
1280                        synchronized (latch) {
1281                            latch.notify();
1282                        }
1283                        // Next item in queue
1284                        continue;
1285                    }
1286    
1287                    // If there is no per-key limit and we reach this point we
1288                    // must have allocated all the objects we possibly can and there
1289                    // is no point looking at the rest of the allocation queue
1290                    if (_maxActive < 0) {
1291                        break;
1292                    }
1293                }
1294            }
1295            
1296            if (clearOldest) {
1297                /* Clear oldest calls factory methods so it must be called from
1298                 * outside the sync block.
1299                 * It also needs to be outside the sync block as it calls
1300                 * allocate(). If called inside the sync block, the call to
1301                 * allocate() would be able to enter the sync block (since the
1302                 * thread already has the lock) which may have unexpected,
1303                 * unpleasant results.
1304                 */
1305                clearOldest();
1306            }
1307        }
1308        
1309        /**
1310         * Clears any objects sitting idle in the pool by removing them from the
1311         * idle instance pool and then invoking the configured 
1312         * {@link KeyedPoolableObjectFactory#destroyObject(Object, Object)} method on
1313         * each idle instance.
1314         *  
1315         * <p> Implementation notes:
1316         * <ul><li>This method does not destroy or effect in any way instances that are
1317         * checked out when it is invoked.</li>
1318         * <li>Invoking this method does not prevent objects being
1319         * returned to the idle instance pool, even during its execution. It locks
1320         * the pool only during instance removal. Additional instances may be returned
1321         * while removed items are being destroyed.</li></ul></p>
1322         */
1323        public void clear() {
1324            Map toDestroy = new HashMap();
1325            synchronized (this) {
1326                for (Iterator it = _poolMap.keySet().iterator(); it.hasNext();) {
1327                    Object key = it.next();
1328                    ObjectQueue pool = (ObjectQueue)_poolMap.get(key);
1329                    // Copy objects to new list so pool.queue can be cleared inside
1330                    // the sync
1331                    List objects = new ArrayList();
1332                    objects.addAll(pool.queue);
1333                    toDestroy.put(key, objects);
1334                    it.remove();
1335                    _poolList.remove(key);
1336                    _totalIdle = _totalIdle - pool.queue.size();
1337                    _totalInternalProcessing =
1338                        _totalInternalProcessing + pool.queue.size();
1339                    pool.queue.clear();
1340                }
1341            }
1342            destroy(toDestroy);
1343        }
1344    
1345        /**
1346         * Clears oldest 15% of objects in pool.  The method sorts the
1347         * objects into a TreeMap and then iterates the first 15% for removal.
1348         * 
1349         * @since Pool 1.3
1350         */
1351        public void clearOldest() {
1352            // Map of objects to destroy my key
1353            final Map toDestroy = new HashMap();
1354    
1355            // build sorted map of idle objects
1356            final Map map = new TreeMap();
1357            synchronized (this) {
1358                for (Iterator keyiter = _poolMap.keySet().iterator(); keyiter.hasNext();) {
1359                    final Object key = keyiter.next();
1360                    final CursorableLinkedList list = ((ObjectQueue)_poolMap.get(key)).queue;
1361                    for (Iterator it = list.iterator(); it.hasNext();) {
1362                        // each item into the map uses the objectimestamppair object
1363                        // as the key.  It then gets sorted based on the timstamp field
1364                        // each value in the map is the parent list it belongs in.
1365                        map.put(it.next(), key);
1366                    }
1367                }
1368    
1369                // Now iterate created map and kill the first 15% plus one to account for zero
1370                Set setPairKeys = map.entrySet();
1371                int itemsToRemove = ((int) (map.size() * 0.15)) + 1;
1372    
1373                Iterator iter = setPairKeys.iterator();
1374                while (iter.hasNext() && itemsToRemove > 0) {
1375                    Map.Entry entry = (Map.Entry) iter.next();
1376                    // kind of backwards on naming.  In the map, each key is the objecttimestamppair
1377                    // because it has the ordering with the timestamp value.  Each value that the
1378                    // key references is the key of the list it belongs to.
1379                    Object key = entry.getValue();
1380                    ObjectTimestampPair pairTimeStamp = (ObjectTimestampPair) entry.getKey();
1381                    final CursorableLinkedList list =
1382                        ((ObjectQueue)(_poolMap.get(key))).queue;
1383                    list.remove(pairTimeStamp);
1384    
1385                    if (toDestroy.containsKey(key)) {
1386                        ((List)toDestroy.get(key)).add(pairTimeStamp);
1387                    } else {
1388                        List listForKey = new ArrayList();
1389                        listForKey.add(pairTimeStamp);
1390                        toDestroy.put(key, listForKey);
1391                    }
1392                    // if that was the last object for that key, drop that pool
1393                    if (list.isEmpty()) {
1394                        _poolMap.remove(key);
1395                        _poolList.remove(key);
1396                    }
1397                    _totalIdle--;
1398                    _totalInternalProcessing++;
1399                    itemsToRemove--;
1400                }
1401    
1402            }
1403            destroy(toDestroy);
1404        }
1405    
1406        /**
1407         * Clears the specified pool, removing all pooled instances corresponding to the given <code>key</code>.
1408         *
1409         * @param key the key to clear
1410         */
1411        public void clear(Object key) {
1412            Map toDestroy = new HashMap();
1413    
1414            final ObjectQueue pool;
1415            synchronized (this) {
1416                pool = (ObjectQueue)(_poolMap.remove(key));
1417                if (pool == null) {
1418                    return;
1419                } else {
1420                    _poolList.remove(key);
1421                }
1422                // Copy objects to new list so pool.queue can be cleared inside
1423                // the sync
1424                List objects = new ArrayList();
1425                objects.addAll(pool.queue);
1426                toDestroy.put(key, objects);
1427                _totalIdle = _totalIdle - pool.queue.size();
1428                _totalInternalProcessing =
1429                    _totalInternalProcessing + pool.queue.size();
1430                pool.queue.clear();
1431            }
1432            destroy(toDestroy);
1433        }
1434    
1435        /**
1436         * Assuming Map<Object,Collection<ObjectTimestampPair>>, destroy all
1437         * ObjectTimestampPair.value
1438         * 
1439         * @param m Map containing keyed pools to clear
1440         */
1441        private void destroy(Map m) {
1442            for (Iterator keys = m.keySet().iterator(); keys.hasNext();) {
1443                Object key = keys.next();
1444                Collection c = (Collection) m.get(key);
1445                for (Iterator it = c.iterator(); it.hasNext();) {
1446                    try {
1447                        _factory.destroyObject(
1448                                key,((ObjectTimestampPair)(it.next())).value);
1449                    } catch(Exception e) {
1450                        // ignore error, keep destroying the rest
1451                    } finally {
1452                        synchronized(this) {
1453                            _totalInternalProcessing--;
1454                            allocate();
1455                        }
1456                    }
1457                }
1458    
1459            }
1460        }
1461    
1462        /**
1463         * Returns the total number of instances current borrowed from this pool but not yet returned.
