org.springframework.beans.factory.config
Class BeanReferenceFactoryBean

java.lang.Object
  org.springframework.beans.factory.config.BeanReferenceFactoryBean

All Implemented Interfaces:

BeanFactoryAware, FactoryBean

public class BeanReferenceFactoryBean
extends Object
implements FactoryBean, BeanFactoryAware

FactoryBean that exposes an arbitrary target bean under a different name.

Usually, the target bean will reside in a different bean definition file, using this FactoryBean to link it in and expose it under a different name. Effectively, this corresponds to an alias for the target bean.

NOTE: For XML bean definition files, an <alias> tag is available that effectively achieves the same.

A special capability of this FactoryBean is enabled through its configuration as bean definition: The "targetBeanName" can be substituted through a placeholder, in combination with Spring's PropertyPlaceholderConfigurer. Thanks to Marcus Bristav for pointing this out!

Since:

1.2

Author:

Juergen Hoeller

See Also:

setTargetBeanName(java.lang.String), PropertyPlaceholderConfigurer

Constructor Summary

BeanReferenceFactoryBean()

Method Summary

Object	getObject() Return an instance (possibly shared or independent) of the object managed by this factory.
Class	getObjectType() Return the type of object that this FactoryBean creates, or null if not known in advance.
boolean	isSingleton() Is the bean managed by this factory a singleton or a prototype?
void	setBeanFactory(BeanFactory beanFactory) Callback that supplies the owning factory to a bean instance.
void	setTargetBeanName(String targetBeanName) Set the name of the target bean.

Methods inherited from class java.lang.Object

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

Constructor Detail

BeanReferenceFactoryBean

public BeanReferenceFactoryBean()

Method Detail

setTargetBeanName

public void setTargetBeanName(String targetBeanName)

Set the name of the target bean.

This property is required. The value for this property can be substituted through a placeholder, in combination with Spring's PropertyPlaceholderConfigurer.

Parameters:

targetBeanName - the name of the target bean

See Also:

PropertyPlaceholderConfigurer

setBeanFactory

public void setBeanFactory(BeanFactory beanFactory)

Description copied from interface: BeanFactoryAware

Callback that supplies the owning factory to a bean instance.

Invoked after the population of normal bean properties but before an initialization callback such as InitializingBean.afterPropertiesSet() or a custom init-method.

Specified by:

setBeanFactory in interface BeanFactoryAware

Parameters:

beanFactory - owning BeanFactory (may not be null). The bean can immediately call methods on the factory.

See Also:

BeanInitializationException

getObject

public Object getObject()
                 throws BeansException

Description copied from interface: FactoryBean

Return an instance (possibly shared or independent) of the object managed by this factory.

As with a BeanFactory, this allows support for both the Singleton and Prototype design pattern.

If this FactoryBean is not fully initialized yet at the time of the call (for example because it is involved in a circular reference), throw a corresponding FactoryBeanNotInitializedException.

As of Spring 2.0, FactoryBeans are allowed to return null objects. The factory will consider this as normal value to be used; it will not throw a FactoryBeanNotInitializedException in this case anymore. FactoryBean implementations are encouraged to throw FactoryBeanNotInitializedException themselves now, as appropriate.

Specified by:

getObject in interface FactoryBean

Returns:

an instance of the bean (can be null)

Throws:

BeansException

See Also:

FactoryBeanNotInitializedException

getObjectType

public Class getObjectType()

Description copied from interface: FactoryBean

Return the type of object that this FactoryBean creates, or null if not known in advance.

This allows one to check for specific types of beans without instantiating objects, for example on autowiring.

In the case of implementations that are creating a singleton object, this method should try to avoid singleton creation as far as possible; it should rather estimate the type in advance. For prototypes, returning a meaningful type here is advisable too.

This method can be called before this FactoryBean has been fully initialized. It must not rely on state created during initialization; of course, it can still use such state if available.

NOTE: Autowiring will simply ignore FactoryBeans that return null here. Therefore it is highly recommended to implement this method properly, using the current state of the FactoryBean.

Specified by:

getObjectType in interface FactoryBean

Returns:

the type of object that this FactoryBean creates, or null if not known at the time of the call

See Also:

ListableBeanFactory.getBeansOfType(java.lang.Class)

isSingleton

public boolean isSingleton()

Description copied from interface: FactoryBean

Is the bean managed by this factory a singleton or a prototype? That is, will getObject() always return the same object (a reference that can be cached)?

NOTE: If a FactoryBean indicates to hold a singleton object, the object returned from getObject() might get cached by the owning BeanFactory. Hence, do not return true unless the FactoryBean always exposes the same reference.

The singleton status of the FactoryBean itself will generally be provided by the owning BeanFactory; usually, it has to be defined as singleton there.

Specified by:

isSingleton in interface FactoryBean

Returns:

if this bean is a singleton

See Also:

FactoryBean.getObject()