org.apache.commons.pool.impl
Class StackKeyedObjectPool

java.lang.Object
  org.apache.commons.pool.BaseKeyedObjectPool
      org.apache.commons.pool.impl.StackKeyedObjectPool

All Implemented Interfaces:

KeyedObjectPool

public class StackKeyedObjectPool
extends BaseKeyedObjectPool
implements KeyedObjectPool

A simple, Stack-based KeyedObjectPool implementation.

Given a KeyedPoolableObjectFactory, this class will maintain a simple pool of instances. A finite number of "sleeping" or inactive 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: 778880 $ $Date: 2009-05-26 16:46:22 -0400 (Tue, 26 May 2009) $

Author:

Rodney Waldhoff, Sandy McArthur

See Also:

Stack

Field Summary

protected HashMap	_activeCount Number of active objects borrowed and not yet returned by pool
protected KeyedPoolableObjectFactory	_factory My KeyedPoolableObjectFactory.
protected int	_initSleepingCapacity The initial capacity of each pool.
protected int	_maxSleeping The cap on the number of "sleeping" instances in each pool.
protected HashMap	_pools My named-set of pools.
protected int	_totActive Total number of object borrowed and not yet retuened for all pools
protected int	_totIdle Total number of objects "sleeping" for all pools
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

StackKeyedObjectPool()
Create a new pool using no factory.

StackKeyedObjectPool(int max)
Create a new pool using no factory.

StackKeyedObjectPool(int max, int init)
Create a new pool using no factory.

StackKeyedObjectPool(KeyedPoolableObjectFactory factory)
Create a new SimpleKeyedObjectPool using the specified factory to create new instances.

StackKeyedObjectPool(KeyedPoolableObjectFactory factory, int max)
Create a new SimpleKeyedObjectPool using the specified factory to create new instances.

StackKeyedObjectPool(KeyedPoolableObjectFactory factory, int max, int init)
Create a new SimpleKeyedObjectPool using the specified factory to create new instances.

Method Summary

void	addObject(Object key) Create an object using the factory, passivate it, and then placed in the idle object pool.
Object	borrowObject(Object key) Obtains an instance from this pool for the specified key.
void	clear() Clears the pool, removing all pooled instances.
void	clear(Object key) Clears the specified pool, removing all pooled instances corresponding to the given key.
void	close() Close this pool, and free any resources associated with it.
int	getNumActive() Returns the total number of instances current borrowed from this pool but not yet returned.
int	getNumActive(Object key) Returns the number of instances currently borrowed from but not yet returned to the pool corresponding to the given key.
int	getNumIdle() Returns the total number of instances currently idle in this pool.
int	getNumIdle(Object key) Returns the number of instances corresponding to the given key currently idle in this pool.
void	invalidateObject(Object key, 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 using a key that is equivalent to the one used to borrow the Object in the first place.
void	returnObject(Object key, Object obj) Return an instance to the pool.
void	setFactory(KeyedPoolableObjectFactory factory) Sets the factory the pool uses to create new instances.
String	toString()

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

assertOpen, isClosed

Methods inherited from class java.lang.Object

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

_pools

protected HashMap _pools

My named-set of pools.

_factory

protected KeyedPoolableObjectFactory _factory

My KeyedPoolableObjectFactory.

_maxSleeping

protected int _maxSleeping

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

_initSleepingCapacity

protected int _initSleepingCapacity

The initial capacity of each pool.

_totActive

protected int _totActive

Total number of object borrowed and not yet retuened for all pools

_totIdle

protected int _totIdle

Total number of objects "sleeping" for all pools

_activeCount

protected HashMap _activeCount

Number of active objects borrowed and not yet returned by pool

Constructor Detail

StackKeyedObjectPool

public StackKeyedObjectPool()

Create a new pool using no factory. Clients must first set the factory or may populate the pool using returnObject before they can be borrowed.

See Also:

StackKeyedObjectPool(KeyedPoolableObjectFactory), setFactory(KeyedPoolableObjectFactory)

StackKeyedObjectPool

public StackKeyedObjectPool(int max)

Create a new pool using no factory. Clients must first set the factory or may populate the pool using returnObject before they can be borrowed.

Parameters:

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

See Also:

StackKeyedObjectPool(KeyedPoolableObjectFactory, int), setFactory(KeyedPoolableObjectFactory)

StackKeyedObjectPool

public StackKeyedObjectPool(int max,
                            int init)

Create a new pool using no factory. Clients must first set the factory or may populate the pool using returnObject before they can be borrowed.

