ServletContextAttributeFactoryBean (Spring Framework 3.2.1.RELEASE API)
Date: 2013-01-24

org.springframework.web.context.support

## Class ServletContextAttributeFactoryBean

- java.lang.Object
- - org.springframework.web.context.support.ServletContextAttributeFactoryBean

- All Implemented Interfaces:
    Aware, FactoryBean<Object>, ServletContextAware

      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.

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

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `ServletContextAttributeFactoryBean()`

  - ### Method Summary

    Methods
    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.

    - ### 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(String attributeName)

      Set the name of the ServletContext attribute to expose.

    - #### setServletContext

          public void setServletContext(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 Object getObject()
                           throws 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<Object>`
      Returns:
        an instance of the bean (can be `null`)
      Throws:
        `Exception` - in case of creation errors
      See Also:
        `FactoryBeanNotInitializedException`

    - #### getObjectType

          public 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<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<T>)`

    - #### 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<Object>`
      Returns:
        whether the exposed object is a singleton
      See Also:
        `FactoryBean.getObject()`, `SmartFactoryBean.isPrototype()`