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public interface ObjectPool
A pooling interface.
ObjectPool
defines a trivially simple pooling interface. The only
required methods are borrowObject
, returnObject
and invalidateObject
.
Example of use:
Object obj =null
;try
{ obj = pool.borrowObject();//...use the object...
}catch
(Exception e) {// invalidate the object
pool.invalidateObject(obj);// do not return the object to the pool twice
obj =null
; }finally
{// make sure the object is returned to the pool
if
(null
!= obj) { pool.returnObject(obj); } }
See BaseObjectPool
for a simple base implementation.
PoolableObjectFactory
,
ObjectPoolFactory
,
KeyedObjectPool
,
BaseObjectPool
Method Summary | |
---|---|
void |
addObject()
Create an object using the factory or other
implementation dependent mechanism, passivate it, and then place it in the idle object pool. |
Object |
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(Object obj)
Invalidates an object from the pool. |
void |
returnObject(Object obj)
Return an instance to the pool. |
void |
setFactory(PoolableObjectFactory factory)
Sets the factory this pool uses
to create new instances (optional operation). |
Method Detail |
---|
Object borrowObject() throws Exception, NoSuchElementException, IllegalStateException
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
.
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.void returnObject(Object obj) throws Exception
obj
must have been obtained
using borrowObject
or a related method as defined in an implementation
or sub-interface.
obj
- a borrowed
instance to be returned.
Exception
void invalidateObject(Object obj) throws Exception
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.
obj
- a borrowed
instance to be disposed.
Exception
void addObject() throws Exception, IllegalStateException, UnsupportedOperationException
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).
Exception
- when PoolableObjectFactory.makeObject()
fails.
IllegalStateException
- after close()
has been called on this pool.
UnsupportedOperationException
- when this pool cannot add new idle objects.int getNumIdle() throws UnsupportedOperationException
borrowed
without creating any new instances.
Returns a negative value if this information is not available.
UnsupportedOperationException
- deprecated: if this implementation does not support the operationint getNumActive() throws UnsupportedOperationException
UnsupportedOperationException
- deprecated: if this implementation does not support the operationvoid clear() throws Exception, UnsupportedOperationException
destroyed
.
UnsupportedOperationException
- if this implementation does not support the operation
Exception
void close() throws Exception
Calling addObject()
or borrowObject()
after invoking
this method on a pool will cause them to throw an
IllegalStateException
.
Exception
- deprecated: implementations should silently fail if not all resources can be freed.void setFactory(PoolableObjectFactory factory) throws IllegalStateException, UnsupportedOperationException
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.
factory
- the PoolableObjectFactory
used to create new instances.
IllegalStateException
- when the factory cannot be set at this time
UnsupportedOperationException
- if this implementation does not support the operation
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