org.jasig.portlet.announcements.spring

Class DoubleCheckedCreator<T>

java.lang.Object

org.jasig.portlet.announcements.spring.DoubleCheckedCreator<T>

Direct Known Subclasses:

SingletonDoubleCheckedCreator

public abstract class DoubleCheckedCreator<T>
extends Object

Implementation of double-checked locking for object creation using a ReadWriteLock

Version:

$Revision$

Author:

Eric Dalquist

Field Summary

Fields

Modifier and Type	Field and Description
protected org.apache.commons.logging.Log	logger
protected Lock	readLock
protected Lock	writeLock

Constructor Summary

Constructors

Constructor and Description
DoubleCheckedCreator() Constructor for DoubleCheckedCreator.
DoubleCheckedCreator(ReadWriteLock readWriteLock) Constructor for DoubleCheckedCreator.

Method Summary

Modifier and Type	Method and Description
protected abstract T	create(Object... args) create.
T	get(Object... args) Double checking retrieval/creation of an object
protected boolean	invalid(T value, Object... args) The default impl returns true if value is null.
protected abstract T	retrieve(Object... args) retrieve.

Methods inherited from class java.lang.Object

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

Field Detail

logger

protected final org.apache.commons.logging.Log logger

readLock

protected final Lock readLock

writeLock

protected final Lock writeLock

Constructor Detail

DoubleCheckedCreator

public DoubleCheckedCreator()

Constructor for DoubleCheckedCreator.

DoubleCheckedCreator

public DoubleCheckedCreator(ReadWriteLock readWriteLock)

Constructor for DoubleCheckedCreator.

Parameters:

readWriteLock - a ReadWriteLock object.

Method Detail

create

protected abstract T create(Object... args)

create.

Parameters:

args - Arguments to use when creating the object

Returns:

A newly created object

retrieve

protected abstract T retrieve(Object... args)

retrieve.

Parameters:

args - Arguments to use when retrieving the object

Returns:

An existing object if available

invalid

protected boolean invalid(T value,
                          Object... args)

The default impl returns true if value is null.

Parameters:

value - The object to validate

args - Arguments to use when validating the object

Returns:

true if the object is invalid and should be created, false if not.

get

public final T get(Object... args)

Double checking retrieval/creation of an object

Parameters:

args - Optional arguments to pass to retrieve(Object...), create(Object...), and invalid(Object, Object...).

Returns:

A retrieved or created object.