org.springframework.beans.factory.config

Class AbstractFactoryBean<T>

java.lang.Object

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

All Implemented Interfaces:

Aware, BeanClassLoaderAware, BeanFactoryAware, DisposableBean, FactoryBean<T>, InitializingBean

Direct Known Subclasses:

AbstractServiceLoaderBasedFactoryBean, ListFactoryBean, MapFactoryBean, ObjectFactoryCreatingFactoryBean, ProviderCreatingFactoryBean, SetFactoryBean, SortedResourcesFactoryBean

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()

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private class	AbstractFactoryBean.EarlySingletonInvocationHandler Reflective InvocationHandler for lazy access to the actual singleton object.

Field Summary

Fields

Modifier and Type	Field and Description
private java.lang.ClassLoader	beanClassLoader
private BeanFactory	beanFactory
private T	earlySingletonInstance
private boolean	initialized
protected Log	logger Logger available to subclasses
private boolean	singleton
private T	singletonInstance

Constructor Summary

Constructors

Constructor and Description
AbstractFactoryBean()

Method Summary

Methods

Modifier and Type	Method and Description
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.
private T	getEarlySingletonInstance() Determine an 'eager singleton' instance, exposed in case of a circular reference.
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<?>	getObjectType() This abstract method declaration mirrors the method in the FactoryBean interface, for a consistent offering of abstract template methods.
private T	getSingletonInstance() Expose the singleton instance (for access through the 'early singleton' proxy).
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 Log logger

Logger available to subclasses

singleton

private boolean singleton

beanClassLoader

private java.lang.ClassLoader beanClassLoader

beanFactory

private BeanFactory beanFactory

initialized

private boolean initialized

singletonInstance

private T singletonInstance

earlySingletonInstance

private T earlySingletonInstance

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()

getEarlySingletonInstance

private T getEarlySingletonInstance()
                             throws java.lang.Exception

Determine an 'eager singleton' instance, exposed in case of a circular reference. Not called in a non-circular scenario.

Throws:

java.lang.Exception

getSingletonInstance

private T getSingletonInstance()
                        throws java.lang.IllegalStateException

Expose the singleton instance (for access through the 'early singleton' proxy).

Returns:

the singleton instance that this FactoryBean holds

Throws:

java.lang.IllegalStateException - if the singleton instance is not initialized

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<?> 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()