Proxies created using this factory bean are thread-safe singletons
and may be injected into shared objects, with transparent scoping behavior.
Proxies returned by this class implement the ScopedObject interface.
This presently allows for removing the corresponding object from the scope,
seamlessly creating a new instance in the scope on next access.
Please note that the proxies created by this factory are
class-based proxies by default. This can be customized
through switching the "proxyTargetClass" property to "false".
Is the object managed by this factory a singleton? That is,
will FactoryBean.getObject() always return the same object
(a reference that can be cached)?
Callback that supplies the owning factory to a bean instance.
Invoked after the population of normal bean properties
but before an initialization callback such as
InitializingBean.afterPropertiesSet() or a custom init-method.
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.
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.
Is the object managed by this factory a singleton? That is,
will 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.
The default implementation returns true, since a
FactoryBean typically manages a singleton instance.