public class ObjectFactoryCreatingFactoryBean extends AbstractFactoryBean<ObjectFactory<Object>>
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" scope="prototype"/>
<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<MyService> myServiceFactory;
public void setMyServiceFactory(ObjectFactory<MyService> 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.
ObjectFactory,
ServiceLocatorFactoryBeanloggerOBJECT_TYPE_ATTRIBUTE| Constructor and Description |
|---|
ObjectFactoryCreatingFactoryBean() |
| Modifier and Type | Method and Description |
|---|---|
void |
afterPropertiesSet()
Eagerly create the singleton instance, if necessary.
|
protected ObjectFactory<Object> |
createInstance()
Template method that subclasses must override to construct
the object returned by this factory.
|
Class<?> |
getObjectType()
This abstract method declaration mirrors the method in the FactoryBean
interface, for a consistent offering of abstract template methods.
|
void |
setTargetBeanName(String targetBeanName)
Set the name of the target bean.
|
destroy, destroyInstance, getBeanFactory, getBeanTypeConverter, getEarlySingletonInterfaces, getObject, isSingleton, setBeanClassLoader, setBeanFactory, setSingletonpublic void setTargetBeanName(String targetBeanName)
The target does not have to be a non-singleton bean, but realistically 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 this factory approach).
public void afterPropertiesSet()
throws Exception
AbstractFactoryBeanafterPropertiesSet in interface InitializingBeanafterPropertiesSet in class AbstractFactoryBean<ObjectFactory<Object>>Exception - in the event of misconfiguration (such as failure to set an
essential property) or if initialization fails for any other reasonpublic Class<?> getObjectType()
AbstractFactoryBeangetObjectType in interface FactoryBean<ObjectFactory<Object>>getObjectType in class AbstractFactoryBean<ObjectFactory<Object>>null if not known at the time of the callFactoryBean.getObjectType()protected ObjectFactory<Object> createInstance()
AbstractFactoryBeanInvoked on initialization of this FactoryBean in case of
a singleton; else, on each AbstractFactoryBean.getObject() call.
createInstance in class AbstractFactoryBean<ObjectFactory<Object>>AbstractFactoryBean.getObject()