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ObjectFactoryCreatingFactoryBean (Spring Framework API 2.0) - Spring Framework 2.0.5 API 文档英文版

The Spring Framework

org.springframework.beans.factory.config
Class ObjectFactoryCreatingFactoryBean

java.lang.Object
  extended by org.springframework.beans.factory.config.AbstractFactoryBean
      extended by org.springframework.beans.factory.config.ObjectFactoryCreatingFactoryBean
All Implemented Interfaces:
BeanFactoryAware, DisposableBean, FactoryBean, InitializingBean

public class ObjectFactoryCreatingFactoryBean
extends AbstractFactoryBean
implements BeanFactoryAware

A FactoryBean implementation that returns a value which is an ObjectFactory that in turn returns a bean sourced from a BeanFactory.

As such, this may be used to avoid having a client object directly calling BeanFactory.getBean(String) to get a (typically prototype) bean from a BeanFactory, which would be a violation of the inversion of control principle. Instead, with the use of this class, the client object can be fed an ObjectFactory instance as a property which directly returns only the one target bean (again, which is typically a prototype bean).

A sample config in an XML-based BeanFactory might look as follows:

<beans>

   <!-- Prototype bean since we have state -->
   <bean id="myService" class="a.b.c.MyService" singleton="false"/>
 
   <bean id="myServiceFactory"
            class="org.springframework.beans.factory.config.ObjectFactoryCreatingFactoryBean">
     <property name="targetBeanName"><idref local="myService"/></property>
   </bean> 
  
   <bean id="clientBean" class="a.b.c.MyClientBean">
     <property name="myServiceFactory" ref="myServiceFactory"/>
   </bean>

</beans>

The attendant MyClientBean class implementation might look something like this:

package a.b.c;
 
import org.springframework.beans.factory.ObjectFactory;
 
public class MyClientBean {
 
    private ObjectFactory myServiceFactory;
 
    public void setMyServiceFactory(ObjectFactory myServiceFactory) {
        this.myServiceFactory = myServiceFactory;
    }
 
    public void someBusinessMethod() {
        // get a 'fresh', brand new MyService instance
        MyService service = this.myServiceFactory.getObject();
        // use the service object to effect the business logic...
    }
}

An alternate approach to this application of an object creational pattern would be to use the ServiceLocatorFactoryBean to source (prototype) beans. The ServiceLocatorFactoryBean approach has the advantage of the fact that one doesn't have to depend on any Spring-specific interface such as ObjectFactory, but has the disadvantage of requiring runtime class generation. Please do consult the ServiceLocatorFactoryBean JavaDoc for a fuller discussion of this issue.

Since:
2004-05-11
Author:
Colin Sampaleanu
See Also:
ObjectFactory, ServiceLocatorFactoryBean

Field Summary
 
Fields inherited from class org.springframework.beans.factory.config.AbstractFactoryBean
logger
 
Constructor Summary
ObjectFactoryCreatingFactoryBean()
           
 
Method Summary
 void afterPropertiesSet()
          Eagerly create the singleton instance, if necessary.
protected  Object createInstance()
          Template method that subclasses must override to construct the object returned by this factory.
 Class getObjectType()
          This abstract method declaration shadows the method in the FactoryBean interface.
 void setBeanFactory(BeanFactory beanFactory)
          Callback that supplies the owning factory to a bean instance.
 void setTargetBeanName(String targetBeanName)
          Set the name of the target bean.
 
Methods inherited from class org.springframework.beans.factory.config.AbstractFactoryBean
destroy, destroyInstance, getBeanFactory, getBeanTypeConverter, getEarlySingletonInterfaces, getObject, isSingleton, setSingleton
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ObjectFactoryCreatingFactoryBean

public ObjectFactoryCreatingFactoryBean()
Method Detail

setTargetBeanName

public void setTargetBeanName(String targetBeanName)
Set the name of the target bean.

The target does not have to be a prototype bean, but realisticially always will be (because if the target bean were a singleton, then said singleton bean could simply be injected straight into the dependent object, thus obviating the need for the extra level of indirection afforded by the approach encapsulated by this class). Please note that no exception will be thrown if the supplied targetBeanName does not reference a prototype bean.


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
Overrides:
setBeanFactory in class AbstractFactoryBean
Parameters:
beanFactory - owning BeanFactory (never null). The bean can immediately call methods on the factory.
See Also:
BeanInitializationException

createInstance

protected Object createInstance()
Description copied from class: AbstractFactoryBean
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 AbstractFactoryBean.getObject() call.

Specified by:
createInstance in class AbstractFactoryBean
Returns:
the object returned by this factory
See Also:
AbstractFactoryBean.getObject()

afterPropertiesSet

public void afterPropertiesSet()
                        throws Exception
Description copied from class: AbstractFactoryBean
Eagerly create the singleton instance, if necessary.

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

getObjectType

public Class getObjectType()
Description copied from class: AbstractFactoryBean
This abstract method declaration shadows the method in the FactoryBean interface. This is necessary to make the getEarlySingletonInterfaces implementation in this class work on Sun's JDK 1.3 classic VM, which can't find the method when executing getEarlySingletonInterfaces else.

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

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