org.apache.commons.pool.impl
Class StackObjectPool

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

All Implemented Interfaces:

ObjectPool

public class StackObjectPool
extends BaseObjectPool
implements ObjectPool

A simple, Stack-based ObjectPool implementation.

Given a PoolableObjectFactory, this class will maintain a simple pool of instances. A finite number of "sleeping" or idle instances is enforced, but when the pool is empty, new instances are created to support the new load. Hence this class places no limit on the number of "active" instances created by the pool, but is quite useful for re-using Objects without introducing artificial limits.

Since:

Pool 1.0

Version:

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

Field Summary

protected PoolableObjectFactory	_factory My PoolableObjectFactory.
protected int	_maxSleeping The cap on the number of "sleeping" instances in the pool.
protected int	_numActive Number of object borrowed but not yet returned to the pool.
protected Stack	_pool My pool.
protected static int	DEFAULT_INIT_SLEEPING_CAPACITY The default initial size of the pool (this specifies the size of the container, it does not cause the pool to be pre-populated.)
protected static int	DEFAULT_MAX_SLEEPING The default cap on the number of "sleeping" instances in the pool.

Constructor Summary

StackObjectPool()
Create a new pool using no factory.

StackObjectPool(int maxIdle)
Create a new pool using no factory.

StackObjectPool(int maxIdle, int initIdleCapacity)
Create a new pool using no factory.

StackObjectPool(PoolableObjectFactory factory)
Create a new StackObjectPool using the specified factory to create new instances.

StackObjectPool(PoolableObjectFactory factory, int maxIdle)
Create a new SimpleObjectPool using the specified factory to create new instances, capping the number of "sleeping" instances to max.

StackObjectPool(PoolableObjectFactory factory, int maxIdle, int initIdleCapacity)
Create a new SimpleObjectPool using the specified factory to create new instances, capping the number of "sleeping" instances to max, and initially allocating a container capable of containing at least init instances.

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, and free any resources associated with it.
int	getNumActive() Return the number of instances currently borrowed from this pool.
int	getNumIdle() Return the number of instances currently idle in this 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

Field Detail

DEFAULT_MAX_SLEEPING

protected static final int DEFAULT_MAX_SLEEPING

The default cap on the number of "sleeping" instances in the pool.

See Also:

Constant Field Values

DEFAULT_INIT_SLEEPING_CAPACITY

protected static final int DEFAULT_INIT_SLEEPING_CAPACITY

The default initial size of the pool (this specifies the size of the container, it does not cause the pool to be pre-populated.)

See Also:

Constant Field Values

_pool

protected Stack _pool

My pool.

_factory

protected PoolableObjectFactory _factory

My PoolableObjectFactory.

_maxSleeping

protected int _maxSleeping

The cap on the number of "sleeping" instances in the pool.

_numActive

protected int _numActive

Number of object borrowed but not yet returned to the pool.

Constructor Detail

StackObjectPool

public StackObjectPool()

Create a new pool using no factory. Clients must first set the factory else this pool will not behave correctly. Clients may first populate the pool using returnObject(java.lang.Object) before they can be borrowed but this useage is discouraged.

See Also:

StackObjectPool(PoolableObjectFactory)

StackObjectPool

public StackObjectPool(int maxIdle)

Create a new pool using no factory. Clients must first set the factory else this pool will not behave correctly. Clients may first populate the pool using returnObject(java.lang.Object) before they can be borrowed but this useage is discouraged.

Parameters:

maxIdle - cap on the number of "sleeping" instances in the pool

See Also:

StackObjectPool(PoolableObjectFactory, int)

StackObjectPool

public StackObjectPool(int maxIdle,
                       int initIdleCapacity)

Create a new pool using no factory. Clients must first set the factory else this pool will not behave correctly. Clients may first populate the pool using returnObject(java.lang.Object) before they can be borrowed but this useage is discouraged.

Parameters:

maxIdle - cap on the number of "sleeping" instances in the pool

initIdleCapacity - initial size of the pool (this specifies the size of the container, it does not cause the pool to be pre-populated.)

See Also:

StackObjectPool(PoolableObjectFactory, int, int)

StackObjectPool

public StackObjectPool(PoolableObjectFactory factory)

Create a new StackObjectPool using the specified factory to create new instances.

Parameters:

factory - the PoolableObjectFactory used to populate the pool

StackObjectPool

public StackObjectPool(PoolableObjectFactory factory,
                       int maxIdle)

Create a new SimpleObjectPool using the specified factory to create new instances, capping the number of "sleeping" instances to max.

Parameters:

factory - the PoolableObjectFactory used to populate the pool

maxIdle - cap on the number of "sleeping" instances in the pool

StackObjectPool

public StackObjectPool(PoolableObjectFactory factory,
                       int maxIdle,
                       int initIdleCapacity)

Create a new SimpleObjectPool using the specified factory to create new instances, capping the number of "sleeping" instances to max, and initially allocating a container capable of containing at least init instances.

Parameters:

factory - the PoolableObjectFactory used to populate the pool

maxIdle - cap on the number of "sleeping" instances in the pool

initIdleCapacity - initial size of the pool (this specifies the size of the container, it does not cause the pool to be pre-populated.)

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.

getNumIdle

public int getNumIdle()

Return the number of instances currently idle in this pool.

Specified by:

getNumIdle in interface ObjectPool

Overrides:

getNumIdle in class BaseObjectPool

Returns:

the number of instances currently idle in this pool

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

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

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

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.

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 the _factory has a problem creating an object.

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