org.springframework.beans.factory: public interface: FactoryBean

org.springframework.beans.factory
public interface: FactoryBean [javadoc | source]

All Known Implementing Classes:
JndiObjectFactoryBean, MethodInvokingTimerTaskFactoryBean, HessianProxyFactoryBean, ScheduledExecutorFactoryBean, PropertiesFactoryBean, SharedEntityManagerBean, JotmFactoryBean, HttpInvokerProxyFactoryBean, JaxWsPortProxyFactoryBean, ObjectFactoryCreatingFactoryBean, SimpleHttpServerFactoryBean, LocalStatelessSessionProxyFactoryBean, ProxyFactoryBean, AbstractEntityManagerFactoryBean, CommonsLogFactoryBean, LocalPersistenceManagerFactoryBean, EhCacheManagerFactoryBean, WebSphereTransactionManagerFactoryBean, JmsInvokerProxyFactoryBean, FieldRetrievingFactoryBean, LocalSessionFactoryBean, TransactionAwarePersistenceManagerFactoryProxy, LocalSessionFactoryBean, ConnectorServerFactoryBean, LocalContainerEntityManagerFactoryBean, TransactionAwareSessionAdapter, MapFactoryBean, AbstractSessionFactoryBean, WebLogicServerTransactionManagerFactoryBean, SetFactoryBean, ServiceFactoryBean, ScheduledExecutorFactoryBean, WebSphereMBeanServerFactoryBean, ServletContextAttributeFactoryBean, LocalJaxWsServiceFactoryBean, SqlMapClientFactoryBean, AbstractFactoryBean, FreeMarkerConfigurationFactoryBean, ServletContextParameterFactoryBean, WebLogicJndiMBeanServerFactoryBean, JndiRmiProxyFactoryBean, EhCacheFactoryBean, ResourceFactoryBean, SmartFactoryBean, SchedulerFactoryBean, BeanReferenceFactoryBean, MBeanServerFactoryBean, ResourceMapFactoryBean, MethodInvokingFactoryBean, AnnotationSessionFactoryBean, ResourceAdapterFactoryBean, FilterDefinitionFactoryBean, SqlMapFactoryBean, RmiRegistryFactoryBean, ListFactoryBean, MBeanProxyFactoryBean, TransactionProxyFactoryBean, SimpleRemoteStatelessSessionProxyFactoryBean, AbstractServiceLoaderBasedFactoryBean, LocalEntityManagerFactoryBean, RmiProxyFactoryBean, ServiceListFactoryBean, ServiceLocatorFactoryBean, MBeanServerConnectionFactoryBean, MethodInvokingJobDetailFactoryBean, BurlapProxyFactoryBean, LocalJaxRpcServiceFactoryBean, AbstractSingletonProxyFactoryBean, ServiceLoaderFactoryBean, WebLogicMBeanServerFactoryBean, LocalSessionFactoryBean, LocalConnectionFactoryBean, MethodLocatingFactoryBean, ServletContextFactoryBean, PropertyPathFactoryBean, TimerManagerFactoryBean, VelocityEngineFactoryBean, TimerFactoryBean, ScopedProxyFactoryBean, JaxRpcPortProxyFactoryBean

Interface to be implemented by objects used within a BeanFactory which are themselves factories. 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 org.springframework.aop.framework.ProxyFactoryBean or the org.springframework.jndi.JndiObjectFactoryBean . It can be used for application components as well; however, this is not common outside of infrastructure code.

NOTE: FactoryBean objects participate in the containing BeanFactory's synchronization of bean creation. There is usually no need for internal synchronization other than for purposes of lazy initialization within the FactoryBean itself (or the like).

Also see:

org.springframework.beans.factory.BeanFactory

org.springframework.aop.framework.ProxyFactoryBean

org.springframework.jndi.JndiObjectFactoryBean

author: Rod - Johnson

author: Juergen - Hoeller

since: 08.03.2003 -

Method from org.springframework.beans.factory.FactoryBean Summary:
getObject, getObjectType, isSingleton

Method from org.springframework.beans.factory.FactoryBean Detail:
public Object getObject() throws Exception 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.
public Class getObjectType() 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.
public boolean isSingleton() Is the object managed by this factory a singleton? 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. 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`.

Method from org.springframework.beans.factory.FactoryBean Detail:

 public Object getObject() throws ExceptionReturn 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.

 public Class getObjectType()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.

 public boolean isSingleton()Is the object managed by this factory a singleton? 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.
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.