Spring Framework

org.springframework.web.context.support
Class ServletContextAttributeFactoryBean

java.lang.Object
  extended by org.springframework.web.context.support.ServletContextAttributeFactoryBean
All Implemented Interfaces:
Aware, FactoryBean<java.lang.Object>, ServletContextAware

public class ServletContextAttributeFactoryBean
extends java.lang.Object
implements FactoryBean<java.lang.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.

Since:
1.1.4
Author:
Juergen Hoeller
See Also:
WebApplicationContext.CONTEXT_ATTRIBUTES_BEAN_NAME, ServletContextParameterFactoryBean

Constructor Summary
ServletContextAttributeFactoryBean()
           
 
Method Summary
 java.lang.Object getObject()
          Return an instance (possibly shared or independent) of the object managed by this factory.
 java.lang.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(java.lang.String attributeName)
          Set the name of the ServletContext attribute to expose.
 void setServletContext(javax.servlet.ServletContext servletContext)
          Set the ServletContext that this object runs in.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ServletContextAttributeFactoryBean

public ServletContextAttributeFactoryBean()
Method Detail

setAttributeName

public void setAttributeName(java.lang.String attributeName)
Set the name of the ServletContext attribute to expose.


setServletContext

public void setServletContext(javax.servlet.ServletContext servletContext)
Description copied from interface: ServletContextAware
Set the 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.

Specified by:
setServletContext in interface ServletContextAware
Parameters:
servletContext - ServletContext object to be used by this object
See Also:
InitializingBean.afterPropertiesSet(), ApplicationContextAware.setApplicationContext(org.springframework.context.ApplicationContext)

getObject

public java.lang.Object getObject()
                           throws java.lang.Exception
Description copied from interface: FactoryBean
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.

Specified by:
getObject in interface FactoryBean<java.lang.Object>
Returns:
an instance of the bean (can be null)
Throws:
java.lang.Exception - in case of creation errors
See Also:
FactoryBeanNotInitializedException

getObjectType

public java.lang.Class<?> getObjectType()
Description copied from interface: FactoryBean
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.

Specified by:
getObjectType in interface FactoryBean<java.lang.Object>
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

public boolean isSingleton()
Description copied from interface: 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.

Specified by:
isSingleton in interface FactoryBean<java.lang.Object>
Returns:
whether the exposed object is a singleton
See Also:
FactoryBean.getObject(), SmartFactoryBean.isPrototype()

Spring Framework