1464         *
1465         * @return the total number of instances currently borrowed from this pool
1466         */
1467        public synchronized int getNumActive() {
1468            return _totalActive;
1469        }
1470    
1471        /**
1472         * Returns the total number of instances currently idle in this pool.
1473         *
1474         * @return the total number of instances currently idle in this pool
1475         */
1476        public synchronized int getNumIdle() {
1477            return _totalIdle;
1478        }
1479    
1480        /**
1481         * Returns the number of instances currently borrowed from but not yet returned
1482         * to the pool corresponding to the given <code>key</code>.
1483         *
1484         * @param key the key to query
1485         * @return the number of instances corresponding to the given <code>key</code> currently borrowed in this pool
1486         */
1487        public synchronized int getNumActive(Object key) {
1488            final ObjectQueue pool = (ObjectQueue)(_poolMap.get(key));
1489            return pool != null ? pool.activeCount : 0;
1490        }
1491    
1492        /**
1493         * Returns the number of instances corresponding to the given <code>key</code> currently idle in this pool.
1494         *
1495         * @param key the key to query
1496         * @return the number of instances corresponding to the given <code>key</code> currently idle in this pool
1497         */
1498        public synchronized int getNumIdle(Object key) {
1499            final ObjectQueue pool = (ObjectQueue)(_poolMap.get(key));
1500            return pool != null ? pool.queue.size() : 0;
1501        }
1502    
1503        /**
1504         * <p>Returns an object to a keyed pool.</p>
1505         * 
1506         * <p>For the pool to function correctly, the object instance <strong>must</strong> have been borrowed
1507         * from the pool (under the same key) and not yet returned. Repeated <code>returnObject</code> calls on
1508         * the same object/key pair (with no <code>borrowObject</code> calls in between) will result in multiple
1509         * references to the object in the idle instance pool.</p>
1510         * 
1511         * <p>If {@link #getMaxIdle() maxIdle} is set to a positive value and the number of idle instances under the given
1512         * key has reached this value, the returning instance is destroyed.</p>
1513         * 
1514         * <p>If {@link #getTestOnReturn() testOnReturn} == true, the returning instance is validated before being returned
1515         * to the idle instance pool under the given key.  In this case, if validation fails, the instance is destroyed.</p>
1516         * 
1517         * @param key pool key
1518         * @param obj instance to return to the keyed pool
1519         * @throws Exception
1520         */
1521        public void returnObject(Object key, Object obj) throws Exception {
1522            try {
1523                addObjectToPool(key, obj, true);
1524            } catch (Exception e) {
1525                if (_factory != null) {
1526                    try {
1527                        _factory.destroyObject(key, obj);
1528                    } catch (Exception e2) {
1529                        // swallowed
1530                    }
1531                    // TODO: Correctness here depends on control in addObjectToPool.
1532                    // These two methods should be refactored, removing the
1533                    // "behavior flag", decrementNumActive, from addObjectToPool.
1534                    ObjectQueue pool = (ObjectQueue) (_poolMap.get(key));
1535                    if (pool != null) {
1536                        synchronized(this) {
1537                            pool.decrementActiveCount();
1538                            allocate();
1539                        }
1540                    }
1541                }
1542            }
1543        }
1544    
1545        /**
1546         * <p>Adds an object to the keyed pool.</p>
1547         * 
1548         * <p>Validates the object if testOnReturn == true and passivates it before returning it to the pool.
1549         * if validation or passivation fails, or maxIdle is set and there is no room in the pool, the instance
1550         * is destroyed.</p>
1551         * 
1552         * <p>Calls {@link #allocate()} on successful completion</p>
1553         * 
1554         * @param key pool key
1555         * @param obj instance to add to the keyed pool
1556         * @param decrementNumActive whether or not to decrement the active count associated with the keyed pool
1557         * @throws Exception
1558         */
1559        private void addObjectToPool(Object key, Object obj,
1560                boolean decrementNumActive) throws Exception {
1561    
1562            // if we need to validate this object, do so
1563            boolean success = true; // whether or not this object passed validation
1564            if (_testOnReturn && !_factory.validateObject(key, obj)) {
1565                success = false;
1566            } else {
1567                _factory.passivateObject(key, obj);
1568            }
1569    
1570            boolean shouldDestroy = !success;
1571            ObjectQueue pool;
1572    
1573            // Add instance to pool if there is room and it has passed validation
1574            // (if testOnreturn is set)
1575            synchronized (this) {
1576                // grab the pool (list) of objects associated with the given key
1577                pool = (ObjectQueue) (_poolMap.get(key));
1578                // if it doesn't exist, create it
1579                if (null == pool) {
1580                    pool = new ObjectQueue();
1581                    _poolMap.put(key, pool);
1582                    _poolList.add(key);
1583                }
1584                if (isClosed()) {
1585                    shouldDestroy = true;
1586                } else {
1587                    // if there's no space in the pool, flag the object for destruction
1588                    // else if we passivated successfully, return it to the pool
1589                    if (_maxIdle >= 0 && (pool.queue.size() >= _maxIdle)) {
1590                        shouldDestroy = true;
1591                    } else if (success) {
1592                        // borrowObject always takes the first element from the queue,
1593                        // so for LIFO, push on top, FIFO add to end
1594                        if (_lifo) {
1595                            pool.queue.addFirst(new ObjectTimestampPair(obj));
1596                        } else {
1597                            pool.queue.addLast(new ObjectTimestampPair(obj));
1598                        }
1599                        _totalIdle++;
1600                        if (decrementNumActive) {
1601                            pool.decrementActiveCount();
1602                        }
1603                        allocate();
1604                    }
1605                }
1606            }
1607    
1608            // Destroy the instance if necessary
1609            if (shouldDestroy) {
1610                try {
1611                    _factory.destroyObject(key, obj);
1612                } catch(Exception e) {
1613                    // ignored?
