org.springframework.beans.factory.config
Class AbstractFactoryBean<T>

java.lang.Object
  extended by org.springframework.beans.factory.config.AbstractFactoryBean<T>
All Implemented Interfaces:
BeanClassLoaderAware, BeanFactoryAware, DisposableBean, FactoryBean<T>, InitializingBean
Direct Known Subclasses:
AbstractServiceLoaderBasedFactoryBean, ListFactoryBean, MapFactoryBean, ObjectFactoryCreatingFactoryBean, SetFactoryBean

public abstract class AbstractFactoryBean<T>
extends java.lang.Object
implements FactoryBean<T>, BeanClassLoaderAware, BeanFactoryAware, InitializingBean, DisposableBean

Simple template superclass for FactoryBean implementations that creates a singleton or a prototype object, depending on a flag.

If the "singleton" flag is true (the default), this class will create the object that it creates exactly once on initialization and subsequently return said singleton instance on all calls to the getObject() method.

Else, this class will create a new instance every time the getObject() method is invoked. Subclasses are responsible for implementing the abstract createInstance() template method to actually create the object(s) to expose.

Since:
1.0.2
Author:
Juergen Hoeller, Keith Donald
See Also:
setSingleton(boolean), createInstance()

Field Summary
protected  org.apache.commons.logging.Log logger
          Logger available to subclasses
 
Constructor Summary
AbstractFactoryBean()
           
 
Method Summary
 void afterPropertiesSet()
          Eagerly create the singleton instance, if necessary.
protected abstract  T createInstance()
          Template method that subclasses must override to construct the object returned by this factory.
 void destroy()
          Destroy the singleton instance, if any.
protected  void destroyInstance(T instance)
          Callback for destroying a singleton instance.
protected  BeanFactory getBeanFactory()
          Return the BeanFactory that this bean runs in.
protected  TypeConverter getBeanTypeConverter()
          Obtain a bean type converter from the BeanFactory that this bean runs in.
protected  java.lang.Class[] getEarlySingletonInterfaces()
          Return an array of interfaces that a singleton object exposed by this FactoryBean is supposed to implement, for use with an 'early singleton proxy' that will be exposed in case of a circular reference.
 T getObject()
          Expose the singleton instance or create a new prototype instance.
abstract  java.lang.Class<? extends T> getObjectType()
          This abstract method declaration mirrors the method in the FactoryBean interface, for a consistent offering of abstract template methods.
 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 setBeanClassLoader(java.lang.ClassLoader classLoader)
          Callback that supplies the bean class loader to a bean instance.
 void setBeanFactory(BeanFactory beanFactory)
          Callback that supplies the owning factory to a bean instance.
 void setSingleton(boolean singleton)
          Set if a singleton should be created, or a new object on each request otherwise.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

logger

protected final org.apache.commons.logging.Log logger
Logger available to subclasses

Constructor Detail

AbstractFactoryBean

public AbstractFactoryBean()
Method Detail

setSingleton

public void setSingleton(boolean singleton)
Set if a singleton should be created, or a new object on each request otherwise. Default is true (a singleton).


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

setBeanClassLoader

public void setBeanClassLoader(java.lang.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()

setBeanFactory

public void setBeanFactory(BeanFactory beanFactory)
Description copied from interface: BeanFactoryAware
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.

Specified by:
setBeanFactory in interface BeanFactoryAware
Parameters:
beanFactory - owning BeanFactory (never null). The bean can immediately call methods on the factory.
See Also:
BeanInitializationException

getBeanFactory

protected BeanFactory getBeanFactory()
Return the BeanFactory that this bean runs in.


getBeanTypeConverter

protected TypeConverter getBeanTypeConverter()
Obtain a bean type converter from the BeanFactory that this bean runs in. This is typically a fresh instance for each call, since TypeConverters are usually not thread-safe.

Falls back to a SimpleTypeConverter when not running in a BeanFactory.

See Also:
ConfigurableBeanFactory.getTypeConverter(), SimpleTypeConverter

afterPropertiesSet

public void afterPropertiesSet()
                        throws java.lang.Exception
Eagerly create the singleton instance, if necessary.

Specified by:
afterPropertiesSet in interface InitializingBean
Throws:
java.lang.Exception - in the event of misconfiguration (such as failure to set an essential property) or if initialization fails.

getObject

public final T getObject()
                  throws java.lang.Exception
Expose the singleton instance or create a new prototype instance.

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

destroy

public void destroy()
             throws java.lang.Exception
Destroy the singleton instance, if any.

Specified by:
destroy in interface DisposableBean
Throws:
java.lang.Exception - in case of shutdown errors. Exceptions will get logged but not rethrown to allow other beans to release their resources too.
See Also:
destroyInstance(Object)

getObjectType

public abstract java.lang.Class<? extends T> getObjectType()
This abstract method declaration mirrors the method in the FactoryBean interface, for a consistent offering of abstract template methods.

Specified by:
getObjectType in interface FactoryBean<T>
Returns:
the type of object that this FactoryBean creates, or null if not known at the time of the call
See Also:
FactoryBean.getObjectType()

createInstance

protected abstract T createInstance()
                             throws java.lang.Exception
Template method that subclasses must override to construct the object returned by this factory.

Invoked on initialization of this FactoryBean in case of a singleton; else, on each getObject() call.

Returns:
the object returned by this factory
Throws:
java.lang.Exception - if an exception occured during object creation
See Also:
getObject()

getEarlySingletonInterfaces

protected java.lang.Class[] getEarlySingletonInterfaces()
Return an array of interfaces that a singleton object exposed by this FactoryBean is supposed to implement, for use with an 'early singleton proxy' that will be exposed in case of a circular reference.

The default implementation returns this FactoryBean's object type, provided that it is an interface, or null else. The latter indicates that early singleton access is not supported by this FactoryBean. This will lead to a FactoryBeanNotInitializedException getting thrown.

Returns:
the interfaces to use for 'early singletons', or null to indicate a FactoryBeanNotInitializedException
See Also:
FactoryBeanNotInitializedException

destroyInstance

protected void destroyInstance(T instance)
                        throws java.lang.Exception
Callback for destroying a singleton instance. Subclasses may override this to destroy the previously created instance.

The default implementation is empty.

Parameters:
instance - the singleton instance, as returned by createInstance()
Throws:
java.lang.Exception - in case of shutdown errors
See Also:
createInstance()