IllegalStateException when trying to .getSessionMap() from a Session Scoped Bean

问题

I'm new to Java and JSF. I need help with an IllegalStateException. Here's the scenario:

In my current project i have this Session Scoped bean for the application menu:

public final class MenuBean implements Serializable{  
    private MenuModel model;
    private FacesContext context = FacesContext.getCurrentInstance();

    public MenuModel getModel() {
        return model;
    }

    public MenuBean() {
        updateMenu();
    }

    public void updateMenu(){
        Map session = (Map<String,Object>) context.getExternalContext().getSessionMap();
        EUser user = (EUser) session.get(UserBean.USER_SESSION_KEY);

        ...
    }

    private MethodExpression createMethodExpression(String action) {  
        ...  
    }
}

At some point of my logic, i need to update the menu, so i do this:

ExternalContext extContext = context.getExternalContext();
Map sMap = (Map<String,Object>) extContext.getSessionMap();

MenuBean menu = (MenuBean) sMap.get("menuBean");
menu.updateMenu();

The bean constructs fine, but when i try to manually update it as shown above, i get and IllegalStateException on the 1st line of the update method updateMenu()

I don't understand what's wrong, since I can get the session map with that same call whe the menu is build in the first time.

Also, using the NetBeans debugger, i can see that the instance of MenuBean is correctly recovered.

Can you guys help me?

回答1:

The FacesContext is stored in the HTTP request thread. You should absolutely not declare and assign it as an instance variable of an instance which lives longer than the HTTP request (and preferably also just not when it's already request based -it's bad design). The FacesContext instance is released and invalidated when the HTTP request finishes. In any subsequent HTTP request the instance is not valid anymore. There's means of an illegal state. That explains the IllegalStateException you're seeing.

You need to remove the following line:

private FacesContext context = FacesContext.getCurrentInstance();

And fix your code to get it only threadlocal in the method block:

Map<String, Object> sessionMap = FacesContext.getCurrentInstance().getExternalContext().getSessionMap();
// ...

You can always assign it as a variable, but that should only be kept threadlocal:

FacesContext context = FacesContext.getCurrentInstance();
Map<String, Object> sessionMap = context.getExternalContext().getSessionMap();
// ...

Unrelated to the concrete problem, using @ManagedProperty has been easier in this particular case.

public final class MenuBean implements Serializable {  

    @ManagedProperty("#{user}")
    private EUser user;

    // ...
}

JSF will then inject it for you.

来源：https://stackoverflow.com/questions/10505488/illegalstateexception-when-trying-to-getsessionmap-from-a-session-scoped-bean

标签

session

jsf

illegalstateexception

session-bean