1614                }
1615                // Decrement active count *after* destroy if applicable
1616                if (decrementNumActive) {
1617                    synchronized(this) {
1618                        pool.decrementActiveCount();
1619                        allocate();
1620                    }
1621                }
1622            }
1623        }
1624    
1625        /**
1626         * <p>Invalidates the object instance associated with the given key.  Decrements the active count
1627         * associated with the given keyed pool and destroys the instance.</p>
1628         * 
1629         * @param key pool key
1630         * @param obj instance to invalidate
1631         * @throws Exception if an exception occurs destroying the object
1632         */
1633        public void invalidateObject(Object key, Object obj) throws Exception {
1634            try {
1635                _factory.destroyObject(key, obj);
1636            } finally {
1637                synchronized (this) {
1638                    ObjectQueue pool = (ObjectQueue) (_poolMap.get(key));
1639                    if (null == pool) {
1640                        pool = new ObjectQueue();
1641                        _poolMap.put(key, pool);
1642                        _poolList.add(key);
1643                    }
1644                    pool.decrementActiveCount();
1645                    allocate(); // _totalActive has changed
1646                }
1647            }
1648        }
1649    
1650        /**
1651         * Create an object using the {@link KeyedPoolableObjectFactory#makeObject factory},
1652         * passivate it, and then place it in the idle object pool.
1653         * <code>addObject</code> is useful for "pre-loading" a pool with idle objects.
1654         *
1655         * @param key the key a new instance should be added to
1656         * @throws Exception when {@link KeyedPoolableObjectFactory#makeObject} fails.
1657         * @throws IllegalStateException when no {@link #setFactory factory} has been set or after {@link #close} has been
1658         * called on this pool.
1659         */
1660        public void addObject(Object key) throws Exception {
1661            assertOpen();
1662            if (_factory == null) {
1663                throw new IllegalStateException("Cannot add objects without a factory.");
1664            }
1665            Object obj = _factory.makeObject(key);
1666            try {
1667                assertOpen();
1668                addObjectToPool(key, obj, false);
1669            } catch (IllegalStateException ex) { // Pool closed
1670                try {
1671                    _factory.destroyObject(key, obj);
1672                } catch (Exception ex2) {
1673                    // swallow
1674                }
1675                throw ex;
1676            }
1677        }
1678    
1679        /**
1680         * Registers a key for pool control.
1681         *
1682         * If <code>populateImmediately</code> is <code>true</code> and
1683         * <code>minIdle > 0,</code> the pool under the given key will be
1684         * populated immediately with <code>minIdle</code> idle instances.
1685         *
1686         * @param key - The key to register for pool control.
1687         * @param populateImmediately - If this is <code>true</code>, the pool
1688         * will be populated immediately.
1689         * @since Pool 1.3
1690         */
1691        public synchronized void preparePool(Object key, boolean populateImmediately) {
1692            ObjectQueue pool = (ObjectQueue)(_poolMap.get(key));
1693            if (null == pool) {
1694                pool = new ObjectQueue();
1695                _poolMap.put(key,pool);
1696                _poolList.add(key);
1697            }
1698    
1699            if (populateImmediately) {
1700                try {
1701                    // Create the pooled objects
1702                    ensureMinIdle(key);
1703                }
1704                catch (Exception e) {
1705                    //Do nothing
1706                }
1707            }
1708        }
1709    
1710        /**
1711         * Closes the keyed object pool.  Once the pool is closed, {@link #borrowObject(Object)}
1712         * will fail with IllegalStateException, but {@link #returnObject(Object, Object)} and
1713         * {@link #invalidateObject(Object, Object)} will continue to work. This method does not
1714         * {@link #clear()} the pool. The method is idempotent - that is, it is OK to call it on a closed
1715         * pool. 
1716         * 
1717         * @throws Exception
1718         */
1719        public void close() throws Exception {
1720            super.close();
1721            synchronized (this) {
1722                clear();
1723                if (null != _evictionCursor) {
1724                    _evictionCursor.close();
1725                    _evictionCursor = null;
1726                }
1727                if (null != _evictionKeyCursor) {
1728                    _evictionKeyCursor.close();
1729                    _evictionKeyCursor = null;
1730                }
1731                startEvictor(-1L);
1732            }
1733        }
1734    
1735        /**
1736         * <p>Sets the keyed poolable object factory associated with this pool.</p>
1737         * 
1738         * <p>If this method is called when objects are checked out of any of the keyed pools,
1739         * an IllegalStateException is thrown.  Calling this method also has the side effect of
1740         * destroying any idle instances in existing keyed pools.</p>
1741         * 
1742         * @param factory KeyedPoolableObjectFactory to use when creating keyed object pool instances
1743         * @throws IllegalStateException if there are active (checked out) instances associated with this keyed object pool
1744         */
1745        public void setFactory(KeyedPoolableObjectFactory factory) throws IllegalStateException {
1746            Map toDestroy = new HashMap();
1747            synchronized (this) {
1748                assertOpen();
1749                if (0 < getNumActive()) {
1750                    throw new IllegalStateException("Objects are already active");
1751                } else {
1752                    for (Iterator it = _poolMap.keySet().iterator(); it.hasNext();) {
1753                        Object key = it.next();
1754                        ObjectQueue pool = (ObjectQueue)_poolMap.get(key);
1755                        if (pool != null) {
1756                            // Copy objects to new list so pool.queue can be cleared
1757                            // inside the sync
1758                            List objects = new ArrayList();
1759                            objects.addAll(pool.queue);
1760                            toDestroy.put(key, objects);
1761                            it.remove();
1762                            _poolList.remove(key);
1763                            _totalIdle = _totalIdle - pool.queue.size();
1764                            _totalInternalProcessing =
1765                                _totalInternalProcessing + pool.queue.size();
1766                            pool.queue.clear();
1767                        }
1768                    }
1769                    _factory = factory;
1770                }
1771            }
1772            destroy(toDestroy);
1773        }
1774    
1775        /**
1776         * <p>Perform <code>numTests</code> idle object eviction tests, evicting
1777         * examined objects that meet the criteria for eviction. If
1778         * <code>testWhileIdle</code> is true, examined objects are validated
1779         * when visited (and removed if invalid); otherwise only objects that
1780         * have been idle for more than <code>minEvicableIdletimeMillis</code>
1781         * are removed.</p>
1782         *
1783         * <p>Successive activations of this method examine objects in keyed pools
1784         * in sequence, cycling through the keys and examining objects in
1785         * oldest-to-youngest order within the keyed pools.</p>
1786         *
1787         * @throws Exception when there is a problem evicting idle objects.
