Can't I access session scope variable using @ManagedProperty?

Question

I know I can put/get session scope variables like this.

FacesContext.getCurrentInstance().getExternalContext()
    .getSessionMap().put(SESSION_KEY_SOME, some);

Then can't I access the value like this?

@ManagedBean
@SessionScoped
public class SomeOtherBean {

    @ManagedProperty("#{sessionScope.some}")
    private Some some;
}

The value is null.

Answer 1

@ManagedProperty runs during creation/instantiation of the @ManagedBean.

So, when the @ManagedBean is created before the #{sessionScope.some} is set for first time, then it will still remain null in the @ManagedBean. It will only work when @ManagedBean is created after the #{sessionScope.some} is set for the first time.

There are basically three ways to achieve the desired behavior.

1. Replace private Some some by externalContext.getSessionMap().get("some").

   @ManagedBean
   @SessionScoped
   public class SomeOtherBean {
   
       public void someMethod() {
           Some some = (Some) FacesContext.getCurrentInstance()
               .getExternalContext().getSessionMap().get("some");
           // ...
       }
   
   }
   

2. Replace @SessionScoped by @RequestScoped.

   @ManagedBean
   @RequestScoped
   public class SomeOtherBean {
   
       @ManagedProperty("#{sessionScope.some}")
       private Some some;
   
       // ...
   }
   

3. Replace externalContext.getSessionMap().put("some", some) by directly setting it as bean property.

   @ManagedBean
   public class SomeBean {
   
       @ManagedProperty("#{someOtherBean}")
       private SomeOtherBean someOtherBean;
   
       public void someMethod() {
           // ...
           someOtherBean.setSome(some);
       }
   
       // ...
   }
   

See also:

• How to choose the right bean scope?