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org.apache.commons.pool
Class PoolUtils

java.lang.Object
  extended by org.apache.commons.pool.PoolUtils

public final class PoolUtils
extends Object

This class consists exclusively of static methods that operate on or return ObjectPool or KeyedObjectPool related interfaces.

Since:
Pool 1.3
Version:
$Revision: 777748 $ $Date: 2009-05-22 20:00:44 -0400 (Fri, 22 May 2009) $
Author:
Sandy McArthur

Constructor Summary
PoolUtils()
          PoolUtils instances should NOT be constructed in standard programming.
 
Method Summary
static ObjectPool adapt(KeyedObjectPool keyedPool)
          Adapt a KeyedObjectPool instance to work where an ObjectPool is needed.
static ObjectPool adapt(KeyedObjectPool keyedPool, Object key)
          Adapt a KeyedObjectPool instance to work where an ObjectPool is needed using the specified key when delegating.
static PoolableObjectFactory adapt(KeyedPoolableObjectFactory keyedFactory)
          Adapt a KeyedPoolableObjectFactory instance to work where a PoolableObjectFactory is needed.
static PoolableObjectFactory adapt(KeyedPoolableObjectFactory keyedFactory, Object key)
          Adapt a KeyedPoolableObjectFactory instance to work where a PoolableObjectFactory is needed using the specified key when delegating.
static KeyedObjectPool adapt(ObjectPool pool)
          Adapt an ObjectPool to work where an KeyedObjectPool is needed.
static KeyedPoolableObjectFactory adapt(PoolableObjectFactory factory)
          Adapt a PoolableObjectFactory instance to work where a KeyedPoolableObjectFactory is needed.
static KeyedObjectPool checkedPool(KeyedObjectPool keyedPool, Class type)
          Wraps a KeyedObjectPool and dynamically checks the type of objects borrowed and returned to the keyedPool.
static ObjectPool checkedPool(ObjectPool pool, Class type)
          Wraps an ObjectPool and dynamically checks the type of objects borrowed and returned to the pool.
static Map checkMinIdle(KeyedObjectPool keyedPool, Collection keys, int minIdle, long period)
          Periodically check the idle object count for each key in the Collection keys in the keyedPool.
static TimerTask checkMinIdle(KeyedObjectPool keyedPool, Object key, int minIdle, long period)
          Periodically check the idle object count for the key in the keyedPool.
static TimerTask checkMinIdle(ObjectPool pool, int minIdle, long period)
          Periodically check the idle object count for the pool.
static KeyedObjectPool erodingPool(KeyedObjectPool keyedPool)
          Returns a pool that adaptively decreases it's size when idle objects are no longer needed.
static KeyedObjectPool erodingPool(KeyedObjectPool keyedPool, float factor)
          Returns a pool that adaptively decreases it's size when idle objects are no longer needed.
static KeyedObjectPool erodingPool(KeyedObjectPool keyedPool, float factor, boolean perKey)
          Returns a pool that adaptively decreases it's size when idle objects are no longer needed.
static ObjectPool erodingPool(ObjectPool pool)
          Returns a pool that adaptively decreases it's size when idle objects are no longer needed.
static ObjectPool erodingPool(ObjectPool pool, float factor)
          Returns a pool that adaptively decreases it's size when idle objects are no longer needed.
static void prefill(KeyedObjectPool keyedPool, Collection keys, int count)
          Call addObject(Object) on keyedPool with each key in keys for count number of times.
static void prefill(KeyedObjectPool keyedPool, Object key, int count)
          Call addObject(Object) on keyedPool with key count number of times.
static void prefill(ObjectPool pool, int count)
          Call addObject() on pool count number of times.
static KeyedObjectPool synchronizedPool(KeyedObjectPool keyedPool)
          Returns a synchronized (thread-safe) KeyedObjectPool backed by the specified KeyedObjectPool.
static ObjectPool synchronizedPool(ObjectPool pool)
          Returns a synchronized (thread-safe) ObjectPool backed by the specified ObjectPool.
static KeyedPoolableObjectFactory synchronizedPoolableFactory(KeyedPoolableObjectFactory keyedFactory)
          Returns a synchronized (thread-safe) KeyedPoolableObjectFactory backed by the specified KeyedPoolableObjectFactory.
static PoolableObjectFactory synchronizedPoolableFactory(PoolableObjectFactory factory)
          Returns a synchronized (thread-safe) PoolableObjectFactory backed by the specified PoolableObjectFactory.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PoolUtils