1788         */
1789        public void evict() throws Exception {
1790            Object key = null;
1791            boolean testWhileIdle;
1792            long minEvictableIdleTimeMillis;
1793    
1794            synchronized (this) {
1795                // Get local copy of current config. Can't sync when used later as
1796                // it can result in a deadlock. Has the added advantage that config
1797                // is consistent for entire method execution
1798                testWhileIdle = _testWhileIdle;
1799                minEvictableIdleTimeMillis = _minEvictableIdleTimeMillis;
1800    
1801                // Initialize key to last key value
1802                if (_evictionKeyCursor != null &&
1803                        _evictionKeyCursor._lastReturned != null) {
1804                    key = _evictionKeyCursor._lastReturned.value();
1805                }
1806            }
1807    
1808            for (int i=0, m=getNumTests(); i<m; i++) {
1809                final ObjectTimestampPair pair;
1810                synchronized (this) {
1811                    // make sure pool map is not empty; otherwise do nothing
1812                    if (_poolMap == null || _poolMap.size() == 0) {
1813                        continue;
1814                    }
1815    
1816                    // if we don't have a key cursor, then create one
1817                    if (null == _evictionKeyCursor) {
1818                        resetEvictionKeyCursor();
1819                        key = null;
1820                    }
1821    
1822                    // if we don't have an object cursor, create one
1823                    if (null == _evictionCursor) {
1824                        // if the _evictionKeyCursor has a next value, use this key
1825                        if (_evictionKeyCursor.hasNext()) {
1826                            key = _evictionKeyCursor.next();
1827                            resetEvictionObjectCursor(key);
1828                        } else {
1829                            // Reset the key cursor and try again
1830                            resetEvictionKeyCursor();
1831                            if (_evictionKeyCursor != null) {
1832                                if (_evictionKeyCursor.hasNext()) {
1833                                    key = _evictionKeyCursor.next();
1834                                    resetEvictionObjectCursor(key);
1835                                }
1836                            }
1837                        }
1838                    }
1839    
1840                    if (_evictionCursor == null) {
1841                        continue; // should never happen; do nothing
1842                    }
1843    
1844                    // If eviction cursor is exhausted, try to move
1845                    // to the next key and reset
1846                    if ((_lifo && !_evictionCursor.hasPrevious()) ||
1847                            (!_lifo && !_evictionCursor.hasNext())) {
1848                        if (_evictionKeyCursor != null) {
1849                            if (_evictionKeyCursor.hasNext()) {
1850                                key = _evictionKeyCursor.next();
1851                                resetEvictionObjectCursor(key);
1852                            } else { // Need to reset Key cursor
1853                                resetEvictionKeyCursor();
1854                                if (_evictionKeyCursor != null) {
1855                                    if (_evictionKeyCursor.hasNext()) {
1856                                        key = _evictionKeyCursor.next();
1857                                        resetEvictionObjectCursor(key);
1858                                    }
1859                                }
1860                            }
1861                        }
1862                    }
1863    
1864                    if ((_lifo && !_evictionCursor.hasPrevious()) ||
1865                            (!_lifo && !_evictionCursor.hasNext())) {
1866                        continue; // reset failed, do nothing
1867                    }
1868    
1869                    // if LIFO and the _evictionCursor has a previous object,
1870                    // or FIFO and _evictionCursor has a next object, test it
1871                    pair = _lifo ?
1872                            (ObjectTimestampPair) _evictionCursor.previous() :
1873                            (ObjectTimestampPair) _evictionCursor.next();
1874                    _evictionCursor.remove();
1875                    _totalIdle--;
1876                    _totalInternalProcessing++;
1877                }
1878    
1879                boolean removeObject=false;
1880                if ((minEvictableIdleTimeMillis > 0) &&
1881                   (System.currentTimeMillis() - pair.tstamp >
1882                   minEvictableIdleTimeMillis)) {
1883                    removeObject=true;
1884                }
1885                if (testWhileIdle && removeObject == false) {
1886                    boolean active = false;
1887                    try {
1888                        _factory.activateObject(key,pair.value);
1889                        active = true;
1890                    } catch(Exception e) {
1891                        removeObject=true;
1892                    }
1893                    if (active) {
1894                        if (!_factory.validateObject(key,pair.value)) {
1895                            removeObject=true;
1896                        } else {
1897                            try {
1898                                _factory.passivateObject(key,pair.value);
1899                            } catch(Exception e) {
1900                                removeObject=true;
1901                            }
1902                        }
1903                    }
1904                }
1905    
1906                if (removeObject) {
1907                    try {
1908                        _factory.destroyObject(key, pair.value);
1909                    } catch(Exception e) {
1910                        // ignored
1911                    } finally {
1912                        // Do not remove the key from the _poolList or _poolmap,
1913                        // even if the list stored in the _poolMap for this key is
1914                        // empty when minIdle > 0.
