ExceptionHandler

<div class="card">
    <h:form>
        <h5 class="mt-0">AJAX</h5>
        <p:commandButton action="#{exceptionHandlerView.throwViewExpiredException}"
                         ajax="true"
                         value="Throw ViewExpiredException!" styleClass="mr-2" />
        <p:commandButton action="#{exceptionHandlerView.throwNullPointerException}"
                         ajax="true"
                         value="Throw NullPointerException!"/>
        <!-- IllegalStateException is not handled using ajaxExceptionHandlers below, so the error page is shown-->
        <p:commandButton action="#{exceptionHandlerView.throwWrappedIllegalStateException}"
                         ajax="true"
                         value="Throw IllegalStateException!" styleClass="mr-2"/>

        <h5>Non-AJAX</h5>
        <p:commandButton action="#{exceptionHandlerView.throwViewExpiredException}"
                         ajax="false"
                         value="Throw ViewExpiredException!" styleClass="mr-2"/>
        <!-- NullPointerException has no specific error-page defined in web.xml compared to ViewExpiredException -->
        <!-- https://github.com/primefaces/primefaces/blob/master/primefaces-showcase/src/main/webapp/WEB-INF/web.xml -->
        <p:commandButton action="#{exceptionHandlerView.throwNullPointerException}"
                         ajax="false"
                         value="Throw NullPointerException!"/>


        <p:ajaxExceptionHandler type="javax.faces.application.ViewExpiredException"
                                update="exceptionDialog"
                                onexception="PF('exceptionDialog').show()" />

        <p:ajaxExceptionHandler type="java.lang.NullPointerException"
                                update="exceptionDialog"
                                onexception="PF('exceptionDialog').show()"/>

        <p:dialog id="exceptionDialog" header="Exception '#{pfExceptionHandler.type}' occured!"
                  widgetVar="exceptionDialog"
                  height="500px">
            Message: #{pfExceptionHandler.message} <br/>
            StackTrace: <h:outputText value="#{pfExceptionHandler.formattedStackTrace}" escape="false"/> <br/>

            <p:button onclick="document.location.href = document.location.href;"
                      value="Reload!"
                      rendered="#{pfExceptionHandler.type == 'javax.faces.application.ViewExpiredException'}"/>
        </p:dialog>
    </h:form>
</div>