org.springframework.beans.factory.config
Class FieldRetrievingFactoryBean

java.lang.Object
  extended by org.springframework.beans.factory.config.FieldRetrievingFactoryBean
All Implemented Interfaces:
BeanClassLoaderAware, BeanNameAware, FactoryBean, InitializingBean

public class FieldRetrievingFactoryBean
extends Object
implements FactoryBean, BeanNameAware, BeanClassLoaderAware, InitializingBean

FactoryBean which retrieves a static or non-static field value.

Typically used for retrieving public static final constants. Usage example:

// standard definition for exposing a static field, specifying the "staticField" property
 <bean id="myField" class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean">
   <property name="staticField" value="java.sql.Connection.TRANSACTION_SERIALIZABLE"/>
 </bean>

 // convenience version that specifies a static field pattern as bean name
 <bean id="java.sql.Connection.TRANSACTION_SERIALIZABLE"
       class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean"/>

If you are using Spring 2.0, you can also use the following style of configuration for public static fields.

<util:constant static-field="java.sql.Connection.TRANSACTION_SERIALIZABLE"/>

Since:
1.1
Author:
Juergen Hoeller
See Also:
setStaticField(java.lang.String)

Constructor Summary
FieldRetrievingFactoryBean()
           
 
Method Summary
 void afterPropertiesSet()
          Invoked by a BeanFactory after it has set all bean properties supplied (and satisfied BeanFactoryAware and ApplicationContextAware).
 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.
 Class getTargetClass()
          Return the target class on which the field is defined.
 String getTargetField()
          Return the name of the field to be retrieved.
 Object getTargetObject()
          Return the target object on which the field is defined.
 boolean isSingleton()
          Is the object managed by this factory a singleton?
 void setBeanClassLoader(ClassLoader classLoader)
          Callback that supplies the bean class loader to a bean instance.
 void setBeanName(String beanName)
          The bean name of this FieldRetrievingFactoryBean will be interpreted as "staticField" pattern, if neither "targetClass" nor "targetObject" nor "targetField" have been specified.
 void setStaticField(String staticField)
          Set a fully qualified static field name to retrieve, e.g.
 void setTargetClass(Class targetClass)
          Set the target class on which the field is defined.
 void setTargetField(String targetField)
          Set the name of the field to be retrieved.
 void setTargetObject(Object targetObject)
          Set the target object on which the field is defined.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

FieldRetrievingFactoryBean

public FieldRetrievingFactoryBean()
Method Detail

setTargetClass

public void setTargetClass(Class targetClass)
Set the target class on which the field is defined. Only necessary when the target field is static; else, a target object needs to be specified anyway.

See Also:
setTargetObject(java.lang.Object), setTargetField(java.lang.String)

getTargetClass

public Class getTargetClass()
Return the target class on which the field is defined.


setTargetObject

public void setTargetObject(Object targetObject)
Set the target object on which the field is defined. Only necessary when the target field is not static; else, a target class is sufficient.

See Also:
setTargetClass(java.lang.Class), setTargetField(java.lang.String)

getTargetObject

public Object getTargetObject()
Return the target object on which the field is defined.


setTargetField

public void setTargetField(String targetField)
Set the name of the field to be retrieved. Refers to either a static field or a non-static field, depending on a target object being set.

See Also:
setTargetClass(java.lang.Class), setTargetObject(java.lang.Object)

getTargetField

public String getTargetField()
Return the name of the field to be retrieved.


setStaticField

public void setStaticField(String staticField)
Set a fully qualified static field name to retrieve, e.g. "example.MyExampleClass.MY_EXAMPLE_FIELD". Convenient alternative to specifying targetClass and targetField.

See Also:
setTargetClass(java.lang.Class), setTargetField(java.lang.String)

setBeanName

public void setBeanName(String beanName)
The bean name of this FieldRetrievingFactoryBean will be interpreted as "staticField" pattern, if neither "targetClass" nor "targetObject" nor "targetField" have been specified. This allows for concise bean definitions with just an id/name.

Specified by:
setBeanName in interface BeanNameAware
Parameters:
beanName - the name of the bean in the factory. Note that this name is the actual bean name used in the factory, which may differ from the originally specified name: in particular for inner bean names, the actual bean name might have been made unique through appending "#..." suffixes. Use the BeanFactoryUtils.originalBeanName(String) method to extract the original bean name (without suffix), if desired.

setBeanClassLoader

public void setBeanClassLoader(ClassLoader classLoader)
Description copied from interface: BeanClassLoaderAware
Callback that supplies the bean class loader to a bean instance.

Invoked after the population of normal bean properties but before an initialization callback such as InitializingBean's InitializingBean.afterPropertiesSet() method or a custom init-method.

Specified by:
setBeanClassLoader in interface BeanClassLoaderAware
Parameters:
classLoader - the owning class loader; may be null in which case a default ClassLoader must be used, for example the ClassLoader obtained via ClassUtils.getDefaultClassLoader()

afterPropertiesSet

public void afterPropertiesSet()
throws ClassNotFoundException,
NoSuchFieldException
Description copied from interface: InitializingBean
Invoked by a BeanFactory after it has set all bean properties supplied (and satisfied BeanFactoryAware and ApplicationContextAware).

This method allows the bean instance to perform initialization only possible when all bean properties have been set and to throw an exception in the event of misconfiguration.

Specified by:
afterPropertiesSet in interface InitializingBean
Throws:
ClassNotFoundException
NoSuchFieldException

getObject

public Object getObject()
throws IllegalAccessException
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
Returns:
an instance of the bean (can be null)
Throws:
IllegalAccessException
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
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
Returns:
whether the exposed object is a singleton
See Also:
FactoryBean.getObject(), SmartFactoryBean.isPrototype()


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