1915                        //
1916                        // Otherwise if it was the last object for that key,
1917                        // drop that pool
1918                        if (_minIdle == 0) {
1919                            synchronized (this) {
1920                                ObjectQueue objectQueue =
1921                                    (ObjectQueue)_poolMap.get(key);
1922                                if (objectQueue != null &&
1923                                        objectQueue.queue.isEmpty()) {
1924                                    _poolMap.remove(key);
1925                                    _poolList.remove(key);
1926                                }
1927                            }
1928                        }
1929                    }
1930                }
1931                synchronized (this) {
1932                    if (!removeObject) {
1933                        _evictionCursor.add(pair);
1934                        _totalIdle++;
1935                        if (_lifo) {
1936                            // Skip over the element we just added back
1937                            _evictionCursor.previous();
1938                        }
1939                    }
1940                    _totalInternalProcessing--;
1941                }
1942            }
1943        }
1944    
1945        /**
1946         * Resets the eviction key cursor and closes any
1947         * associated eviction object cursor
1948         */
1949        private void resetEvictionKeyCursor() {
1950            if (_evictionKeyCursor != null) {
1951                _evictionKeyCursor.close();
1952            }
1953            _evictionKeyCursor = _poolList.cursor();
1954            if (null != _evictionCursor) {
1955                _evictionCursor.close();
1956                _evictionCursor = null;
1957            }
1958        }
1959    
1960        /**
1961         * Resets the eviction object cursor for the given key
1962         *
1963         * @param key eviction key
1964         */
1965        private void resetEvictionObjectCursor(Object key) {
1966            if (_evictionCursor != null) {
1967                _evictionCursor.close();
1968            }
1969            if (_poolMap == null) {
1970                return;
1971            }
1972            ObjectQueue pool = (ObjectQueue) (_poolMap.get(key));
1973            if (pool != null) {
1974                CursorableLinkedList queue = pool.queue;
1975                _evictionCursor = queue.cursor(_lifo ? queue.size() : 0);
1976            }
1977        }
1978    
1979        /**
1980         * Iterates through all the known keys and creates any necessary objects to maintain
1981         * the minimum level of pooled objects.
1982         * @see #getMinIdle
1983         * @see #setMinIdle
1984         * @throws Exception If there was an error whilst creating the pooled objects.
1985         */
1986        private void ensureMinIdle() throws Exception {
1987            //Check if should sustain the pool
1988            if (_minIdle > 0) {
1989                Object[] keysCopy;
1990                synchronized(this) {
1991                    // Get the current set of keys
1992                    keysCopy = _poolMap.keySet().toArray();
1993                }
1994    
1995                // Loop through all elements in _poolList
1996                // Find out the total number of max active and max idle for that class
1997                // If the number is less than the minIdle, do creation loop to boost numbers
1998                for (int i=0; i < keysCopy.length; i++) {
1999                    //Get the next key to process
2000                    ensureMinIdle(keysCopy[i]);
2001                }
2002            }
2003        }
2004    
2005        /**
2006         * Re-creates any needed objects to maintain the minimum levels of
2007         * pooled objects for the specified key.
2008         *
2009         * This method uses {@link #calculateDefecit} to calculate the number
2010         * of objects to be created. {@link #calculateDefecit} can be overridden to
2011         * provide a different method of calculating the number of objects to be
2012         * created.
2013         * @param key The key to process
2014         * @throws Exception If there was an error whilst creating the pooled objects
2015         */
2016        private void ensureMinIdle(Object key) throws Exception {
2017            // Calculate current pool objects
2018            ObjectQueue pool;
2019            synchronized(this) {
2020                pool = (ObjectQueue)(_poolMap.get(key));
2021            }
2022            if (pool == null) {
2023                return;
2024            }
2025    
2026            // this method isn't synchronized so the
2027            // calculateDeficit is done at the beginning
2028            // as a loop limit and a second time inside the loop
2029            // to stop when another thread already returned the
2030            // needed objects
2031            int objectDeficit = calculateDefecit(pool, false);
2032    
2033            for (int i = 0; i < objectDeficit && calculateDefecit(pool, true) > 0; i++) {
2034                try {
2035                    addObject(key);
2036                } finally {
2037                    synchronized (this) {
2038                        pool.decrementInternalProcessingCount();
2039                        allocate();
2040                    }
2041                }
2042            }
2043        }
2044    
2045        //--- non-public methods ----------------------------------------
2046    
2047        /**
2048         * Start the eviction thread or service, or when
2049         * <code>delay</code> is non-positive, stop it
2050         * if it is already running.
2051         *
2052         * @param delay milliseconds between evictor runs.
2053         */
2054        protected synchronized void startEvictor(long delay) {
2055            if (null != _evictor) {
2056                EvictionTimer.cancel(_evictor);
2057                _evictor = null;
2058            }
2059            if (delay > 0) {
2060                _evictor = new Evictor();
2061                EvictionTimer.schedule(_evictor, delay, delay);
2062            }
2063        }
2064    
2065        /**
2066         * Returns pool info including {@link #getNumActive()}, {@link #getNumIdle()}
2067         * and currently defined keys.
2068         * 
2069         * @return string containing debug information
2070         */
2071        synchronized String debugInfo() {
2072            StringBuffer buf = new StringBuffer();
2073            buf.append("Active: ").append(getNumActive()).append("\n");
2074            buf.append("Idle: ").append(getNumIdle()).append("\n");
2075            Iterator it = _poolMap.keySet().iterator();
2076            while (it.hasNext()) {
2077                Object key = it.next();
2078                buf.append("\t").append(key).append(" ").append(_poolMap.get(key)).append("\n");
2079            }
2080            return buf.toString();
2081        }
2082    
2083        /** 
2084         * Returns the number of tests to be performed in an Evictor run,
2085         * based on the current values of <code>_numTestsPerEvictionRun</code>
2086         * and <code>_totalIdle</code>.
2087         * 
2088         * @see #setNumTestsPerEvictionRun
2089         * @return the number of tests for the Evictor to run
2090         */
2091        private synchronized int getNumTests() {
2092            if (_numTestsPerEvictionRun >= 0) {
2093                return Math.min(_numTestsPerEvictionRun, _totalIdle);
2094            } else {
2095                return(int)(Math.ceil(_totalIdle/Math.abs((double)_numTestsPerEvictionRun)));
2096            }
2097        }
2098    
2099        /**
2100         * This returns the number of objects to create during the pool
2101         * sustain cycle. This will ensure that the minimum number of idle
2102         * instances is maintained without going past the maxActive value.
2103         * 
2104         * @param pool the ObjectPool to calculate the deficit for
2105         * @param incrementInternal - Should the count of objects currently under
2106         *                            some form of internal processing be
2107         *                            incremented?