Parameters:

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

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

See Also:

StackKeyedObjectPool(KeyedPoolableObjectFactory, int, int), setFactory(KeyedPoolableObjectFactory)

StackKeyedObjectPool

public StackKeyedObjectPool(KeyedPoolableObjectFactory factory)

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

Parameters:

factory - the KeyedPoolableObjectFactory used to populate the pool

StackKeyedObjectPool

public StackKeyedObjectPool(KeyedPoolableObjectFactory factory,
                            int max)

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

Parameters:

factory - the KeyedPoolableObjectFactory used to populate the pool

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

StackKeyedObjectPool

public StackKeyedObjectPool(KeyedPoolableObjectFactory factory,
                            int max,
                            int init)

Create a new SimpleKeyedObjectPool 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 KeyedPoolableObjectFactory used to populate the pool

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

init - 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(Object key)
                    throws Exception

Description copied from interface: KeyedObjectPool

Obtains an instance from this pool for the specified key.

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 object using returnObject, invalidateObject, or a related method as defined in an implementation or sub-interface, using a key that is equivalent to the one used to borrow the instance in the first place.

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 KeyedObjectPool

Specified by:

borrowObject in class BaseKeyedObjectPool

Parameters:

key - the key used to obtain the object

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 key,
                         Object obj)
                  throws Exception

Description copied from interface: KeyedObjectPool

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 using a key that is equivalent to the one used to borrow the instance in the first place.

Specified by:

returnObject in interface KeyedObjectPool

Specified by:

returnObject in class BaseKeyedObjectPool

Parameters:

key - the key used to obtain the object

obj - a borrowed instance to be returned.

Throws:

Exception

invalidateObject

public void invalidateObject(Object key,
                             Object obj)
                      throws Exception

Description copied from interface: KeyedObjectPool

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 using a key that is equivalent to the one used to borrow the Object in the first place.

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 KeyedObjectPool

Specified by:

invalidateObject in class BaseKeyedObjectPool

Parameters:

key - the key used to obtain the object

obj - a borrowed instance to be returned.

Throws:

Exception

addObject

public void addObject(Object key)
               throws Exception

Create an object using the factory, passivate it, and then placed in the idle object pool. addObject is useful for "pre-loading" a pool with idle objects.

Specified by:

addObject in interface KeyedObjectPool

Overrides:

addObject in class BaseKeyedObjectPool

Parameters:

key - the key a new instance should be added to

Throws:

Exception - when KeyedPoolableObjectFactory.makeObject(java.lang.Object) fails.

IllegalStateException - when no factory has been set or after close() has been called on this pool.

getNumIdle

public int getNumIdle()

Returns the total number of instances currently idle in this pool.

Specified by:

getNumIdle in interface KeyedObjectPool

Overrides:

getNumIdle in class BaseKeyedObjectPool

Returns:

the total number of instances currently idle in this pool

getNumActive

public int getNumActive()

Returns the total number of instances current borrowed from this pool but not yet returned.

Specified by:

getNumActive in interface KeyedObjectPool

Overrides:

getNumActive in class BaseKeyedObjectPool

Returns:

the total number of instances currently borrowed from this pool

getNumActive

public int getNumActive(Object key)

Returns the number of instances currently borrowed from but not yet returned to the pool corresponding to the given key.

Specified by:

getNumActive in interface KeyedObjectPool

Overrides:

getNumActive in class BaseKeyedObjectPool

Parameters:

key - the key to query

Returns:

the number of instances corresponding to the given key currently borrowed in this pool

getNumIdle

public int getNumIdle(Object key)

Returns the number of instances corresponding to the given key currently idle in this pool.

Specified by:

getNumIdle in interface KeyedObjectPool

Overrides:

getNumIdle in class BaseKeyedObjectPool

Parameters:

key - the key to query

Returns:

the number of instances corresponding to the given key currently idle in this pool

clear

public void clear()

Clears the pool, removing all pooled instances.

Specified by:

clear in interface KeyedObjectPool

Overrides:

clear in class BaseKeyedObjectPool

clear

public void clear(Object key)

Clears the specified pool, removing all pooled instances corresponding to the given key.

Specified by:

clear in interface KeyedObjectPool

Overrides:

clear in class BaseKeyedObjectPool

Parameters:

key - the key to clear

toString

public String toString()

Overrides:

toString in class Object

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 KeyedObjectPool

Overrides:

close in class BaseKeyedObjectPool

Throws:

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

setFactory

public void setFactory(KeyedPoolableObjectFactory factory)
                throws IllegalStateException

Sets the factory the pool uses to create new instances. Trying to change the factory after a pool has been used will frequently throw an UnsupportedOperationException.

Specified by:

setFactory in interface KeyedObjectPool

Overrides:

setFactory in class BaseKeyedObjectPool

Parameters:

factory - the KeyedPoolableObjectFactory used to create new instances.

Throws:

IllegalStateException - when the factory cannot be set at this time