public PoolUtils()
PoolUtils instances should NOT be constructed in standard programming. Instead, the class should be used procedurally: PoolUtils.adapt(aPool);. This constructor is public to permit tools that require a JavaBean instance to operate.

Method Detail

adapt

public static PoolableObjectFactory adapt(KeyedPoolableObjectFactory keyedFactory)
                                   throws IllegalArgumentException
Adapt a KeyedPoolableObjectFactory instance to work where a PoolableObjectFactory is needed. This method is the equivalent of calling PoolUtils.adapt(aKeyedPoolableObjectFactory, new Object()).

Parameters:
keyedFactory - the KeyedPoolableObjectFactory to delegate to.
Returns:
a PoolableObjectFactory that delegates to keyedFactory with an internal key.
Throws:
IllegalArgumentException - when keyedFactory is null.
Since:
Pool 1.3
See Also:
adapt(KeyedPoolableObjectFactory, Object)

adapt

public static PoolableObjectFactory adapt(KeyedPoolableObjectFactory keyedFactory,
                                          Object key)
                                   throws IllegalArgumentException
Adapt a KeyedPoolableObjectFactory instance to work where a PoolableObjectFactory is needed using the specified key when delegating.

Parameters:
keyedFactory - the KeyedPoolableObjectFactory to delegate to.
key - the key to use when delegating.
Returns:
a PoolableObjectFactory that delegates to keyedFactory with the specified key.
Throws:
IllegalArgumentException - when keyedFactory or key is null.
Since:
Pool 1.3
See Also:
adapt(KeyedPoolableObjectFactory)

adapt

public static KeyedPoolableObjectFactory adapt(PoolableObjectFactory factory)
                                        throws IllegalArgumentException
Adapt a PoolableObjectFactory instance to work where a KeyedPoolableObjectFactory is needed. The key is ignored.

Parameters:
factory - the PoolableObjectFactory to delegate to.
Returns:
a KeyedPoolableObjectFactory that delegates to factory ignoring the key.
Throws:
IllegalArgumentException - when factory is null.
Since:
Pool 1.3

adapt

public static ObjectPool adapt(KeyedObjectPool keyedPool)
                        throws IllegalArgumentException
Adapt a KeyedObjectPool instance to work where an ObjectPool is needed. This is the equivalent of calling PoolUtils.adapt(aKeyedObjectPool, new Object()).

Parameters:
keyedPool - the KeyedObjectPool to delegate to.
Returns:
an ObjectPool that delegates to keyedPool with an internal key.
Throws:
IllegalArgumentException - when keyedPool is null.
Since:
Pool 1.3
See Also:
adapt(KeyedObjectPool, Object)

adapt

public static ObjectPool adapt(KeyedObjectPool keyedPool,
                               Object key)
                        throws IllegalArgumentException
Adapt a KeyedObjectPool instance to work where an ObjectPool is needed using the specified key when delegating.

Parameters:
keyedPool - the KeyedObjectPool to delegate to.
key - the key to use when delegating.
Returns:
an ObjectPool that delegates to keyedPool with the specified key.
Throws:
IllegalArgumentException - when keyedPool or key is null.
Since:
Pool 1.3
See Also:
adapt(KeyedObjectPool)

adapt

public static KeyedObjectPool adapt(ObjectPool pool)
                             throws IllegalArgumentException
Adapt an ObjectPool to work where an KeyedObjectPool is needed. The key is ignored.

