Preventing multiple getter invoke in a session managed bean?

问题

i'm using jsf 2.0.2 + richfaces 3.3.3. what can i do so my getter won't be invoked multiple time ??

i have this:

@ManagedBean(name = "mybean")
@SessionScoped
public class mybean implements Serializable {        
public MyClass getMyClass() {
        if (FacesContext.getCurrentInstance().getRenderResponse()) {
            myClass = get_it_from_database();
        }
        return myClass;
    }

i also used this:

@ManagedBean(name = "mybean")
@SessionScoped
public class mybean implements Serializable {        
public MyClass getMyClass() {
        if (myClass = null) {
            myClass = get_it_from_database();
        }
        return myClass;
    }

but what i wanted is to "refresh" ONCE my data whenever i refresh the page...

回答1:

You can't prevent that. That's the nature of a getter. A getter method is intented to return data (read: to provide an access point for outside), not to load data. There you normally use the bean constructor, @PostConstruct or action method for.

To solve your particular problem, redeclare the bean to be request scoped and move the line myClass = get_it_from_database(); to bean's constructor or a @PostConstruct method if it has injected dependencies. Or if you really insist in keeping it session scoped (you should prefer having two beans: one session scoped for session scoped data and one request scoped for request scoped data), then your first approach is the most reasonable.

回答2:

make a myclass property with getter setter and return that so on referesh it will be maintained and ha use also null check as mentioned in question. Have a nice day

来源：https://stackoverflow.com/questions/3387136/preventing-multiple-getter-invoke-in-a-session-managed-bean

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