Update View with Backend, won't work - primefaces

Question

Following issue, I want to update my front-end from my backing-bean.
View:
<p:layoutUnit id="center" position="center">
<p:layout>
<p:layoutUnit id="inner_north" position="north" size="100">
<h:form id="fortschrittForm">
<h:panelGrid columns="10" id="fortschritt" cellspacing="7" title="Fortschritt" cellpadding="6">
<h:outputText value="Mails heruntergeladen:"/>
<p:graphicImage library="img" name="erfolg.png"
rendered="#{managedBean.mails}" />
<h:outputText value="Pdfs wurden gelesen:"/>
<p:graphicImage library="img" name="erfolg.png"
rendered="#{managedBean.pdfs}" />
</h:panelGrid>
</h:form>
[...]
Button:
<p:commandButton value="Transition starten" actionListener="#{managedBean.prozessablauf}" update=":formTabelle:formDetail:msg anzeigeRisiko"/>
Backend:
public void prozessablauf() {
try {
emailHerunterladen();
mails = true;
RequestContext.getCurrentInstance().update("fortschrittForm:fortschritt");
} catch (Exception e) {
e.printStackTrace();
}
My problem is that
RequestContext.getCurrentInstance().update("fortschrittForm:fortschritt");
is not firing. Just when the method is completely done, all icons are shown. But I want in particular to update the fortschrittForm.
Heres the code in from firebug:
enter image description here

Answer 1

My problem is that
RequestContext.getCurrentInstance().update("fortschrittForm:fortschritt");
is not firing.
You misunderstand the behavior of RequestContext#update method. It does not trigger a seperate response. It just provides a simple way to set which components to update within the current request at runtime instead of hardcoding it via the update attribute in the markup.
Just when the method is completely done, all icons are shown.
This is the normal behavior.
Every change to the view on the client side has to be made with a request from the client side. This is how it works (unless you are using sockets or something like this). So to reflect updates from a long running or composite process on the server side, you have to poll for updates from the client as long as the process is running.
E.g. <p:poll /> is a very good candidate to go with and i would try something like this:
When requesting the start of the process on the client side, also start <p:poll /> with update attribute set to the target part of the view.
While the process is running on the server side, update the model values associated with the target part of the view on the client side respectivley.
When process ends on the server side, request a final update of the target part of the view and stop polling on the client side.
In addition I just found something interesting, which may be an option for you also. Have a look at PrimeFaces Push