public class ServletContextAttributeFactoryBean extends Object implements FactoryBean<Object>, ServletContextAware
FactoryBean
that fetches a specific, existing ServletContext attribute.
Exposes that ServletContext attribute when used as bean reference,
effectively making it available as named Spring bean instance.
Intended to link in ServletContext attributes that exist before the startup of the Spring application context. Typically, such attributes will have been put there by third-party web frameworks. In a purely Spring-based web application, no such linking in of ServletContext attributes will be necessary.
NOTE: As of Spring 3.0, you may also use the "contextAttributes" default bean which is of type Map, and dereference it using an "#{contextAttributes.myKey}" expression to access a specific attribute by name.
WebApplicationContext.CONTEXT_ATTRIBUTES_BEAN_NAME
,
ServletContextParameterFactoryBean
OBJECT_TYPE_ATTRIBUTE
Constructor and Description |
---|
ServletContextAttributeFactoryBean() |
Modifier and Type | Method and Description |
---|---|
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 object managed by this factory a singleton? That is,
will
FactoryBean.getObject() always return the same object
(a reference that can be cached)? |
void |
setAttributeName(String attributeName)
Set the name of the ServletContext attribute to expose.
|
void |
setServletContext(ServletContext servletContext)
Set the
ServletContext that this object runs in. |
public void setAttributeName(String attributeName)
public void setServletContext(ServletContext servletContext)
ServletContextAware
ServletContext
that this object runs in.
Invoked after population of normal bean properties but before an init
callback like InitializingBean's afterPropertiesSet
or a
custom init-method. Invoked after ApplicationContextAware's
setApplicationContext
.
setServletContext
in interface ServletContextAware
servletContext
- the ServletContext object to be used by this objectInitializingBean.afterPropertiesSet()
,
ApplicationContextAware.setApplicationContext(org.springframework.context.ApplicationContext)
@Nullable public Object getObject() throws Exception
FactoryBean
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.
getObject
in interface FactoryBean<Object>
null
)Exception
- in case of creation errorsFactoryBeanNotInitializedException
public Class<?> getObjectType()
FactoryBean
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.
getObjectType
in interface FactoryBean<Object>
null
if not known at the time of the callListableBeanFactory.getBeansOfType(java.lang.Class<T>)
public boolean isSingleton()
FactoryBean
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.
isSingleton
in interface FactoryBean<Object>
FactoryBean.getObject()
,
SmartFactoryBean.isPrototype()