org.apache.commons.pool.impl
Class SoftReferenceObjectPool

java.lang.Object
  org.apache.commons.pool.BaseObjectPool
      org.apache.commons.pool.impl.SoftReferenceObjectPool

All Implemented Interfaces:

ObjectPool

public class SoftReferenceObjectPool
extends BaseObjectPool
implements ObjectPool

A SoftReference based ObjectPool.

Since:

Pool 1.0

Version:

$Revision: 607137 $ $Date: 2007-12-27 16:06:49 -0700 (Thu, 27 Dec 2007) $

Constructor Summary

SoftReferenceObjectPool()
Create a SoftReferenceObjectPool without a factory.

SoftReferenceObjectPool(PoolableObjectFactory factory)
Create a SoftReferenceObjectPool with the specified factory.

SoftReferenceObjectPool(PoolableObjectFactory factory, int initSize)
Deprecated. because this is a SoftReference pool, prefilled idle obejects may be garbage collected before they are used. To be removed in Pool 3.0.

Method Summary

void	addObject() Create an object, and place it into the pool.
Object	borrowObject() Obtains an instance from this pool.
void	clear() Clears any objects sitting idle in the pool.
void	close() Close this pool.
int	getNumActive() Return the number of instances currently borrowed from this pool.
int	getNumIdle() Returns an approximation not less than the of the number of idle instances in the pool.
void	invalidateObject(Object 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.
void	returnObject(Object obj) Return an instance to the pool.
void	setFactory(PoolableObjectFactory factory) Sets the factory this pool uses to create new instances.

Methods inherited from class org.apache.commons.pool.BaseObjectPool

assertOpen, isClosed

Methods inherited from class java.lang.Object

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

Constructor Detail

SoftReferenceObjectPool

public SoftReferenceObjectPool()

Create a SoftReferenceObjectPool without a factory. setFactory should be called before any attempts to use the pool are made. Generally speaking you should prefer the SoftReferenceObjectPool(PoolableObjectFactory) constructor.

See Also:

SoftReferenceObjectPool(PoolableObjectFactory)

SoftReferenceObjectPool

public SoftReferenceObjectPool(PoolableObjectFactory factory)

Create a SoftReferenceObjectPool with the specified factory.

Parameters:

factory - object factory to use.

SoftReferenceObjectPool

public SoftReferenceObjectPool(PoolableObjectFactory factory,
                               int initSize)
                        throws Exception,
                               IllegalArgumentException

Deprecated. because this is a SoftReference pool, prefilled idle obejects may be garbage collected before they are used. To be removed in Pool 3.0.

Create a SoftReferenceObjectPool with the specified factory and initial idle object count.

Parameters:

factory - object factory to use.

initSize - initial size to attempt to prefill the pool.

Throws:

Exception - when there is a problem prefilling the pool.

IllegalArgumentException - when factory is null.

Method Detail

borrowObject

public Object borrowObject()
                    throws Exception

Description copied from interface: ObjectPool

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

Specified by:

borrowObject in class BaseObjectPool

Returns:

an instance from this pool.

Throws:

IllegalStateException - after close has been called on this pool.

Exception - when makeObject throws an exception.

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

returnObject

public void returnObject(Object obj)
                  throws Exception

Description copied from interface: ObjectPool

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

Specified by:

returnObject in interface ObjectPool

Specified by:

returnObject in class BaseObjectPool

Parameters:

obj - a borrowed instance to be returned.

Throws:

Exception - deprecated: as of Pool 2.0 pool implementations should swallow exceptions that occur when a poolable object is returned. For future source compatability implementations of this method should not even declare that they throw any exception.

invalidateObject

public void invalidateObject(Object obj)
                      throws Exception

Description copied from interface: ObjectPool

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

Specified by:

invalidateObject in class BaseObjectPool

Parameters:

obj - a borrowed instance to be disposed.

Throws:

Exception - deprecated: as of Pool 2.0 pool implementations should swallow exceptions that occur when a poolable object is returned. For future source compatability implementations of this method should not even declare that they throw any exception.

addObject

public void addObject()
               throws Exception

Create an object, and place it into the pool. addObject() is useful for "pre-loading" a pool with idle objects.

Specified by:

addObject in interface ObjectPool

Overrides:

addObject in class BaseObjectPool

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()

Returns an approximation not less than the of the number of idle instances in the pool.

Specified by:

getNumIdle in interface ObjectPool

Overrides:

getNumIdle in class BaseObjectPool

Returns:

a negative value.

getNumActive

public int getNumActive()

Return the number of instances currently borrowed from this pool.

Specified by:

getNumActive in interface ObjectPool

Overrides:

getNumActive in class BaseObjectPool

Returns:

the number of instances currently borrowed from this pool

clear

public void clear()

Clears any objects sitting idle in the pool.

Specified by:

clear in interface ObjectPool

Overrides:

clear in class BaseObjectPool

close

public void close()
           throws Exception

Description copied from class: BaseObjectPool

Close this pool. This affects the behavior of isClosed and assertOpen.

Specified by:

close in interface ObjectPool

Overrides:

close in class BaseObjectPool

Throws:

Exception - deprecated: implementations should silently fail if not all resources can be freed.

setFactory

public void setFactory(PoolableObjectFactory factory)
                throws IllegalStateException

Sets the factory this pool uses to create new instances. Trying to change the factory while there are borrowed objects will throw an IllegalStateException.

Specified by:

setFactory in interface ObjectPool

Overrides:

setFactory in class BaseObjectPool

Parameters:

factory - the PoolableObjectFactory used to create new instances.

Throws:

IllegalStateException - when the factory cannot be set at this time