2108         * @return The number of objects to be created
2109         */
2110        private synchronized int calculateDefecit(ObjectQueue pool,
2111                boolean incrementInternal) {
2112            int objectDefecit = 0;
2113    
2114            //Calculate no of objects needed to be created, in order to have
2115            //the number of pooled objects < maxActive();
2116            objectDefecit = getMinIdle() - pool.queue.size();
2117            if (getMaxActive() > 0) {
2118                int growLimit = Math.max(0, getMaxActive() - pool.activeCount - pool.queue.size() - pool.internalProcessingCount);
2119                objectDefecit = Math.min(objectDefecit, growLimit);
2120            }
2121    
2122            // Take the maxTotal limit into account
2123            if (getMaxTotal() > 0) {
2124                int growLimit = Math.max(0, getMaxTotal() - getNumActive() - getNumIdle() - _totalInternalProcessing);
2125                objectDefecit = Math.min(objectDefecit, growLimit);
2126            }
2127    
2128            if (incrementInternal && objectDefecit > 0) {
2129                pool.incrementInternalProcessingCount();
2130            }
2131            return objectDefecit;
2132        }
2133    
2134        //--- inner classes ----------------------------------------------
2135    
2136        /**
2137         * A "struct" that keeps additional information about the actual queue of pooled objects.
2138         */
2139        private class ObjectQueue {
2140            /** Number of instances checked out to clients from this queue */
2141            private int activeCount = 0;
2142            
2143            /** Idle instance queue */
2144            private final CursorableLinkedList queue = new CursorableLinkedList();
2145            
2146            /** Number of instances in process of being created */
2147            private int internalProcessingCount = 0;
2148    
2149            /** Increment the active count for this queue */
2150            void incrementActiveCount() {
2151                synchronized (GenericKeyedObjectPool.this) {
2152                    _totalActive++;
2153                }
2154                activeCount++;
2155            }
2156    
2157            /** Decrement the active count for this queue */
2158            void decrementActiveCount() {
2159                synchronized (GenericKeyedObjectPool.this) {
2160                    _totalActive--;
2161                }
2162                if (activeCount > 0) {
2163                    activeCount--;
2164                }
2165            }
2166    
2167            /** Record the fact that one more instance is queued for creation */
2168            void incrementInternalProcessingCount() {
2169                synchronized (GenericKeyedObjectPool.this) {
2170                    _totalInternalProcessing++;
2171                }
2172                internalProcessingCount++;
2173            }
2174    
2175            /** Decrement the number of instances in process of being created */
2176            void decrementInternalProcessingCount() {
2177                synchronized (GenericKeyedObjectPool.this) {
2178                    _totalInternalProcessing--;
2179                }
2180                internalProcessingCount--;
2181            }
2182        }
2183    
2184        /**
2185         * A simple "struct" encapsulating an object instance and a timestamp.
2186         *
2187         * Implements Comparable, objects are sorted from old to new.
2188         *
2189         * This is also used by {@link GenericObjectPool}.
2190         */
2191        static class ObjectTimestampPair implements Comparable {
2192            
2193            /** Object instance */
2194            Object value;
2195            
2196            /** timestamp */
2197            long tstamp;
2198    
2199            /**
2200             * Create a new ObjectTimestampPair using the given object and the current system time.
2201             * @param val object instance
2202             */
2203            ObjectTimestampPair(Object val) {
2204                this(val, System.currentTimeMillis());
2205            }
2206    
2207            /**
2208             * Create a new ObjectTimeStampPair using the given object and timestamp value.
2209             * @param val object instance
2210             * @param time long representation of timestamp
2211             */
2212            ObjectTimestampPair(Object val, long time) {
2213                value = val;
2214                tstamp = time;
2215            }
2216    
2217            /**
2218             * Returns a string representation.
2219             * 
2220             * @return String representing this ObjectTimestampPair
2221             */
2222            public String toString() {
2223                return value + ";" + tstamp;
2224            }
2225    
2226            /**
2227             * Compares this to another object by casting the argument to an
2228             * ObjectTimestampPair.
2229             * 
2230             * @param obj object to cmpare
2231             * @return result of comparison
2232             */
2233            public int compareTo(Object obj) {
2234                return compareTo((ObjectTimestampPair) obj);
2235            }
2236    
2237            /**
2238             * Compares this to another ObjectTimestampPair, using the timestamp as basis for comparison.
2239             * Implementation is consistent with equals.
2240             * 
2241             * @param other object to compare
2242             * @return result of comparison
2243             */
2244            public int compareTo(ObjectTimestampPair other) {
2245                final long tstampdiff = this.tstamp - other.tstamp;
2246                if (tstampdiff == 0) {
2247                    // make sure the natural ordering is consistent with equals
2248                    // see java.lang.Comparable Javadocs
2249                    return System.identityHashCode(this) - System.identityHashCode(other);
2250                } else {
2251                    // handle int overflow
2252                    return (int)Math.min(Math.max(tstampdiff, Integer.MIN_VALUE), Integer.MAX_VALUE);
2253                }
2254            }
2255        }
2256    
2257        /**
2258         * The idle object evictor {@link TimerTask}.
2259         * @see GenericKeyedObjectPool#setTimeBetweenEvictionRunsMillis
2260         */
2261        private class Evictor extends TimerTask {
2262            /**
2263             * Run pool maintenance.  Evict objects qualifying for eviction and then
2264             * invoke {@link GenericKeyedObjectPool#ensureMinIdle()}.
2265             */
2266            public void run() {
2267                //Evict from the pool
2268                try {
2269                    evict();
2270                } catch(Exception e) {
2271                    // ignored
2272                } catch(OutOfMemoryError oome) {
2273                    // Log problem but give evictor thread a chance to continue in
2274                    // case error is recoverable
2275                    oome.printStackTrace(System.err);
2276                }
2277                //Re-create idle instances.
2278                try {
2279                    ensureMinIdle();
2280                } catch (Exception e) {
2281                    // ignored
2282                }
2283            }
2284        }
2285    
2286        /**
2287         * A simple "struct" encapsulating the
2288         * configuration information for a <code>GenericKeyedObjectPool</code>.
