why NPE in this bean?

I have a session bean:

<managed-bean>
    <managed-bean-name>mainMenuNavigationBean</managed-bean-name>
    <managed-bean-class>com.cloud.common.jsf.core.beans.MainMenuNavigationBean</managed-bean-class>
    <managed-bean-scope>session</managed-bean-scope>
</managed-bean>

I inject this into a request bean:

<managed-bean>
    <managed-bean-name>createAccountBean</managed-bean-name>
    <managed-bean-class>com.cloud.common.jsf.account.CreateAccountBean</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>
    <managed-property>
        <property-name>mainMenuNavigationBean</property-name>
        <property-class>com.cloud.common.jsf.core.beans.MainMenuNavigationBean</property-class>
        <value>#{mainMenuNavigationBean}</value>
    </managed-property>
</managed-bean>

Now, I'm trying to use a setter in @PostConstruct of my createAccountBean but I do not understand why mainMenuNavigationBean is null here... I expect it to be autocreated if null, when accessing createAccountBean

    @PostConstruct
    public void init() {
        userLoginVo = new UserLoginVo();
        //NPE here
      开发者_运维问答  mainMenuNavigationBean.setExternalPage(true);
    }

Can you give me a hint please? I can't understand what I am doing wrong...

In order to get <managed-property> to work properly, you need to ensure that the to-be-injected bean is a public class with a (implicit) public default constructor which doesn't throw any exception upon construction.

public class MainMenuNavigationBean {

    public MainMenuNavigationBean() {
        // Can even be omitted altogether if you don't have other constructors.
    }

    // ...
}

And you need to ensure that the acceptor has a valid property and a working setter for that.

public class CreateAccountBean {

    private MainMenuNavigationBean mainMenuNavigationBean;

    public void setMainMenuNavigationBean(MainMenuNavigationBean mainMenuNavigationBean) {
        this.mainMenuNavigationBean = mainMenuNavigationBean;
    }

    // ...
}

Mind the this in the setter, if you omit that, the setter has no effect.