接口 FactoryBean<T>

字段详细资料

• OBJECT_TYPE_ATTRIBUTE

  static final String OBJECT_TYPE_ATTRIBUTE

  The name of an attribute that can be set on a BeanDefinition so that factory beans can signal their object type when it can't be deduced from the factory bean class.

  从以下版本开始:

  5.2

  另请参阅:

  常量字段值

方法详细资料

• getObject

  @Nullable
  T 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.

  返回:

  an instance of the bean (can be null)

  抛出:

  Exception - in case of creation errors

  另请参阅:

  FactoryBeanNotInitializedException

• getObjectType

  @Nullable
  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.

  返回:

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

  另请参阅:

  ListableBeanFactory.getBeansOfType(java.lang.Class<T>)

• isSingleton

  default 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.

  The default implementation returns true, since a FactoryBean typically manages a singleton instance.

  返回:

  whether the exposed object is a singleton

  另请参阅:

  getObject(), SmartFactoryBean.isPrototype()