2289         * @see GenericKeyedObjectPool#GenericKeyedObjectPool(KeyedPoolableObjectFactory,GenericKeyedObjectPool.Config)
2290         * @see GenericKeyedObjectPool#setConfig
2291         */
2292        public static class Config {
2293            /**
2294             * @see GenericKeyedObjectPool#setMaxIdle
2295             */
2296            public int maxIdle = GenericKeyedObjectPool.DEFAULT_MAX_IDLE;
2297            /**
2298             * @see GenericKeyedObjectPool#setMaxActive
2299             */
2300            public int maxActive = GenericKeyedObjectPool.DEFAULT_MAX_ACTIVE;
2301            /**
2302             * @see GenericKeyedObjectPool#setMaxTotal
2303             */
2304            public int maxTotal = GenericKeyedObjectPool.DEFAULT_MAX_TOTAL;
2305            /**
2306             * @see GenericKeyedObjectPool#setMinIdle
2307             */
2308            public int minIdle = GenericKeyedObjectPool.DEFAULT_MIN_IDLE;
2309            /**
2310             * @see GenericKeyedObjectPool#setMaxWait
2311             */
2312            public long maxWait = GenericKeyedObjectPool.DEFAULT_MAX_WAIT;
2313            /**
2314             * @see GenericKeyedObjectPool#setWhenExhaustedAction
2315             */
2316            public byte whenExhaustedAction = GenericKeyedObjectPool.DEFAULT_WHEN_EXHAUSTED_ACTION;
2317            /**
2318             * @see GenericKeyedObjectPool#setTestOnBorrow
2319             */
2320            public boolean testOnBorrow = GenericKeyedObjectPool.DEFAULT_TEST_ON_BORROW;
2321            /**
2322             * @see GenericKeyedObjectPool#setTestOnReturn
2323             */
2324            public boolean testOnReturn = GenericKeyedObjectPool.DEFAULT_TEST_ON_RETURN;
2325            /**
2326             * @see GenericKeyedObjectPool#setTestWhileIdle
2327             */
2328            public boolean testWhileIdle = GenericKeyedObjectPool.DEFAULT_TEST_WHILE_IDLE;
2329            /**
2330             * @see GenericKeyedObjectPool#setTimeBetweenEvictionRunsMillis
2331             */
2332            public long timeBetweenEvictionRunsMillis = GenericKeyedObjectPool.DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;
2333            /**
2334             * @see GenericKeyedObjectPool#setNumTestsPerEvictionRun
2335             */
2336            public int numTestsPerEvictionRun =  GenericKeyedObjectPool.DEFAULT_NUM_TESTS_PER_EVICTION_RUN;
2337            /**
2338             * @see GenericKeyedObjectPool#setMinEvictableIdleTimeMillis
2339             */
2340            public long minEvictableIdleTimeMillis = GenericKeyedObjectPool.DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;
2341            /**
2342             * @see GenericKeyedObjectPool#setLifo
2343             */
2344            public boolean lifo = GenericKeyedObjectPool.DEFAULT_LIFO;
2345        }
2346    
2347        /**
2348         * Latch used to control allocation order of objects to threads to ensure
2349         * fairness. That is, for each key, objects are allocated to threads in the order
2350         * that threads request objects.
2351         * 
2352         * @since 1.5
2353         */
2354        private static final class Latch {
2355            
2356            /** key of associated pool */
2357            private final Object _key;
2358            
2359            /** keyed pool associated with this latch */
2360            private ObjectQueue _pool;
2361            
2362            /** holds an ObjectTimestampPair when this latch has been allocated an instance */
2363            private ObjectTimestampPair _pair;
2364            
2365            /** indicates that this latch can create an instance */
2366            private boolean _mayCreate = false;
2367    
2368            /**
2369             * Create a latch with the given key
2370             * @param key key of the pool associated with this latch
2371             */
2372            private Latch(Object key) {
2373                _key = key;
2374            }
2375    
2376            /**
2377             * Retuns the key of the associated pool
2378             * @return associated pool key
2379             */
2380            private synchronized Object getkey() {
2381                return _key;
2382            }
2383    
2384            /**
2385             * Returns the pool associated with this latch
2386             * @return pool
2387             */
2388            private synchronized ObjectQueue getPool() {
2389                return _pool;
2390            }
2391            
2392            /**
2393             * Sets the pool associated with this latch
2394             * @param pool the pool
2395             */
2396            private synchronized void setPool(ObjectQueue pool) {
2397                _pool = pool;
2398            }
2399    
2400            /**
2401             * Gets the ObjectTimestampPair allocated to this latch.
2402             * Returns null if this latch does not have an instance allocated to it. 
2403             * @return the associated ObjectTimestampPair
2404             */
2405            private synchronized ObjectTimestampPair getPair() {
2406                return _pair;
2407            }
2408            
2409            /**
2410             * Allocate an ObjectTimestampPair to this latch.
2411             * @param pair ObjectTimestampPair on this latch
2412             */
2413            private synchronized void setPair(ObjectTimestampPair pair) {
2414                _pair = pair;
2415            }
2416    
2417            /**
2418             * Whether or not this latch can create an instance
2419             * @return true if this latch has an instance creation permit
2420             */
2421            private synchronized boolean mayCreate() {
2422                return _mayCreate;
2423            }
2424            
2425            /**
2426             * Sets the mayCreate property
2427             * 
2428             * @param mayCreate true means this latch can create an instance
2429             */
2430            private synchronized void setMayCreate(boolean mayCreate) {
2431                _mayCreate = mayCreate;
2432            }
2433    
2434            /**
2435             * Reset the latch data. Used when an allocation fails and the latch
2436             * needs to be re-added to the queue.
2437             */
2438            private synchronized void reset() {
2439                _pair = null;
2440                _mayCreate = false;
2441            }
2442        }
2443    
2444        //--- protected attributes ---------------------------------------
2445    
2446        /**
2447         * The cap on the number of idle instances in the pool.
2448         * @see #setMaxIdle
2449         * @see #getMaxIdle
2450         */
2451        private int _maxIdle = DEFAULT_MAX_IDLE;
2452    
2453        /**
2454         * The minimum no of idle objects to keep in the pool.
2455         * @see #setMinIdle
2456         * @see #getMinIdle
2457         */
2458        private int _minIdle = DEFAULT_MIN_IDLE;
2459    
2460        /**
2461         * The cap on the number of active instances from the pool.
2462         * @see #setMaxActive
2463         * @see #getMaxActive
2464         */
2465        private int _maxActive = DEFAULT_MAX_ACTIVE;
2466    
2467        /**
2468         * The cap on the total number of instances from the pool if non-positive.
