binding objects initialization in JSF

Question

I have this bean in application scope.

public class User {
    private UICommand link;
    private String name;
    public User(){
        System.out.println("User.User()");
        name = "Test Link";
    }

    public UICommand getLink() {
        System.out.println("User.getLink()");
        System.out.println(link==null?"link is null":"link is not null");
        return link;
    }
    public void setLink(UICommand link) {
        System.out.println("User.setLink()");
        this.link = link;
        System.out.println("link: "+link.toString());
    }
    public void change(){
        System.out.println("User.change()");
    }
    //setter and getter for name
}

I have this jsf on jsp page.

<f:view>
<h:form>
<h:commandLink binding="#{user.link}" action="#{user.change}" value="#{user.name}"/>
</h:form>
</f:view>

I thought that the UICommand object would be reused (by sending the serialized state of the object along with the HTML output) and thus maintain the state and binding. But I get this sysoutput.

//When page loads
User.User()
User.getLink()
link is null
User.setLink()
link: javax.faces.component.html.HtmlCommandLink@14e4ce7

//when user clicks the link 
User.setLink()
link: javax.faces.component.html.HtmlCommandLink@6fcc9c
User.change()

UICommand object is different each time the user clicks the link!!! Also i believe getLink() runs only once when that object is first loaded on page but if that's the case then the page woudn't reflect the latest UICommand object!

Do you really need binding? In my humble opinion it is not a good idea to use bindings and values at the same time. — András Tóth, Feb 23 '13 at 07:48

score 2 · Accepted Answer · answered Feb 23 '13 at 08:22

2

No, each time the component tree is built/restored, you get completely new instances of UICommand. But these instances restore their state from the JSF state saving mechanism.

But you shouldn't use bindings intensively. There is almost never a good reason to do so. If you do so, always use request scope for the bean, because you will run into problems otherwise.

answered Feb 23 '13 at 08:22

chkal

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how does it maintain state if it create new instances of UICommand? – John Eipe Feb 23 '13 at 08:51
1

They implement an interface called StateHolder. The interface contains saveState() and restoreState() methods. See: http://docs.oracle.com/javaee/6/api/javax/faces/component/StateHolder.html – chkal Feb 23 '13 at 09:51

binding objects initialization in JSF

1 Answers1