JSF: Showing page while backingBean is still working - ajax

Question

maybe this title is not really precise, but here's the problem.
I'm doing some JSF project and I need a following:
When user logs on my application (ie. when he navigates to Home page), a method, which gets some money exchange rates from the internet and/or database, needs to be called. The execution of that method (page parsing, data saving etc.) lasts about 5-6 seconds. I don't want that navigation from Login to Home page lasts 5-6 seconds, i want one of these (didn't decide which one yet) to happen:
1) When user logs in, he sees Home page (immediately, not after 5-6 seconds) and is able to click and/or navigate while method is working in background.
2) When user logs in, he sees Home page (immediately), some loading sign in one part of the page and after method is executed, he sees dataTable with exchange rates.
Question is, how to do any of this?
If I put that method in HomePageBean constructor, page wont be displayed until method is executed. Maybe i can put some invisible element on Home page and call that method within some Getter, but i don't know if that's the right way to do (seems like hack) or will it actually work.
I'm using JSF 2.0 and Primefaces.
Thanks in advance

Answer 1

Use ApplicationScoped bean like in example below:
#ManagedBean(name = "exchRateBean", eager = true)
#ApplicationScoped
public class ExchRateBean {
public List<Rate> getRates(Date date) {
// cached data or DAO methods here
}
#PostConstruct
public void init() {
// Initial web-app initialization, will run once upon deploy
}
}
And here is your backing bean accessing application-scoped bean.
#RequestScoped
public class MyBean {
#ManagedProperty(value="#{exchRateBean}")
private ExchRateBean exchRateBean;
// your JSF methods
public List<Rate> getRates(Date date) {
return getExchRateBean().getRates(date);
}
// G&S
public ExchRateBean getExchRateBean() {
return exchRateBean;
}
public void setExchRateBean(ExchRateBean exchRateBean) {
this.exchRateBean = exchRateBean;
}
}