PrimeFaces: conditional update on validation

Question

Is it possible to conditionally update JSF components only when validation succeeds?

I would like to be able to do something like

Answer 1

I don't think the message suggestion necessarily answers the question asked. Suppose he wants to update something OTHER than a message?

I've not tried this myself, but another approach that might work is to use remotecommand.

<p:remoteCommand id='good' update='goodUpdates'/>  
<p:remoteCommand id='bad' update='badUpdate'/>  
<p:commandButton oncomplete='if (your-test) good() else bad()'/>  

Note, this would necessitate another round-trip to the server and thus performance is a consideration.

Answer 2

The <h:message> (or PrimeFaces' counterpart <p:message>) is intented for this. Or, in your case maybe better, the <h:messages> (or <p:messages>).

public void submit() {
    // ...

    if (fail) {
        FacesContext.getCurrentInstance().addMessage(null, 
            new FacesMessage(FacesMessage.SEVERITY_ERROR, "Fail", null));
    }
}

with

<h:messages id="messages" />
<p:commandLink process="@form" action="#{bean.submit}" update="messages something" />

Note that you're as well supposed to use a normal Validator implementation to perform the validation. If it throws a ValidatorException, then the action won't be invoked anyway. Doing validation inside action method is a smell.