Conditional re-rendering in JSF (Richfaces)

It happens that you want something to be re-rendered only if ajax-request is executed without errors. Or in other words – you want to be lazy if it possible and not perform “reRender” if you could. Just like that funny guy – he have to be lazy to be strong
For example you have a dialog which call some ajax-action and you want to re-render it only if ajaxrequest is executed without errors
if yo’ll put a plain it will always reRender the “list” – even if ajax request has errors.

<a4j:commandLink action="#{actionBean.action}" reRender="list" value="Run"
onComplete="if (!hasAjaxErrors()){closeModalPanel();}"/>

the workaround could be moving the reRendering to a separate a4j:jsFunction call and call it only when you want it

<a4j:commandLink action="#{actionBean.action}" value="Run
onComplete="if (!hasAjaxErrors()){closeModalPanel();onCompleteFunction()}"/>

<a4j:jsFunction name="onCompleteFunction" reRender="list" ajaxSingle="true"/>

pretty easy and your “list” will be reRendered only after success call to the “#{actionBean.action}”

XHTML code to inject the error-severity in the input field “requestSeverity”

    <a4j:outputPanel ajaxRendered="true" id="severityPanel">
        <h:form prependId="false" style="display:none" >
            <h:inputHidden id="requestSeverity"
value="#{facesContext.maximumSeverity.ordinal}"/>
        </h:form>
    </a4j:outputPanel>

Javascript function to check presence of errors (error-messages-severity)

function hasAjaxErrors() {
    var errorSeverityElement = document.getElementById("requestSeverity");
    if (errorSeverityElement){
        return errorSeverityElement.value >= 2;
    }
    return false;
}