Package org.apache.commons.pool

Class PoolUtils.ErodingObjectPool<T>

java.lang.Object

org.apache.commons.pool.PoolUtils.ErodingObjectPool<T>

All Implemented Interfaces:

ObjectPool<T>

Enclosing class:

PoolUtils

private static class PoolUtils.ErodingObjectPool<T>
extends Object
implements ObjectPool<T>

Decorates an object pool, adding "eroding" behavior. Based on the configured erosion factor, objects returning to the pool may be invalidated instead of being added to idle capacity.

Field Summary

Fields

Modifier and Type	Field	Description
private final PoolUtils.ErodingFactor	factor	Erosion factor
private final ObjectPool<T>	pool	Underlying object pool

Constructor Summary

Constructors

Constructor	Description
ErodingObjectPool(ObjectPool<T> pool, float factor)	Create an ErodingObjectPool wrapping the given pool using the specified erosion factor.

Method Summary

Modifier and Type	Method	Description
void	addObject()	Create an object using the factory or other implementation dependent mechanism, passivate it, and then place it in the idle object pool.
T	borrowObject()	Obtains an instance from this pool.
void	clear()	Clears any objects sitting idle in the pool, releasing any associated resources (optional operation).
void	close()	Close this pool, and free any resources associated with it.
int	getNumActive()	Return the number of instances currently borrowed from this pool (optional operation).
int	getNumIdle()	Return the number of instances currently idle in this pool (optional operation).
void	invalidateObject(T obj)	Invalidates an object from the pool.
void	returnObject(T obj)	Returns obj to the pool, unless erosion is triggered, in which case obj is invalidated.
void	setFactory(PoolableObjectFactory<T> factory)	Deprecated. to be removed in pool 2.0
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

pool

private final ObjectPool<T> pool

Underlying object pool

factor

private final PoolUtils.ErodingFactor factor

Erosion factor

Constructor Details

ErodingObjectPool

public ErodingObjectPool(ObjectPool<T> pool,
 float factor)

Create an ErodingObjectPool wrapping the given pool using the specified erosion factor.

Parameters:

pool - underlying pool

factor - erosion factor - determines the frequency of erosion events

See Also:

• factor

Method Details

borrowObject

public T borrowObject()
               throws Exception,
NoSuchElementException,
IllegalStateException

Obtains an instance from this pool.

Instances returned from this method will have been either newly created with makeObject or will be a previously idle object and have been activated with activateObject and then validated with validateObject.

By contract, clients must return the borrowed instance using returnObject, invalidateObject, or a related method as defined in an implementation or sub-interface.

The behaviour of this method when the pool has been exhausted is not strictly specified (although it may be specified by implementations). Older versions of this method would return null to indicate exhaustion, newer versions are encouraged to throw a NoSuchElementException.

Specified by:

borrowObject in interface ObjectPool<T>

Returns:

an instance from this pool.

Throws:

Exception - when makeObject throws an exception.

NoSuchElementException - when the pool is exhausted and cannot or will not return another instance.

IllegalStateException - after close has been called on this pool.

returnObject

public void returnObject(T obj)

Returns obj to the pool, unless erosion is triggered, in which case obj is invalidated. Erosion is triggered when there are idle instances in the pool and more than the erosion factor-determined time has elapsed since the last returnObject activation.

Specified by:

returnObject in interface ObjectPool<T>

Parameters:

obj - object to return or invalidate

See Also:

• factor

invalidateObject

public void invalidateObject(T obj)

Invalidates an object from the pool.

By contract, obj must have been obtained using borrowObject or a related method as defined in an implementation or sub-interface.

This method should be used when an object that has been borrowed is determined (due to an exception or other problem) to be invalid.

Specified by:

invalidateObject in interface ObjectPool<T>

Parameters:

obj - a borrowed instance to be disposed.

addObject

public void addObject()
               throws Exception,
IllegalStateException,
UnsupportedOperationException

Create an object using the factory or other implementation dependent mechanism, passivate it, and then place it in the idle object pool. addObject is useful for "pre-loading" a pool with idle objects. (Optional operation).

Specified by:

addObject in interface ObjectPool<T>

Throws:

Exception - when PoolableObjectFactory.makeObject() fails.

IllegalStateException - after ObjectPool.close() has been called on this pool.

UnsupportedOperationException - when this pool cannot add new idle objects.

getNumIdle

public int getNumIdle()
               throws UnsupportedOperationException

Return the number of instances currently idle in this pool (optional operation). This may be considered an approximation of the number of objects that can be borrowed without creating any new instances. Returns a negative value if this information is not available.

Specified by:

getNumIdle in interface ObjectPool<T>

Returns:

the number of instances currently idle in this pool or a negative value if unsupported

Throws:

UnsupportedOperationException - deprecated: if this implementation does not support the operation

getNumActive

public int getNumActive()
                 throws UnsupportedOperationException

Return the number of instances currently borrowed from this pool (optional operation). Returns a negative value if this information is not available.

Specified by:

getNumActive in interface ObjectPool<T>

Returns:

the number of instances currently borrowed from this pool or a negative value if unsupported

Throws:

UnsupportedOperationException - deprecated: if this implementation does not support the operation

clear

public void clear()
           throws Exception,
UnsupportedOperationException

Clears any objects sitting idle in the pool, releasing any associated resources (optional operation). Idle objects cleared must be destroyed.

Specified by:

clear in interface ObjectPool<T>

Throws:

UnsupportedOperationException - if this implementation does not support the operation

Exception

close

public void close()

Close this pool, and free any resources associated with it.

Calling ObjectPool.addObject() or ObjectPool.borrowObject() after invoking this method on a pool will cause them to throw an IllegalStateException.

Specified by:

close in interface ObjectPool<T>

setFactory

@Deprecated
public void setFactory(PoolableObjectFactory<T> factory)
                throws IllegalStateException,
UnsupportedOperationException

Deprecated.

to be removed in pool 2.0

Sets the factory this pool uses to create new instances (optional operation). Trying to change the factory after a pool has been used will frequently throw an UnsupportedOperationException. It is up to the pool implementation to determine when it is acceptable to call this method.

Specified by:

setFactory in interface ObjectPool<T>

Parameters:

factory - the PoolableObjectFactory used to create new instances.

Throws:

IllegalStateException - when the factory cannot be set at this time

UnsupportedOperationException - if this implementation does not support the operation

toString

public String toString()

Overrides:

toString in class Object