jsf 2 - How to avoid preRenderView method call in ajax request?

Question

I need to call a method in backing bean while the page loads. I achieved it using

<f:event listener="#{managedBean.onLoad}" type="preRenderView">

But whenever an ajax request is made in the page, that method get invoked again. I don't need it in my requirement. How to avoid that method call in ajax request?

Answer 1

The preRenderView event is just invoked on every request before rendering the view. An ajax request is also a request which renders a view. So the behavior is fully expected.

You've basically 2 options:

1. Replace it by @PostConstruct method on a @ViewScoped bean.

   @ManagedBean
   @ViewScoped
   public class ManagedBean {
   
       @PostConstruct
       public void onLoad() {
           // ...
       }
   
   }
   

   This is then only invoked when the bean is constructed for the first time. A view scoped bean instance lives as long as you're interacting with the same view across postbacks, ajax or not.

   ---

2. Perform a check inside the listener method if the current request is an ajax request.

   @ManagedBean
   // Any scope.
   public class ManagedBean {
   
       public void onLoad() {
           if (FacesContext.getCurrentInstance().getPartialViewContext().isAjaxRequest()) { 
               return; // Skip ajax requests.
           }
   
           // ...
       }
   
   }
   

   Or, if you're actually interested in skipping postbacks instead of specifically ajax requests, then do so instead:

           if (FacesContext.getCurrentInstance().isPostback()) { 
               return; // Skip postback requests.
           }