org.apache.tomcat.dbcp.pool2

Class BaseObjectPool<T>

java.lang.Object

org.apache.tomcat.dbcp.pool2.BaseObject

org.apache.tomcat.dbcp.pool2.BaseObjectPool<T>

Type Parameters:

T - Type of element pooled in this pool.

All Implemented Interfaces:

ObjectPool<T>

Direct Known Subclasses:

SoftReferenceObjectPool

public abstract class BaseObjectPool<T>
extends BaseObject
implements ObjectPool<T>

A simple base implementation of ObjectPool. Optional operations are implemented to either do nothing, return a value indicating it is unsupported or throw UnsupportedOperationException.

This class is intended to be thread-safe.

Since:

2.0

Constructor Summary

Constructors

Constructor and Description
BaseObjectPool()

Method Summary

Modifier and Type	Method and Description
void	addObject() Not supported in this base implementation.
protected void	assertOpen() Throws an IllegalStateException when this pool has been closed.
abstract T	borrowObject() Obtains an instance from this pool.
void	clear() Not supported in this base implementation.
void	close() Close this pool, and free any resources associated with it.
int	getNumActive() Not supported in this base implementation.
int	getNumIdle() Not supported in this base implementation.
abstract void	invalidateObject(T obj) Invalidates an object from the pool.
boolean	isClosed() Has this pool instance been closed.
abstract void	returnObject(T obj) Return an instance to the pool.
protected void	toStringAppendFields(StringBuilder builder) Used by sub-classes to include the fields defined by the sub-class in the BaseObject.toString() output.

Methods inherited from class org.apache.tomcat.dbcp.pool2.BaseObject

toString

Methods inherited from class java.lang.Object

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

Constructor Detail

BaseObjectPool

public BaseObjectPool()

Method Detail

borrowObject

public abstract T 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 PooledObjectFactory.makeObject() or will be a previously idle object and have been activated with PooledObjectFactory.activateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>) and then validated with PooledObjectFactory.validateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>).

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:

IllegalStateException - after close has been called on this pool.

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

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

returnObject

public abstract void returnObject(T obj)
                           throws Exception

Description copied from interface: ObjectPool

Return 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.

Throws:

IllegalStateException - if an attempt is made to return an object to the pool that is in any state other than allocated (i.e. borrowed). Attempting to return an object more than once or attempting to return an object that was never borrowed from the pool will trigger this exception.

Exception - if an instance cannot be returned to the pool

invalidateObject

public abstract void invalidateObject(T obj)
                               throws Exception

Description copied from interface: ObjectPool

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.

Throws:

Exception - if the instance cannot be invalidated

getNumIdle

public int getNumIdle()

Not supported in this base implementation.

Specified by:

getNumIdle in interface ObjectPool<T>

Returns:

a negative value.

getNumActive

public int getNumActive()

Not supported in this base implementation.

Specified by:

getNumActive in interface ObjectPool<T>

Returns:

a negative value.

clear

public void clear()
           throws Exception,
                  UnsupportedOperationException

Not supported in this base implementation.

Specified by:

clear in interface ObjectPool<T>

Throws:

UnsupportedOperationException - if the pool does not implement this method

Exception - if the pool cannot be cleared

addObject

public void addObject()
               throws Exception,
                      UnsupportedOperationException

Not supported in this base implementation. Subclasses should override this behavior.

Specified by:

addObject in interface ObjectPool<T>

Throws:

UnsupportedOperationException - if the pool does not implement this method

Exception - when PooledObjectFactory.makeObject() fails.

IllegalStateException - after ObjectPool.close() has been called on this pool.

close

public void close()

Close 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.

This affects the behavior of isClosed and assertOpen.

Specified by:

close in interface ObjectPool<T>

isClosed

public final boolean isClosed()

Has this pool instance been closed.

Returns:

true when this pool has been closed.

assertOpen

protected final void assertOpen()
                         throws IllegalStateException

Throws an IllegalStateException when this pool has been closed.

Throws:

IllegalStateException - when this pool has been closed.

See Also:

isClosed()

toStringAppendFields

protected void toStringAppendFields(StringBuilder builder)

Description copied from class: BaseObject

Used by sub-classes to include the fields defined by the sub-class in the BaseObject.toString() output.

Overrides:

toStringAppendFields in class BaseObject

Parameters:

builder - Field names and values are appended to this object