Class PoolUtils.SynchronizedObjectPool<T>

java.lang.Object

org.datanucleus.store.rdbms.datasource.dbcp2.pool2.PoolUtils.SynchronizedObjectPool<T>

Type Parameters:

T - type of objects in the pool

All Implemented Interfaces:

Closeable, AutoCloseable, ObjectPool<T>

Enclosing class:

PoolUtils

private static final class PoolUtils.SynchronizedObjectPool<T>
extends Object
implements ObjectPool<T>

A synchronized (thread-safe) ObjectPool backed by the specified ObjectPool.

Note: This should not be used on pool implementations that already provide proper synchronization such as the pools provided in the Commons Pool library. Wrapping a pool that waits for poolable objects to be returned before allowing another one to be borrowed with another layer of synchronization will cause liveliness issues or a deadlock.

Since:

2.0

Field Summary

Fields

Modifier and Type	Field	Description
private final ObjectPool<T>	pool	the underlying object pool
private final ReentrantReadWriteLock	readWriteLock	Object whose monitor is used to synchronize methods on the wrapped pool.

Constructor Summary

Constructors

Constructor	Description
SynchronizedObjectPool(ObjectPool<T> pool)	Creates a new SynchronizedObjectPool wrapping the given pool.

Method Summary

Modifier and Type	Method	Description
void	addObject()	Creates an object using the factory or other implementation dependent mechanism, passivate it, and then place it in the idle object pool.
T	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()	Closes this pool, and free any resources associated with it.
int	getNumActive()	Returns the number of instances currently borrowed from this pool.
int	getNumIdle()	Returns the number of instances currently idle in this pool.
void	invalidateObject(T obj)	Invalidates an object from the pool.
void	returnObject(T obj)	Returns an instance to the pool.
String	toString()

Methods inherited from class Object

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

Methods inherited from interface ObjectPool

addObjects

Field Details

readWriteLock

private final ReentrantReadWriteLock readWriteLock

Object whose monitor is used to synchronize methods on the wrapped pool.

pool

private final ObjectPool<T> pool

the underlying object pool

Constructor Details

SynchronizedObjectPool

SynchronizedObjectPool(ObjectPool<T> pool)
                throws IllegalArgumentException

Creates a new SynchronizedObjectPool wrapping the given pool.

Parameters:

pool - the ObjectPool to be "wrapped" in a synchronized ObjectPool.

Throws:

IllegalArgumentException - if the pool is null

Method Details

borrowObject

public T borrowObject()
               throws Exception,
NoSuchElementException,
IllegalStateException

Obtains an instance from this pool.

Instances returned from this method will have been either newly created with PooledObjectFactory.makeObject() or will be a previously idle object and have been activated with PooledObjectFactory.activateObject(PooledObject) and then validated with PooledObjectFactory.validateObject(PooledObject).

By contract, clients must return the borrowed instance using ObjectPool.returnObject(T), ObjectPool.invalidateObject(T), 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).

Specified by:

borrowObject in interface ObjectPool<T>

Returns:

an instance from this pool.

Throws:

Exception - when PooledObjectFactory.makeObject() throws an exception.

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

IllegalStateException - after close has been called on this pool.

returnObject

public void returnObject(T obj)

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

Specified by:

returnObject in interface ObjectPool<T>

Parameters:

obj - a borrowed instance to be returned.

invalidateObject

public void invalidateObject(T obj)

Invalidates an object from the pool.

By contract, obj must have been obtained using ObjectPool.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<T>

Parameters:

obj - a borrowed instance to be disposed.

addObject

public void addObject()
               throws Exception,
IllegalStateException,
UnsupportedOperationException

Creates an object using the 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).

Specified by:

addObject in interface ObjectPool<T>

Throws:

Exception - when PooledObjectFactory.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 the number of instances currently idle in this pool. This may be considered an approximation of the number of objects that can be borrowed without creating any new instances. Returns a negative value if this information is not available.

Specified by:

getNumIdle in interface ObjectPool<T>

Returns:

the number of instances currently idle in this pool.

getNumActive

public int getNumActive()

Returns the number of instances currently borrowed from this pool. Returns a negative value if this information is not available.

Specified by:

getNumActive in interface ObjectPool<T>

Returns:

the number of instances currently borrowed from this pool.

clear

public void clear()
           throws Exception,
UnsupportedOperationException

Clears any objects sitting idle in the pool, releasing any associated resources (optional operation). Idle objects cleared must be PooledObjectFactory.destroyObject(PooledObject).

Specified by:

clear in interface ObjectPool<T>

Throws:

Exception - if the pool cannot be cleared

UnsupportedOperationException - if this implementation does not support the operation

close

public void close()

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

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

Implementations should silently fail if not all resources can be freed.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface ObjectPool<T>

toString

public String toString()

Overrides:

toString in class Object