Getting backing bean value with Javascript

Question

JSF 2.0, Mojarra 2.0.1, PrimeFaces 3.4.1

There are similar questions but I need sth. else; javascript function has to wait for the backing bean method, whic

Answer 1

JSF/EL and HTML/JS doesn't run in sync. Instead, JSF/EL run in webserver and produces HTML/JS which in turn runs in webbrowser. Open page in browser, rightclick and View Source. You see, there's no single line of JSF/EL. It's one and all HTML/JS. In place of your JS function, you'll see:

function afterLoad() {    
    alert("0");
}

Exactly this JS function get invoked on complete of your command button action. So the result is fully expected.

Basically, you want to let JSF re-render that piece of JS.

<p:commandLink action="#{statusBean.getStatuses}" update="afterLoad" oncomplete="afterLoad()"/>
<h:panelGroup id="afterLoad">
    <h:outputScript>
        function afterLoad() {    
            alert("#{statusBean.size}");
        }
    </h:outputScript>
</h:panelGroup>

Depending on the concrete functional requirement, which you didn't tell anything about, there may be more elegant ways. For example, RequestContext#execute(), <o:onloadScript>, etc.

Answer 2

EL in your JavaScript is calculated when page is rendered and you can update its container (if it is in some JSF component), but I would suggest another approach.

As you are making AJAX request, you can add callback parameter in getStatuses() method. You can use Primefaces's RequestContext utility method addCallBackParam() for this:

public void getStatuses() {
    this.panelList = fillList();
    this.size = panelList.size();
    RequestContext.getCurrentInstance().addCallBackParam("size", this.size);
}

and you can use this parameter in xhtml:

<p:commandLink action="#{statusBean.getStatuses}" oncomplete="afterLoad(xhr, status, args)"/>

<script type="text/javascript">
  function afterLoad(xhr, status, args) {    
    alert(args.size);
  }
</script>