Concatenate Date objects onclick of h:commandButton - jsf

Question

I am using Primefaces 3.1.1. and very new to JSf in general.
I have two Calendar input fields on my form as such:
<p:calendar widgetVar="widgetFromDate" id="ID1" value="#{Bean.selected.From}" pattern="dd.MM.yyyy" mode="popup" showOn="button"> </p:calendar>
<p:calendar widgetVar="widgetFromTime" id="ID2" value="#{Bean.selected.Till}" pattern="HH:mm" timeOnly="true" mode="popup" showOn="button"> </p:calendar>
I have a third field which concatenates and shows the above two values on the click of h:commandButton.
For example:
The button:
<h:commandButton value="Speichern" onclick="????"></h:commandButton>
I am not really sure how one accomplishes that. Could there be a possibility to use some ajax events?
Any pointers would be greatly appreciated.
-BR

Answer 1

Just basically so:
<p:calendar ... value="#{bean.date1}" />
<p:calendar ... value="#{bean.date2}" />
<p:commandButton value="submit" action="#{bean.submit}" update="result" />
<h:outputText id="result" value="#{bean.date3}" />
with
public void submit() {
date3 = mergeSomehow(date1, date2);
}
Or if you insist in using standard JSF command button, this has the same effect:
<h:commandButton value="submit" action="#{bean.submit}">
<f:ajax execute="#form" render="result" />
</h:commandButton>
Implementation detail of merging is up to you and not in any way related to JSF/PrimeFaces. Just ask a basic java question if you stucks.
The onclick attribtue is at least insuitable for this as it provides in this particular case merely a hook to execute some JavaScript function before the form is being submitted. You're not interested in this hook.