How to create a timer counter in JSF

I want to create an online test system, so i nee开发者_开发知识库d a timer. When user start the test the timer will start counting down. But when user go to next question refresh the page the timer will still running. How can I do that any suggestion?

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You can use PrimeFaces Poll option.

The counter will always be saved on the server.

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You can also use PrimeFaces Extensions, they have timer in their API.

Example: you put start of the test into @SessionScoped bean, then calculate seconds remaining which will be used as an input to <pe:timer> element:

@SessionScoped
public class UserData {
     private Date testStart; 

     /* getters and setters for testStart */

     public int secondsRemaining() {
        //calculate seconds remaining until end of the test from this.testStart
        return secondsRemaining;
     }
}

and then your test.xhtml would contain element

Time remaining: <pe:timer format="HH:mm:ss"
                    timeout="#{userData.secondsRemaining()}"/>