JSF ViewParam Required +AJAX breaks page

Question

When I click the command button on the page below navigations fails. (Clicking on the button refreshes the page, removes the URL parameter and displays the required error me

Answer 1

I'll assume that the update="form" is a careless oversimplification and that you actually meant to use render="@form" and confused it with PrimeFaces or so.

Coming back to the concrete problem, that's caused by performing a non-ajax postback which triggers the processing of view parameters as well.

Either make it required on non-postback only (make sure that the bean is view scoped though),

<f:viewParam ... required="#{not facesContext.postback}" />

or pass it on postback as well

<h:commandButton ...>
    <f:param name="product" value="#{bean.product}" />
</h:commandButton>

or use OmniFaces <o:viewParam> instead if you're already using a view scoped bean. It won't process the view parameter on postbacks.

<... xmlns:o="http://omnifaces.org/ui">
...
<o:viewParam ... />