org.apache.commons.collections
Class FactoryUtils

java.lang.Object
  org.apache.commons.collections.FactoryUtils

public class FactoryUtils
extends java.lang.Object

FactoryUtils provides reference implementations and utilities for the Factory functor interface. The supplied factories are:

• Prototype - clones a specified object
• Reflection - creates objects using reflection
• Constant - always returns the same object
• Null - always returns null
• Exception - always throws an exception

All the supplied factories are Serializable.

Since:

Commons Collections 3.0

Version:

$Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

Stephen Colebourne

Constructor Summary

FactoryUtils()
This class is not normally instantiated.

Method Summary

static Factory	constantFactory(java.lang.Object constantToReturn) Creates a Factory that will return the same object each time the factory is used.
static Factory	exceptionFactory() Gets a Factory that always throws an exception.
static Factory	instantiateFactory(java.lang.Class classToInstantiate) Creates a Factory that can create objects of a specific type using a no-args constructor.
static Factory	instantiateFactory(java.lang.Class classToInstantiate, java.lang.Class[] paramTypes, java.lang.Object[] args) Creates a Factory that can create objects of a specific type using the arguments specified to this method.
static Factory	nullFactory() Gets a Factory that will return null each time the factory is used.
static Factory	prototypeFactory(java.lang.Object prototype) Creates a Factory that will return a clone of the same prototype object each time the factory is used.

Methods inherited from class java.lang.Object

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

Constructor Detail

FactoryUtils

public FactoryUtils()

This class is not normally instantiated.

Method Detail

exceptionFactory

public static Factory exceptionFactory()

Gets a Factory that always throws an exception. This could be useful during testing as a placeholder.

Returns:

the factory

See Also:

ExceptionFactory

nullFactory

public static Factory nullFactory()

Gets a Factory that will return null each time the factory is used. This could be useful during testing as a placeholder.

Returns:

the factory

See Also:

ConstantFactory

constantFactory

public static Factory constantFactory(java.lang.Object constantToReturn)

Creates a Factory that will return the same object each time the factory is used. No check is made that the object is immutable. In general, only immutable objects should use the constant factory. Mutable objects should use the prototype factory.

Parameters:

constantToReturn - the constant object to return each time in the factory

Returns:

the constant factory.

See Also:

ConstantFactory

prototypeFactory

public static Factory prototypeFactory(java.lang.Object prototype)

Creates a Factory that will return a clone of the same prototype object each time the factory is used. The prototype will be cloned using one of these techniques (in order):

• public clone method
• public copy constructor
• serialization clone

  Parameters:

  prototype - the object to clone each time in the factory

  Returns:

  the prototype factory

  Throws:

  java.lang.IllegalArgumentException - if the prototype is null

  java.lang.IllegalArgumentException - if the prototype cannot be cloned

  See Also:

  PrototypeFactory

instantiateFactory

public static Factory instantiateFactory(java.lang.Class classToInstantiate)

Creates a Factory that can create objects of a specific type using a no-args constructor.

Parameters:

classToInstantiate - the Class to instantiate each time in the factory

Returns:

the reflection factory

Throws:

java.lang.IllegalArgumentException - if the classToInstantiate is null

See Also:

InstantiateFactory

instantiateFactory

public static Factory instantiateFactory(java.lang.Class classToInstantiate,
                                         java.lang.Class[] paramTypes,
                                         java.lang.Object[] args)

Creates a Factory that can create objects of a specific type using the arguments specified to this method.

Parameters:

classToInstantiate - the Class to instantiate each time in the factory

paramTypes - parameter types for the constructor, can be null

args - the arguments to pass to the constructor, can be null

Returns:

the reflection factory

Throws:

java.lang.IllegalArgumentException - if the classToInstantiate is null

java.lang.IllegalArgumentException - if the paramTypes and args don't match

java.lang.IllegalArgumentException - if the constructor doesn't exist

See Also:

InstantiateFactory