2469         * @see #setMaxTotal
2470         * @see #getMaxTotal
2471         */
2472        private int _maxTotal = DEFAULT_MAX_TOTAL;
2473    
2474        /**
2475         * The maximum amount of time (in millis) the
2476         * {@link #borrowObject} method should block before throwing
2477         * an exception when the pool is exhausted and the
2478         * {@link #getWhenExhaustedAction "when exhausted" action} is
2479         * {@link #WHEN_EXHAUSTED_BLOCK}.
2480         *
2481         * When less than or equal to 0, the {@link #borrowObject} method
2482         * may block indefinitely.
2483         *
2484         * @see #setMaxWait
2485         * @see #getMaxWait
2486         * @see #WHEN_EXHAUSTED_BLOCK
2487         * @see #setWhenExhaustedAction
2488         * @see #getWhenExhaustedAction
2489         */
2490        private long _maxWait = DEFAULT_MAX_WAIT;
2491    
2492        /**
2493         * The action to take when the {@link #borrowObject} method
2494         * is invoked when the pool is exhausted (the maximum number
2495         * of "active" objects has been reached).
2496         *
2497         * @see #WHEN_EXHAUSTED_BLOCK
2498         * @see #WHEN_EXHAUSTED_FAIL
2499         * @see #WHEN_EXHAUSTED_GROW
2500         * @see #DEFAULT_WHEN_EXHAUSTED_ACTION
2501         * @see #setWhenExhaustedAction
2502         * @see #getWhenExhaustedAction
2503         */
2504        private byte _whenExhaustedAction = DEFAULT_WHEN_EXHAUSTED_ACTION;
2505    
2506        /**
2507         * When <code>true</code>, objects will be
2508         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
2509         * before being returned by the {@link #borrowObject}
2510         * method.  If the object fails to validate,
2511         * it will be dropped from the pool, and we will attempt
2512         * to borrow another.
2513         *
2514         * @see #setTestOnBorrow
2515         * @see #getTestOnBorrow
2516         */
2517        private volatile boolean _testOnBorrow = DEFAULT_TEST_ON_BORROW;
2518    
2519        /**
2520         * When <code>true</code>, objects will be
2521         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
2522         * before being returned to the pool within the
2523         * {@link #returnObject}.
2524         *
2525         * @see #getTestOnReturn
2526         * @see #setTestOnReturn
2527         */
2528        private volatile boolean _testOnReturn = DEFAULT_TEST_ON_RETURN;
2529    
2530        /**
2531         * When <code>true</code>, objects will be
2532         * {@link org.apache.commons.pool.PoolableObjectFactory#validateObject validated}
2533         * by the idle object evictor (if any).  If an object
2534         * fails to validate, it will be dropped from the pool.
2535         *
2536         * @see #setTestWhileIdle
2537         * @see #getTestWhileIdle
2538         * @see #getTimeBetweenEvictionRunsMillis
2539         * @see #setTimeBetweenEvictionRunsMillis
2540         */
2541        private boolean _testWhileIdle = DEFAULT_TEST_WHILE_IDLE;
2542    
2543        /**
2544         * The number of milliseconds to sleep between runs of the
2545         * idle object evictor thread.
2546         * When non-positive, no idle object evictor thread will be
2547         * run.
2548         *
2549         * @see #setTimeBetweenEvictionRunsMillis
2550         * @see #getTimeBetweenEvictionRunsMillis
2551         */
2552        private long _timeBetweenEvictionRunsMillis = DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;
2553    
2554        /**
2555         * The number of objects to examine during each run of the
2556         * idle object evictor thread (if any).
2557         * <p>
2558         * When a negative value is supplied, <code>ceil({@link #getNumIdle})/abs({@link #getNumTestsPerEvictionRun})</code>
2559         * tests will be run.  I.e., when the value is <code>-n</code>, roughly one <code>n</code>th of the
2560         * idle objects will be tested per run.
2561         *
2562         * @see #setNumTestsPerEvictionRun
2563         * @see #getNumTestsPerEvictionRun
2564         * @see #getTimeBetweenEvictionRunsMillis
2565         * @see #setTimeBetweenEvictionRunsMillis
2566         */
2567        private int _numTestsPerEvictionRun =  DEFAULT_NUM_TESTS_PER_EVICTION_RUN;
2568    
2569        /**
2570         * The minimum amount of time an object may sit idle in the pool
2571         * before it is eligible for eviction by the idle object evictor
2572         * (if any).
2573         * When non-positive, no objects will be evicted from the pool
2574         * due to idle time alone.
2575         *
2576         * @see #setMinEvictableIdleTimeMillis
2577         * @see #getMinEvictableIdleTimeMillis
2578         * @see #getTimeBetweenEvictionRunsMillis
2579         * @see #setTimeBetweenEvictionRunsMillis
2580         */
2581        private long _minEvictableIdleTimeMillis = DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;
2582    
2583        /** My hash of pools (ObjectQueue). */
2584        private Map _poolMap = null;
2585    
2586        /** The total number of active instances. */
2587        private int _totalActive = 0;
2588    
2589        /** The total number of idle instances. */
2590        private int _totalIdle = 0;
2591    
2592        /**
2593         * The number of objects subject to some form of internal processing
2594         * (usually creation or destruction) that should be included in the total
2595         * number of objects but are neither active nor idle.
2596         */
2597        private int _totalInternalProcessing = 0;
2598    
2599        /** My {@link KeyedPoolableObjectFactory}. */
2600        private KeyedPoolableObjectFactory _factory = null;
2601    
2602        /**
2603         * My idle object eviction {@link TimerTask}, if any.
2604         */
2605        private Evictor _evictor = null;
2606    
2607        /**
2608         * A cursorable list of my pools.
2609         * @see GenericKeyedObjectPool.Evictor#run
2610         */
2611        private CursorableLinkedList _poolList = null;
2612    
2613        /** Eviction cursor (over instances within-key) */
2614        private CursorableLinkedList.Cursor _evictionCursor = null;
2615        
2616        /** Eviction cursor (over keys) */
2617        private CursorableLinkedList.Cursor _evictionKeyCursor = null;
2618    
2619        /** Whether or not the pools behave as LIFO queues (last in first out) */
2620        private boolean _lifo = DEFAULT_LIFO;
2621    
2622        /**
2623         * Used to track the order in which threads call {@link #borrowObject()} so
2624         * that objects can be allocated in the order in which the threads requested
2625         * them.
2626         */
2627        private LinkedList _allocationQueue = new LinkedList();
2628    
2629    }