org.apache.commons.pool
Interface KeyedObjectPool

All Known Implementing Classes:

BaseKeyedObjectPool, GenericKeyedObjectPool, StackKeyedObjectPool

public interface KeyedObjectPool

A "keyed" pooling interface.

A keyed pool pools instances of multiple types. Each type may be accessed using an arbitrary key.

Example of use:

 Object obj = null;
 Object key = "Key";

 try {
    obj = pool.borrowObject(key);
    //...use the object...
 } catch(Exception e) {
    //...handle any exceptions...
 } finally {
    // make sure the object is returned to the pool
    if(null != obj) {
       pool.returnObject(key,obj);
    }
 }

KeyedObjectPool implementations may choose to store at most one instance per key value, or may choose to maintain a pool of instances for each key (essentially creating a Map of pools).

Version:

$Revision: 1.6 $ $Date: 2002/05/03 17:01:06 $

Author:

Rodney Waldhoff

See Also:

KeyedPoolableObjectFactory, KeyedObjectPoolFactory, ObjectPool

Method Summary

Object	borrowObject(Object key) Obtain an instance from my pool for the specified key.
void	clear() Clears my pool, removing all pooled instances (optional operation).
void	clear(Object key) Clears the specified pool, removing all pooled instances corresponding to the given key (optional operation).
void	close() Close this pool, and free any resources associated with it.
int	getNumActive() Returns the total number of instances current borrowed from my pool but not yet returned (optional operation).
int	getNumActive(Object key) Returns the number of instances currently borrowed from but not yet returned to my pool corresponding to the given key (optional operation).
int	getNumIdle() Returns the total number of instances currently idle in my pool (optional operation).
int	getNumIdle(Object key) Returns the number of instances corresponding to the given key currently idle in my pool (optional operation).
void	returnObject(Object key, Object obj) Return an instance to my pool.
void	setFactory(KeyedPoolableObjectFactory factory) Sets the factory I use to create new instances (optional operation).

Method Detail

borrowObject

public Object borrowObject(Object key)
                    throws Exception

Obtain an instance from my pool for the specified key. By contract, clients MUST return the borrowed object using returnObject, 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.

Parameters:

key - the key used to obtain the object

Returns:

an instance from my pool.

Exception

clear

public void clear()
           throws Exception,
                  UnsupportedOperationException

Clears my pool, removing all pooled instances (optional operation). Throws UnsupportedOperationException if the pool cannot be cleared.

Throws:

UnsupportedOperationException - when this implementation doesn't support the operation

Exception

clear

public void clear(Object key)
           throws Exception,
                  UnsupportedOperationException

Clears the specified pool, removing all pooled instances corresponding to the given key (optional operation). Throws UnsupportedOperationException if the pool cannot be cleared.

Parameters:

key - the key to clear

Throws:

UnsupportedOperationException - when this implementation doesn't support the operation

Exception

close

public void close()
           throws Exception

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

Exception

getNumActive

public int getNumActive()
                 throws UnsupportedOperationException

Returns the total number of instances current borrowed from my pool but not yet returned (optional operation). Throws UnsupportedOperationException if this information is not available.

Returns:

the total number of instances currently borrowed from my pool

Throws:

UnsupportedOperationException - when this implementation doesn't support the operation

getNumActive

public int getNumActive(Object key)
                 throws UnsupportedOperationException

Returns the number of instances currently borrowed from but not yet returned to my pool corresponding to the given key (optional operation). Throws UnsupportedOperationException if this information is not available.

Parameters:

key - the key

Returns:

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

Throws:

UnsupportedOperationException - when this implementation doesn't support the operation

getNumIdle

public int getNumIdle()
               throws UnsupportedOperationException

Returns the total number of instances currently idle in my pool (optional operation). Throws UnsupportedOperationException if this information is not available.

Returns:

the total number of instances currently idle in my pool

Throws:

UnsupportedOperationException - when this implementation doesn't support the operation

getNumIdle

public int getNumIdle(Object key)
               throws UnsupportedOperationException

Returns the number of instances corresponding to the given key currently idle in my pool (optional operation). Throws UnsupportedOperationException if this information is not available.

Parameters:

key - the key

Returns:

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

Throws:

UnsupportedOperationException - when this implementation doesn't support the operation

returnObject

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

Return an instance to my 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.

Parameters:

key - the key used to obtain the object

obj - a borrowed instance to be returned.

Exception

setFactory

public void setFactory(KeyedPoolableObjectFactory factory)
                throws IllegalStateException,
                       UnsupportedOperationException

Sets the factory I use to create new instances (optional operation).

Parameters:

factory - the KeyedPoolableObjectFactory I use to create new instances.

Throws:

IllegalStateException - when the factory cannot be set at this time

UnsupportedOperationException - when this implementation doesn't support the operation