FactoryBean (Spring Framework) - Spring Framework 1.2.9 API 文档英文版

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org.springframework.beans.factory
Interface FactoryBean

All Known Implementing Classes:: AbstractFactoryBean, AnnotationSessionFactoryBean, BeanReferenceFactoryBean, BurlapProxyFactoryBean, CommonsLogFactoryBean, ConnectorServerFactoryBean, EhCacheFactoryBean, EhCacheManagerFactoryBean, FieldRetrievingFactoryBean, FilterDefinitionFactoryBean, FreeMarkerConfigurationFactoryBean, HessianProxyFactoryBean, HttpInvokerProxyFactoryBean, JaxRpcPortProxyFactoryBean, JndiObjectFactoryBean, JndiRmiProxyFactoryBean, JotmFactoryBean, ListFactoryBean, LocalConnectionFactoryBean, LocalJaxRpcServiceFactoryBean, LocalPersistenceManagerFactoryBean, LocalSessionFactoryBean, LocalSessionFactoryBean, LocalSessionFactoryBean, LocalStatelessSessionProxyFactoryBean, MapFactoryBean, MBeanProxyFactoryBean, MBeanServerConnectionFactoryBean, MBeanServerFactoryBean, MethodInvokingFactoryBean, MethodInvokingJobDetailFactoryBean, MethodInvokingTimerTaskFactoryBean, ObjectFactoryCreatingFactoryBean, PropertiesFactoryBean, PropertyPathFactoryBean, ProxyFactoryBean, ResourceFactoryBean, ResourceMapFactoryBean, RmiProxyFactoryBean, RmiRegistryFactoryBean, SchedulerFactoryBean, ServiceLocatorFactoryBean, ServletContextAttributeFactoryBean, ServletContextFactoryBean, ServletContextParameterFactoryBean, SetFactoryBean, SimpleRemoteStatelessSessionProxyFactoryBean, SqlMapClientFactoryBean, SqlMapFactoryBean, TimerFactoryBean, TransactionAwarePersistenceManagerFactoryProxy, TransactionAwareSessionAdapter, TransactionProxyFactoryBean, VelocityEngineFactoryBean, WebLogicJndiMBeanServerFactoryBean, WebLogicMBeanServerFactoryBean, WebLogicServerTransactionManagerFactoryBean, WebSphereTransactionManagerFactoryBean

public interface FactoryBean

Interface to be implemented by objects used within a BeanFactory that are themselves factories. If a bean implements this interface, it is used as a factory, not directly as a bean.

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 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.

This interface is heavily used within the framework, for example for the AOP ProxyFactoryBean or JndiObjectFactoryBean. It can be used for application components, but this is not common outside of infrastructure code.

Since:: 08.03.2003
Author:: Rod Johnson, Juergen Hoeller
See Also:: BeanFactory, ProxyFactoryBean, JndiObjectFactoryBean

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?

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?

Method Detail

getObject

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 method returns null, the factory will consider the FactoryBean as not fully initialized and throw a corresponding FactoryBeanNotInitializedException.

Returns:: an instance of the bean (should not be null; a null value will be considered as an indication of incomplete initialization)
Throws:: Exception - in case of creation errors
See Also:: FactoryBeanNotInitializedException

getObjectType

Class getObjectType()

Return the type of object that this FactoryBean creates, or null if not known in advance. This allows to check for specific types of beans without instantiating objects, for example on autowiring.

For a singleton, this 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:: ListableBeanFactory.getBeansOfType(java.lang.Class)

isSingleton

boolean isSingleton()

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.

Returns:: if this bean is a singleton
See Also:: getObject()