ObjectFactoryCreatingFactoryBean (Spring Framework API 2.1) - Spring Framework 2.1.0 API 文档英文版

org.springframework.beans.factory.config
Class ObjectFactoryCreatingFactoryBean

java.lang.Object
  org.springframework.beans.factory.config.AbstractFactoryBean
      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()           Return the type of object that this FactoryBean creates, or null if not known in advance.
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()

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.

public void setBeanFactory(BeanFactory beanFactory)

protected Object createInstance()

public void afterPropertiesSet()
                        throws Exception

public Class getObjectType()