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java.lang.Object org.springframework.beans.factory.config.BeanReferenceFactoryBean
public class BeanReferenceFactoryBean
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!
setTargetBeanName(java.lang.String)
,
PropertyPlaceholderConfigurer
Constructor Summary | |
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BeanReferenceFactoryBean()
|
Method Summary | |
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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 |
isPrototype()
Is the object managed by this factory a prototype? |
boolean |
isSingleton()
Is the object managed by this factory a singleton? |
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 |
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public BeanReferenceFactoryBean()
Method Detail |
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public void setTargetBeanName(String targetBeanName)
This property is required. The value for this property can be substituted through a placeholder, in combination with Spring's PropertyPlaceholderConfigurer.
targetBeanName
- the name of the target beanPropertyPlaceholderConfigurer
public void setBeanFactory(BeanFactory beanFactory)
BeanFactoryAware
Invoked after the population of normal bean properties
but before an initialization callback such as
InitializingBean.afterPropertiesSet()
or a custom init-method.
setBeanFactory
in interface BeanFactoryAware
beanFactory
- owning BeanFactory (never null
).
The bean can immediately call methods on the factory.BeanInitializationException
public Object getObject() throws BeansException
FactoryBean
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.
getObject
in interface FactoryBean
null
)
BeansException
FactoryBeanNotInitializedException
public Class getObjectType()
FactoryBean
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.
getObjectType
in interface FactoryBean
null
if not known at the time of the callListableBeanFactory.getBeansOfType(java.lang.Class)
public boolean isSingleton()
FactoryBean
FactoryBean.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.
NOTE: This method returning false
does not
necessarily indicate that returned objects are independent instances.
An implementation of the extended SmartFactoryBean
interface
may explicitly indicate independent instances through its
SmartFactoryBean.isPrototype()
method. Plain FactoryBean
implementations which do not implement this extended interface are
simply assumed to always return independent instances if the
isSingleton()
implementation returns false
.
isSingleton
in interface FactoryBean
FactoryBean.getObject()
,
SmartFactoryBean.isPrototype()
public boolean isPrototype()
SmartFactoryBean
FactoryBean.getObject()
always return an independent instance?
The prototype status of the FactoryBean itself will generally
be provided by the owning BeanFactory
; usually, it has to be
defined as singleton there.
This method is supposed to strictly check for independent instances;
it should not return true
for scoped objects or other
kinds of non-singleton, non-independent objects. For this reason,
this is not simply the inverted form of FactoryBean.isSingleton()
.
isPrototype
in interface SmartFactoryBean
FactoryBean.getObject()
,
FactoryBean.isSingleton()
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