Parameters:
pool - the ObjectPool to delegate to.
Returns:
a KeyedObjectPool that delegates to pool ignoring the key.
Throws:
IllegalArgumentException - when pool is null.
Since:
Pool 1.3

checkedPool

public static ObjectPool checkedPool(ObjectPool pool,
                                     Class type)
Wraps an ObjectPool and dynamically checks the type of objects borrowed and returned to the pool. If an object is passed to the pool that isn't of type type a ClassCastException will be thrown.

Parameters:
pool - the pool to enforce type safety on
type - the class type to enforce.
Returns:
an ObjectPool that will only allow objects of type
Since:
Pool 1.3

checkedPool

public static KeyedObjectPool checkedPool(KeyedObjectPool keyedPool,
                                          Class type)
Wraps a KeyedObjectPool and dynamically checks the type of objects borrowed and returned to the keyedPool. If an object is passed to the keyedPool that isn't of type type a ClassCastException will be thrown.

Parameters:
keyedPool - the keyedPool to enforce type safety on
type - the class type to enforce.
Returns:
a KeyedObjectPool that will only allow objects of type
Since:
Pool 1.3

checkMinIdle

public static TimerTask checkMinIdle(ObjectPool pool,
                                     int minIdle,
                                     long period)
                              throws IllegalArgumentException
Periodically check the idle object count for the pool. At most one idle object will be added per period. If there is an exception when calling ObjectPool.addObject() then no more checks will be performed.

Parameters:
pool - the pool to check periodically.
minIdle - if the ObjectPool.getNumIdle() is less than this then add an idle object.
period - the frequency to check the number of idle objects in a pool, see Timer.schedule(TimerTask, long, long).
Returns:
the TimerTask that will periodically check the pools idle object count.
Throws:
IllegalArgumentException - when pool is null or when minIdle is negative or when period isn't valid for Timer.schedule(TimerTask, long, long).
Since:
Pool 1.3

checkMinIdle

public static TimerTask checkMinIdle(KeyedObjectPool keyedPool,
                                     Object key,
                                     int minIdle,
                                     long period)
                              throws IllegalArgumentException
Periodically check the idle object count for the key in the keyedPool. At most one idle object will be added per period. If there is an exception when calling KeyedObjectPool.addObject(Object) then no more checks for that key will be performed.

Parameters:
keyedPool - the keyedPool to check periodically.
key - the key to check the idle count of.
minIdle - if the KeyedObjectPool.getNumIdle(Object) is less than this then add an idle object.
period - the frequency to check the number of idle objects in a keyedPool, see Timer.schedule(TimerTask, long, long).
Returns:
the TimerTask that will periodically check the pools idle object count.
Throws:
IllegalArgumentException - when keyedPool, key is null or when minIdle is negative or when period isn't valid for Timer.schedule(TimerTask, long, long).
Since:
Pool 1.3

checkMinIdle

public static Map checkMinIdle(KeyedObjectPool keyedPool,
                               Collection keys,
                               int minIdle,
                               long period)
                        throws IllegalArgumentException
Periodically check the idle object count for each key in the Collection keys in the keyedPool. At most one idle object will be added per period.

Parameters:
keyedPool - the keyedPool to check periodically.
keys - a collection of keys to check the idle object count.
minIdle - if the KeyedObjectPool.getNumIdle(Object) is less than this then add an idle object.
period - the frequency to check the number of idle objects in a keyedPool, see Timer.schedule(TimerTask, long, long).
Returns:
a Map of key and TimerTask pairs that will periodically check the pools idle object count.
Throws:
IllegalArgumentException - when keyedPool, keys, or any of the values in the collection is null or when minIdle is negative or when period isn't valid for Timer.schedule(TimerTask, long, long).
Since:
Pool 1.3
See Also:
checkMinIdle(KeyedObjectPool, Object, int, long)

prefill

public static void prefill(ObjectPool pool,
                           int count)
                    throws Exception,
                           IllegalArgumentException
Call addObject() on pool count number of times.

Parameters:
pool - the pool to prefill.
count - the number of idle objects to add.
Throws:
Exception - when ObjectPool.addObject() fails.
IllegalArgumentException - when pool is null.
Since:
Pool 1.3

prefill

public static void prefill(KeyedObjectPool keyedPool,
                           Object key,
                           int count)
                    throws Exception,
                           IllegalArgumentException
Call addObject(Object) on keyedPool with key count number of times.

