Class PoolUtils

java.lang.Object
org.apache.tomcat.dbcp.pool2.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:
2.0

  • 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

    • checkMinIdle

      public static <K, V> Map<K,TimerTask> checkMinIdle(KeyedObjectPool<K,V> keyedPool, Collection<K> keys, int minIdle, long periodMillis) 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 the pool key
      V - the type of pool entries
      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.
      periodMillis - the frequency in milliseconds 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).
      See Also:

    • checkMinIdle

      public static <K, V> TimerTask checkMinIdle(KeyedObjectPool<K,V> keyedPool, K key, int minIdle, long periodMillis) 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 the pool key
      V - the type of pool entries
      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.
      periodMillis - the frequency in milliseconds 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).

    • checkMinIdle

      public static <T> TimerTask checkMinIdle(ObjectPool<T> pool, int minIdle, long periodMillis) 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 objects in the pool
      Parameters:
      pool - the pool to check periodically.
      minIdle - if the ObjectPool.getNumIdle() is less than this then add an idle object.
      periodMillis - the frequency in milliseconds 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)

    • 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:
      VirtualMachineError - if that is passed in

    • erodingPool

      public static <K, V> KeyedObjectPool<K,V> erodingPool(KeyedObjectPool<K,V> keyedPool)
      Returns a pool that adaptively decreases its 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 the pool key
      V - the type of pool entries
      Parameters:
      keyedPool - the KeyedObjectPool to be decorated so it shrinks its idle count when possible.
      Returns:
      a pool that adaptively decreases its size when idle objects are no longer needed.
      Throws:
      IllegalArgumentException - when keyedPool is null.
      See Also:

    • erodingPool

      public static <K, V> KeyedObjectPool<K,V> erodingPool(KeyedObjectPool<K,V> keyedPool, float factor)
      Returns a pool that adaptively decreases its 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 its size. Values between 0 and 1 cause the pool to try to shrink its size more often. Values greater than 1 cause the pool to less frequently try to shrink its size.

      Type Parameters:
      K - the type of the pool key
      V - the type of pool entries
      Parameters:
      keyedPool - the KeyedObjectPool to be decorated so it shrinks its idle count when possible.
      factor - a positive value to scale the rate at which the pool tries to reduce its 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 its size when idle objects are no longer needed.
      Throws:
      IllegalArgumentException - when keyedPool is null or when factor is not positive.
      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 its 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 its size. Values between 0 and 1 cause the pool to try to shrink its size more often. Values greater than 1 cause the pool to less frequently try to shrink its 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 its size. When perKey is true, each key is shrunk independently.

      Type Parameters:
      K - the type of the pool key
      V - the type of pool entries
      Parameters:
      keyedPool - the KeyedObjectPool to be decorated so it shrinks its idle count when possible.
      factor - a positive value to scale the rate at which the pool tries to reduce its 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 its size when idle objects are no longer needed.
      Throws:
      IllegalArgumentException - when keyedPool is null or when factor is not positive.
      See Also:

    • erodingPool

      public static <T> ObjectPool<T> erodingPool(ObjectPool<T> pool)
      Returns a pool that adaptively decreases its 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 objects in the pool
      Parameters:
      pool - the ObjectPool to be decorated so it shrinks its idle count when possible.
      Returns:
      a pool that adaptively decreases its size when idle objects are no longer needed.
      Throws:
      IllegalArgumentException - when pool is null.
      See Also:

    • erodingPool

      public static <T> ObjectPool<T> erodingPool(ObjectPool<T> pool, float factor)
      Returns a pool that adaptively decreases its 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 its size. Values between 0 and 1 cause the pool to try to shrink its size more often. Values greater than 1 cause the pool to less frequently try to shrink its size.

      Type Parameters:
      T - the type of objects in the pool
      Parameters:
      pool - the ObjectPool to be decorated so it shrinks its idle count when possible.
      factor - a positive value to scale the rate at which the pool tries to reduce its 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 its size when idle objects are no longer needed.
      Throws:
      IllegalArgumentException - when pool is null or when factor is not positive.
      See Also:

    • prefill

      @Deprecated public static <K, V> void prefill(KeyedObjectPool<K,V> keyedPool, Collection<K> keys, int count) throws Exception, IllegalArgumentException
      Deprecated.
      Use KeyedObjectPool.addObjects(Collection, int).
      Calls KeyedObjectPool.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 the pool key
      V - the type of pool entries
      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.
      See Also:

    • prefill

      @Deprecated public static <K, V> void prefill(KeyedObjectPool<K,V> keyedPool, K key, int count) throws Exception, IllegalArgumentException
      Deprecated.
      Use KeyedObjectPool.addObjects(Object, int).
      Calls KeyedObjectPool.addObject(Object) on keyedPool with key count number of times.
      Type Parameters:
      K - the type of the pool key
      V - the type of pool entries
      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.

    • prefill

      @Deprecated public static <T> void prefill(ObjectPool<T> pool, int count) throws Exception
      Deprecated.
      Use ObjectPool.addObjects(int).
      Calls ObjectPool.addObject() on pool count number of times.
      Type Parameters:
      T - the type of objects in the pool
      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.

    • synchronizedKeyedPooledFactory

      public static <K, V> KeyedPooledObjectFactory<K,V> synchronizedKeyedPooledFactory(KeyedPooledObjectFactory<K,V> keyedFactory)
      Returns a synchronized (thread-safe) KeyedPooledObjectFactory backed by the specified KeyedPooledObjectFactory.
      Type Parameters:
      K - the type of the pool key
      V - the type of pool entries
      Parameters:
      keyedFactory - the KeyedPooledObjectFactory to be "wrapped" in a synchronized KeyedPooledObjectFactory.
      Returns:
      a synchronized view of the specified KeyedPooledObjectFactory.

    • 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 the pool key
      V - the type of pool entries
      Parameters:
      keyedPool - the KeyedObjectPool to be "wrapped" in a synchronized KeyedObjectPool.
      Returns:
      a synchronized view of the specified KeyedObjectPool.

    • 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 objects in the pool
      Parameters:
      pool - the ObjectPool to be "wrapped" in a synchronized ObjectPool.
      Returns:
      a synchronized view of the specified ObjectPool.
      Throws:
      IllegalArgumentException - when pool is null.

    • synchronizedPooledFactory

      public static <T> PooledObjectFactory<T> synchronizedPooledFactory(PooledObjectFactory<T> factory)
      Returns a synchronized (thread-safe) PooledObjectFactory backed by the specified PooledObjectFactory.
      Type Parameters:
      T - the type of objects in the pool
      Parameters:
      factory - the PooledObjectFactory to be "wrapped" in a synchronized PooledObjectFactory.
      Returns:
      a synchronized view of the specified PooledObjectFactory.