Primefaces DataTable cellEdit required inputText not evaluated - jsf

Question

can someone explain why following minimal example won't evaluate the required element? Or is it the "wrong" way and there is a better one I don't know.
I'm aware that my question is similiar to this question: Primefaces cellEditor required inputText. For me it seems that the solution is more of a workaround than a valid way to cope with this problem. So yeah any ideas how to deal with this?
Code:
<p:dataTable id="ruleTableID" var="rule" value="#{rC.rules}" widgetVar="rowsTable"
rows="20" editable="#{rC.editable}"
editMode="cell" paginator="true"
paginatorPosition="bottom" paginatorTemplate="{Save}"
emptyMessage="#{t['rule.empty']}">
<p:ajax event="cellEdit" update=":newRules:messages, :newRules:" />
<p:column headerText="#{t['policy.registerNumber']}">
<p:cellEditor>
<f:facet name="input">
<p:inputText styleClass="ruleInputText" value="#{rule.registerNr}" required="true" maxlength="4">
<f:validateLength minimum="4" />
<f:validateRegex pattern="([A-Z\d]{4})" />
<p:clientValidator/>
</p:inputText>
</f:facet>
<f:facet name="output">
<h:outputText value="#{rule.registerNr}" />
</f:facet>
</p:cellEditor>
</p:column>
<f:facet name="{Save}">
<p:commandButton id="saveButton" value="#{t['button.save']}" action="#{rC.saveRules}" update=":newRules" rendered="#{rC.isAllValueSet}" />
</f:facet>
</p:dataTable>

Answer 1

If you are using client side validation you have to add the attributes ajax="false" and validateClient="true" to your commandButton
You can see a example here:
http://www.primefaces.org/showcase/ui/csv/event.xhtml