EL session attribute and managed bean access

Question

I am confused about expression language 2 bean-view communication syntax.First of all.Is it possible to have one more managed bean with same name but different scobes.if it is what about accessing them via expression language on the other hand; consider there is an attribute in session called DemoBean and there is a session Scobed managed bean called DemoBean as well, if I try to access this bean via EL like this #{DemoBean} // refers bean or attribute? they say #{sessionScobe} is the way to access session attributes but
just #{sessionattributename} is valid ? and when I put an object to the session map is it referanced or copied?

Answer 1

JSF's aim is to manage session attributes itself for you. That means you should forget about keeping/recovering session map attributes manually, because you'll be able to do it using JSF's mechanisms.

When you want to keep some info for the whole application, use @ApplicationScoped annotation into your managed bean. You can do the same for sessions, requests or concrete views, using @SessionScoped, @RequestScoped and @ViewScoped annotations.

So, if you want to store some attribute in session:

@ManagedBean
@SessionScoped
public class SessionScopedBean{

    public String sessionAttribute;

    //Getter and setter

}

You can recover/change the value of the attribute of the bean using the FacesContext:

FacesContext context = FacesContext.getCurrentInstance();
SessionScopedBean bean = (SessionScopedBean) context.getApplication()
    .evaluateExpressionGet(context, "#{sessionScopedBean}", SessionScopedBean.class);
bean.setSessionAttribute("value");

Remember JSF beans are by default named with bean's name with the first character lowercased. And remember also this bean will be null at the first hit if you don't initialize yourself. You can do it in an easy way using a PreRenderViewEvent in the bean you want to initialize and executing it for example in your login page. That ensures the bean will keep alive for the rest of the session.

Finally, that's the way you'll access your session attribute from your view:

#{sessionScopedBean.sessionAttribute}