Parameters:
keyedPool - the keyedPool to prefill.
key - the key to add objects for.
count - the number of idle objects to add for key.
Throws:
Exception - when KeyedObjectPool.addObject(Object) fails.
IllegalArgumentException - when keyedPool or key is null.
Since:
Pool 1.3

prefill

public static void prefill(KeyedObjectPool keyedPool,
                           Collection keys,
                           int count)
                    throws Exception,
                           IllegalArgumentException
Call addObject(Object) on keyedPool with each key in keys for count number of times. This has the same effect as calling prefill(KeyedObjectPool, Object, int) for each key in the keys collection.

Parameters:
keyedPool - the keyedPool to prefill.
keys - Collection of keys to add objects for.
count - the number of idle objects to add for each key.
Throws:
Exception - when KeyedObjectPool.addObject(Object) fails.
IllegalArgumentException - when keyedPool, keys, or any value in keys is null.
Since:
Pool 1.3
See Also:
prefill(KeyedObjectPool, Object, int)

synchronizedPool

public static ObjectPool synchronizedPool(ObjectPool pool)
Returns a synchronized (thread-safe) ObjectPool backed by the specified ObjectPool.

Note: This should not be used on pool implementations that already provide proper synchronization such as the pools provided in the Commons Pool library. Wrapping a pool that waits for poolable objects to be returned before allowing another one to be borrowed with another layer of synchronization will cause liveliness issues or a deadlock.

Parameters:
pool - the ObjectPool to be "wrapped" in a synchronized ObjectPool.
Returns:
a synchronized view of the specified ObjectPool.
Since:
Pool 1.3

synchronizedPool

public static KeyedObjectPool synchronizedPool(KeyedObjectPool keyedPool)
Returns a synchronized (thread-safe) KeyedObjectPool backed by the specified KeyedObjectPool.

Note: This should not be used on pool implementations that already provide proper synchronization such as the pools provided in the Commons Pool library. Wrapping a pool that waits for poolable objects to be returned before allowing another one to be borrowed with another layer of synchronization will cause liveliness issues or a deadlock.

Parameters:
keyedPool - the KeyedObjectPool to be "wrapped" in a synchronized KeyedObjectPool.
Returns:
a synchronized view of the specified KeyedObjectPool.
Since:
Pool 1.3

synchronizedPoolableFactory

public static PoolableObjectFactory synchronizedPoolableFactory(PoolableObjectFactory factory)
Returns a synchronized (thread-safe) PoolableObjectFactory backed by the specified PoolableObjectFactory.

Parameters:
factory - the PoolableObjectFactory to be "wrapped" in a synchronized PoolableObjectFactory.
Returns:
a synchronized view of the specified PoolableObjectFactory.
Since:
Pool 1.3

synchronizedPoolableFactory

public static KeyedPoolableObjectFactory synchronizedPoolableFactory(KeyedPoolableObjectFactory keyedFactory)
Returns a synchronized (thread-safe) KeyedPoolableObjectFactory backed by the specified KeyedPoolableObjectFactory.

Parameters:
keyedFactory - the KeyedPoolableObjectFactory to be "wrapped" in a synchronized KeyedPoolableObjectFactory.
Returns:
a synchronized view of the specified KeyedPoolableObjectFactory.
Since:
Pool 1.3

erodingPool

public static ObjectPool erodingPool(ObjectPool pool)
Returns a pool that adaptively decreases it's size when idle objects are no longer needed. This is intended as an always thread-safe alternative to using an idle object evictor provided by many pool implementations. This is also an effective way to shrink FIFO ordered pools that experience load spikes.

