Package org.apache.tomcat.dbcp.pool2.impl

Class SoftReferenceObjectPool<T>

java.lang.Object

org.apache.tomcat.dbcp.pool2.BaseObject

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

org.apache.tomcat.dbcp.pool2.impl.SoftReferenceObjectPool<T>

Type Parameters:

T - Type of element pooled in this pool.

All Implemented Interfaces:

Closeable, AutoCloseable, ObjectPool<T>

public class SoftReferenceObjectPool<T>
extends BaseObjectPool<T>

A SoftReference based ObjectPool.

This class is intended to be thread-safe.

Since:

2.0

Constructor Summary

Constructors

Constructor	Description
SoftReferenceObjectPool(PooledObjectFactory<T> factory)	Constructs a SoftReferenceObjectPool with the specified factory.

Method Summary

Modifier and Type	Method	Description
void	addObject()	Creates an object, and places it into the pool. addObject() is useful for "pre-loading" a pool with idle objects.
T	borrowObject()	Borrows an object from the pool.
void	clear()	Clears any objects sitting idle in the pool.
void	close()	Closes this pool, and frees any resources associated with it.
PooledObjectFactory<T>	getFactory()	Gets the PooledObjectFactory used by this pool to create and manage object instances.
int	getNumActive()	Gets the number of instances currently borrowed from this pool.
int	getNumIdle()	Gets an approximation not less than the of the number of idle instances in the pool.
void	invalidateObject(T obj)	Invalidates an object from the pool.
void	returnObject(T obj)	Returns an instance to the pool after successful validation and passivation.
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.BaseObjectPool

assertOpen, isClosed

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

Methods inherited from interface org.apache.tomcat.dbcp.pool2.ObjectPool

addObjects, invalidateObject

Constructor Details

SoftReferenceObjectPool

public SoftReferenceObjectPool(PooledObjectFactory<T> factory)

Constructs a SoftReferenceObjectPool with the specified factory.

Parameters:

factory - object factory to use.

Method Details

addObject

public void addObject()
               throws Exception

Creates an object, and places it into the pool. addObject() is useful for "pre-loading" a pool with idle objects.

Before being added to the pool, the newly created instance is validated and passivated. If validation fails, the new instance is destroyed. Exceptions generated by the factory makeObject or passivate are propagated to the caller. Exceptions destroying instances are silently swallowed.

Specified by:

addObject in interface ObjectPool<T>

Overrides:

addObject in class BaseObjectPool<T>

Throws:

IllegalStateException - if invoked on a closed pool

Exception - when the factory has a problem creating or passivating an object.

borrowObject

public T borrowObject()
               throws Exception

Borrows an object from the pool. If there are no idle instances available in the pool, the configured factory's PooledObjectFactory.makeObject() method is invoked to create a new instance.

All instances are activated and validated before being returned by this method. If validation fails or an exception occurs activating or validating an idle instance, the failing instance is destroyed and another instance is retrieved from the pool, validated and activated. This process continues until either the pool is empty or an instance passes validation. If the pool is empty on activation or it does not contain any valid instances, the factory's makeObject method is used to create a new instance. If the created instance either raises an exception on activation or fails validation, NoSuchElementException is thrown. Exceptions thrown by MakeObject are propagated to the caller; but other than ThreadDeath or VirtualMachineError, exceptions generated by activation, validation or destroy methods are swallowed silently.

Specified by:

borrowObject in interface ObjectPool<T>

Specified by:

borrowObject in class BaseObjectPool<T>

Returns:

a valid, activated object instance

Throws:

NoSuchElementException - if a valid object cannot be provided

IllegalStateException - if invoked on a closed pool

Exception - if an exception occurs creating a new instance

clear

public void clear()

Clears any objects sitting idle in the pool.

Specified by:

clear in interface ObjectPool<T>

Overrides:

clear in class BaseObjectPool<T>

close

public void close()

Closes this pool, and frees any resources associated with it. Invokes clear() to destroy and remove instances in the pool.

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

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface ObjectPool<T>

Overrides:

close in class BaseObjectPool<T>

getFactory

public PooledObjectFactory<T> getFactory()

Gets the PooledObjectFactory used by this pool to create and manage object instances.

Returns:

the factory

getNumActive

public int getNumActive()

Gets the number of instances currently borrowed from this pool.

Specified by:

getNumActive in interface ObjectPool<T>

Overrides:

getNumActive in class BaseObjectPool<T>

Returns:

the number of instances currently borrowed from this pool

getNumIdle

public int getNumIdle()

Gets an approximation not less than the of the number of idle instances in the pool.

Specified by:

getNumIdle in interface ObjectPool<T>

Overrides:

getNumIdle in class BaseObjectPool<T>

Returns:

estimated number of idle instances in the pool

invalidateObject

public 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>

Specified by:

invalidateObject in class BaseObjectPool<T>

Parameters:

obj - a borrowed instance to be disposed.

Throws:

Exception - if the instance cannot be invalidated

returnObject

public void returnObject(T obj)
                  throws Exception

Returns an instance to the pool after successful validation and passivation. The returning instance is destroyed if any of the following are true:

• the pool is closed
• validation fails
• passivation throws an exception

Exceptions passivating or destroying instances are silently swallowed. Exceptions validating instances are propagated to the client.

Specified by:

returnObject in interface ObjectPool<T>

Specified by:

returnObject in class BaseObjectPool<T>

Parameters:

obj - instance to return to the pool

Throws:

IllegalArgumentException - if obj is not currently part of this pool

Exception - if an instance cannot be returned to the pool

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 BaseObjectPool<T>

Parameters:

builder - Field names and values are appended to this object