Are there going to be two instances for a bean if I write @managed bean annotation and define same in faces-config.xml

问题

In my application in some places we are using @ManagedBean annoation for Person bean and for the same Person bean we defining in the faces-confing.xml like below at the same time.

@ManagedBean("name=person")
 @SessionScoped
 Public class Person{


}

faces-config.xml

<managed-bean>
     <managed-bean-name>person</managed-bean-name>
     <managed-bean-class>com.test.sample.Person</managed-bean-class>
     <managed-bean-scope>session</managed-bean-scope>
</managed-bean>

my question is does this approach create two instances for the Person bean or it does matter if I do this? Does this have any effect on performance of my application If I do this for every Bean in my application?

回答1:

There's a priority defined for this case. @ManagedBean annotation avoids having to configure an entry in faces-config.xml but, if you have both, the <managed-bean> entry overrides the annotation.

In your case, there'll be only one instance configured like your faces-config.xml entry. In your case, both approaches are configured the same way but, should you change your faces-config.xml entry to something like

<managed-bean>
     <managed-bean-name>personBean</managed-bean-name>
     <managed-bean-class>com.test.sample.Person</managed-bean-class>
     <managed-bean-scope>session</managed-bean-scope>
</managed-bean>

Your bean will be registered under personBean rather than person (which is the name defined by the annotation).

来源：https://stackoverflow.com/questions/12750771/are-there-going-to-be-two-instances-for-a-bean-if-i-write-managed-bean-annotati