Parameters:
pool - the ObjectPool to be decorated so it shrinks it's idle count when possible.
Returns:
a pool that adaptively decreases it's size when idle objects are no longer needed.
Since:
Pool 1.4
See Also:
erodingPool(ObjectPool, float)

erodingPool

public static ObjectPool erodingPool(ObjectPool pool,
                                     float factor)
Returns a pool that adaptively decreases it's size when idle objects are no longer needed. This is intended as an always thread-safe alternative to using an idle object evictor provided by many pool implementations. This is also an effective way to shrink FIFO ordered pools that experience load spikes.

The factor parameter provides a mechanism to tweak the rate at which the pool tries to shrink it's size. Values between 0 and 1 cause the pool to try to shrink it's size more often. Values greater than 1 cause the pool to less frequently try to shrink it's size.

Parameters:
pool - the ObjectPool to be decorated so it shrinks it's idle count when possible.
factor - a positive value to scale the rate at which the pool tries to reduce it's size. If 0 < factor < 1 then the pool shrinks more aggressively. If 1 < factor then the pool shrinks less aggressively.
Returns:
a pool that adaptively decreases it's size when idle objects are no longer needed.
Since:
Pool 1.4
See Also:
erodingPool(ObjectPool)

erodingPool

public static KeyedObjectPool erodingPool(KeyedObjectPool keyedPool)
Returns a pool that adaptively decreases it's size when idle objects are no longer needed. This is intended as an always thread-safe alternative to using an idle object evictor provided by many pool implementations. This is also an effective way to shrink FIFO ordered pools that experience load spikes.

Parameters:
keyedPool - the KeyedObjectPool to be decorated so it shrinks it's idle count when possible.
Returns:
a pool that adaptively decreases it's size when idle objects are no longer needed.
Since:
Pool 1.4
See Also:
erodingPool(KeyedObjectPool, float), erodingPool(KeyedObjectPool, float, boolean)

erodingPool

public static KeyedObjectPool erodingPool(KeyedObjectPool keyedPool,
                                          float factor)
Returns a pool that adaptively decreases it's size when idle objects are no longer needed. This is intended as an always thread-safe alternative to using an idle object evictor provided by many pool implementations. This is also an effective way to shrink FIFO ordered pools that experience load spikes.

The factor parameter provides a mechanism to tweak the rate at which the pool tries to shrink it's size. Values between 0 and 1 cause the pool to try to shrink it's size more often. Values greater than 1 cause the pool to less frequently try to shrink it's size.

Parameters:
keyedPool - the KeyedObjectPool to be decorated so it shrinks it's idle count when possible.
factor - a positive value to scale the rate at which the pool tries to reduce it's size. If 0 < factor < 1 then the pool shrinks more aggressively. If 1 < factor then the pool shrinks less aggressively.
Returns:
a pool that adaptively decreases it's size when idle objects are no longer needed.
Since:
Pool 1.4
See Also:
erodingPool(KeyedObjectPool, float, boolean)

erodingPool

public static KeyedObjectPool erodingPool(KeyedObjectPool keyedPool,
                                          float factor,
                                          boolean perKey)
Returns a pool that adaptively decreases it's size when idle objects are no longer needed. This is intended as an always thread-safe alternative to using an idle object evictor provided by many pool implementations. This is also an effective way to shrink FIFO ordered pools that experience load spikes.

The factor parameter provides a mechanism to tweak the rate at which the pool tries to shrink it's size. Values between 0 and 1 cause the pool to try to shrink it's size more often. Values greater than 1 cause the pool to less frequently try to shrink it's size.

The perKey parameter determines if the pool shrinks on a whole pool basis or a per key basis. When perKey is false, the keys do not have an effect on the rate at which the pool tries to shrink it's size. When perKey is true, each key is shrunk independently.

Parameters:
keyedPool - the KeyedObjectPool to be decorated so it shrinks it's idle count when possible.
factor - a positive value to scale the rate at which the pool tries to reduce it's size. If 0 < factor < 1 then the pool shrinks more aggressively. If 1 < factor then the pool shrinks less aggressively.
perKey - when true, each key is treated independently.
Returns:
a pool that adaptively decreases it's size when idle objects are no longer needed.
Since:
Pool 1.4
See Also:
erodingPool(KeyedObjectPool), erodingPool(KeyedObjectPool, float)
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