Package org.apache.commons.pool

Class PoolUtils

java.lang.Object
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: 1222670 $ $Date: 2011-12-23 08:18:25 -0500 (Fri, 23 Dec 2011) $
Author:
Sandy McArthur

  • Constructor Details

    • 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 Details

    • checkRethrow

      public static void checkRethrow(Throwable t)
      Should the supplied Throwable be re-thrown (eg if it is an instance of one of the Throwables that should never be swallowed). Used by the pool error handling for operations that throw exceptions that normally need to be ignored.
      Parameters:
      t - The Throwable to check
      Throws:
      ThreadDeath - if that is passed in
      VirtualMachineError - if that is passed in
      Since:
      Pool 1.5.5

    • adapt

      public static <V> PoolableObjectFactory<V> adapt(KeyedPoolableObjectFactory<Object,V> 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()).
      Type Parameters:
      V - the type of 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

      public static <K, V> PoolableObjectFactory<V> adapt(KeyedPoolableObjectFactory<K,V> keyedFactory, K key) throws IllegalArgumentException
      Adapt a KeyedPoolableObjectFactory instance to work where a PoolableObjectFactory is needed using the specified key when delegating.
      Type Parameters:
      K - the type of key
      V - the type of object
      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

      public static <K, V> KeyedPoolableObjectFactory<K,V> adapt(PoolableObjectFactory<V> factory) throws IllegalArgumentException
      Adapt a PoolableObjectFactory instance to work where a KeyedPoolableObjectFactory is needed. The key is ignored.
      Type Parameters:
      K - the type of key
      V - the type of object
      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 <V> ObjectPool<V> adapt(KeyedObjectPool<Object,V> 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()).
      Type Parameters:
      V - the type of 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

      public static <V> ObjectPool<V> adapt(KeyedObjectPool<Object,V> keyedPool, Object key) throws IllegalArgumentException
      Adapt a KeyedObjectPool instance to work where an ObjectPool is needed using the specified key when delegating.
      Type Parameters:
      V - the type of object
      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

      public static <K, V> KeyedObjectPool<K,V> adapt(ObjectPool<V> pool) throws IllegalArgumentException
      Adapt an ObjectPool to work where an KeyedObjectPool is needed. The key is ignored.
      Type Parameters:
      K - the type of key
      V - the type of object
      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 <T> ObjectPool<T> checkedPool(ObjectPool<T> pool, Class<T> 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.
      Type Parameters:
      T - the type of object
      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 <K, V> KeyedObjectPool<K,V> checkedPool(KeyedObjectPool<K,V> keyedPool, Class<V> 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.
      Type Parameters:
      K - the type of key
      V - the type of object
      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 <T> TimerTask checkMinIdle(ObjectPool<T> 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.
      Type Parameters:
      T - the type of object
      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 <K, V> TimerTask checkMinIdle(KeyedObjectPool<K,V> keyedPool, K 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.
      Type Parameters:
      K - the type of key
      V - the type of object
      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 <K, V> Map<K,TimerTask> checkMinIdle(KeyedObjectPool<K,V> keyedPool, Collection<? extends K> 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.
      Type Parameters:
      K - the type of key
      V - the type of object
      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:

    • prefill

      public static <T> void prefill(ObjectPool<T> pool, int count) throws Exception, IllegalArgumentException
      Call addObject() on pool count number of times.
      Type Parameters:
      T - the type of object
      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 <K, V> void prefill(KeyedObjectPool<K,V> keyedPool, K key, int count) throws Exception, IllegalArgumentException
      Call addObject(Object) on keyedPool with key count number of times.
      Type Parameters:
      K - the type of key
      V - the type of object
      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 <K, V> void prefill(KeyedObjectPool<K,V> keyedPool, Collection<? extends K> 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.
      Type Parameters:
      K - the type of key
      V - the type of object
      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:

    • synchronizedPool

      public static <T> ObjectPool<T> synchronizedPool(ObjectPool<T> 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.

      Type Parameters:
      T - the type of object
      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 <K, V> KeyedObjectPool<K,V> synchronizedPool(KeyedObjectPool<K,V> 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.

      Type Parameters:
      K - the type of key
      V - the type of object
      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 <T> PoolableObjectFactory<T> synchronizedPoolableFactory(PoolableObjectFactory<T> factory)
      Returns a synchronized (thread-safe) PoolableObjectFactory backed by the specified PoolableObjectFactory.
      Type Parameters:
      T - the type of object
      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 <K, V> KeyedPoolableObjectFactory<K,V> synchronizedPoolableFactory(KeyedPoolableObjectFactory<K,V> keyedFactory)
      Returns a synchronized (thread-safe) KeyedPoolableObjectFactory backed by the specified KeyedPoolableObjectFactory.
      Type Parameters:
      K - the type of key
      V - the type of object
      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 <T> ObjectPool<T> erodingPool(ObjectPool<T> 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.
      Type Parameters:
      T - the type of object
      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

      public static <T> ObjectPool<T> erodingPool(ObjectPool<T> 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.

      Type Parameters:
      T - the type of object
      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

      public static <K, V> KeyedObjectPool<K,V> erodingPool(KeyedObjectPool<K,V> 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.
      Type Parameters:
      K - the type of key
      V - the type of object
      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

      public static <K, V> KeyedObjectPool<K,V> erodingPool(KeyedObjectPool<K,V> 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.

      Type Parameters:
      K - the type of key
      V - the type of object
      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

      public static <K, V> KeyedObjectPool<K,V> erodingPool(KeyedObjectPool<K,V> 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.

      Type Parameters:
      K - the type of key
      V - the type of object
      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: