Interface FactoryBean<T>
- Type Parameters:
T
- the bean type
- All Known Subinterfaces:
SmartFactoryBean<T>
- All Known Implementing Classes:
AbstractEntityManagerFactoryBean
,AbstractFactoryBean
,AbstractServiceLoaderBasedFactoryBean
,AbstractSingletonProxyFactoryBean
,CacheProxyFactoryBean
,ConcurrentMapCacheFactoryBean
,ConnectorServerFactoryBean
,ContentNegotiationManagerFactoryBean
,ConversionServiceFactoryBean
,CronTriggerFactoryBean
,DateTimeFormatterFactoryBean
,EmbeddedDatabaseFactoryBean
,FieldRetrievingFactoryBean
,ForkJoinPoolFactoryBean
,FormattingConversionServiceFactoryBean
,FreeMarkerConfigurationFactoryBean
,GsonFactoryBean
,Jackson2ObjectMapperFactoryBean
,JCacheManagerFactoryBean
,JndiObjectFactoryBean
,JobDetailFactoryBean
,JtaTransactionManagerFactoryBean
,ListFactoryBean
,LocalConnectionFactoryBean
,LocalContainerEntityManagerFactoryBean
,LocalEntityManagerFactoryBean
,LocalSessionFactoryBean
,MapFactoryBean
,MBeanProxyFactoryBean
,MBeanServerConnectionFactoryBean
,MBeanServerFactoryBean
,MethodInvokingFactoryBean
,MethodInvokingJobDetailFactoryBean
,MethodLocatingFactoryBean
,ObjectFactoryCreatingFactoryBean
,PropertiesFactoryBean
,PropertyPathFactoryBean
,ProviderCreatingFactoryBean
,ProxyFactoryBean
,ProxyFactoryBean
,ResourceAdapterFactoryBean
,ScheduledExecutorFactoryBean
,SchedulerFactoryBean
,ScopedProxyFactoryBean
,ServiceFactoryBean
,ServiceListFactoryBean
,ServiceLoaderFactoryBean
,ServiceLocatorFactoryBean
,ServletContextAttributeFactoryBean
,ServletContextParameterFactoryBean
,ServletServerContainerFactoryBean
,SetFactoryBean
,SharedEntityManagerBean
,SimpleTriggerFactoryBean
,SortedResourcesFactoryBean
,TaskExecutorFactoryBean
,ThreadPoolExecutorFactoryBean
,TransactionProxyFactoryBean
,WebSocketContainerFactoryBean
,YamlMapFactoryBean
,YamlPropertiesFactoryBean
BeanFactory
which
are themselves factories for individual objects. If a bean implements this
interface, it is used as a factory for an object to expose, not directly as a
bean instance that will be exposed itself.
NB: A bean that implements this interface cannot be used as a normal bean.
A FactoryBean is defined in a bean style, but the object exposed for bean
references (getObject()
) is always the object that it creates.
FactoryBeans can support singletons and prototypes, and can either create
objects lazily on demand or eagerly on startup. The SmartFactoryBean
interface allows for exposing more fine-grained behavioral metadata.
This interface is heavily used within the framework itself, for example for
the AOP ProxyFactoryBean
or the
JndiObjectFactoryBean
. It can be used for
custom components as well; however, this is only common for infrastructure code.
FactoryBean
is a programmatic contract. Implementations are not
supposed to rely on annotation-driven injection or other reflective facilities.
Invocations of getObjectType()
and getObject()
may arrive early
in the bootstrap process, even ahead of any post-processor setup. If you need access
to other beans, implement BeanFactoryAware
and obtain them programmatically.
The container is only responsible for managing the lifecycle of the FactoryBean
instance, not the lifecycle of the objects created by the FactoryBean. Therefore,
a destroy method on an exposed bean object (such as Closeable.close()
)
will not be called automatically. Instead, a FactoryBean should implement
DisposableBean
and delegate any such close call to the underlying object.
Finally, FactoryBean objects participate in the containing BeanFactory's synchronization of bean creation. Thus, there is usually no need for internal synchronization other than for purposes of lazy initialization within the FactoryBean itself (or the like).
- Since:
- 08.03.2003
- Author:
- Rod Johnson, Juergen Hoeller
- See Also:
-
Field Summary
Modifier and TypeFieldDescriptionstatic final String
The name of an attribute that can beset
on aBeanDefinition
so that factory beans can signal their object type when it cannot be deduced from the factory bean class. -
Method Summary
Modifier and TypeMethodDescriptionReturn an instance (possibly shared or independent) of the object managed by this factory.Class<?>
Return the type of object that this FactoryBean creates, ornull
if not known in advance.default boolean
Is the object managed by this factory a singleton? That is, willgetObject()
always return the same object (a reference that can be cached)?
-
Field Details
-
OBJECT_TYPE_ATTRIBUTE
The name of an attribute that can beset
on aBeanDefinition
so that factory beans can signal their object type when it cannot be deduced from the factory bean class.- Since:
- 5.2
- See Also:
-
-
Method Details
-
getObject
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 patterns.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
.FactoryBeans are allowed to return
null
objects. The bean factory will consider this as a normal value to be used and will not throw aFactoryBeanNotInitializedException
in this case. However, FactoryBean implementations are encouraged to throwFactoryBeanNotInitializedException
themselves, as appropriate.- Returns:
- an instance of the bean (can be
null
) - Throws:
Exception
- in case of creation errors- See Also:
-
getObjectType
Return the type of object that this FactoryBean creates, ornull
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 create 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.- Returns:
- the type of object that this FactoryBean creates,
or
null
if not known at the time of the call - See Also:
-
isSingleton
default boolean isSingleton()Is the object managed by this factory a singleton? That is, willgetObject()
always return the same object (a reference that can be cached)?NOTE: If a FactoryBean indicates that it holds a singleton object, the object returned from
getObject()
might get cached by the owning BeanFactory. Hence, do not returntrue
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 extendedSmartFactoryBean
interface may explicitly indicate independent instances through itsSmartFactoryBean.isPrototype()
method. PlainFactoryBean
implementations which do not implement this extended interface are simply assumed to always return independent instances if theisSingleton()
implementation returnsfalse
.The default implementation returns
true
, since aFactoryBean
typically manages a singleton instance.- Returns:
- whether the exposed object is a singleton
- See Also:
-