如何在Primefaces Schedule

Question

我有这个PrimeFaces Schedule组件：

<h:form>
    <p:growl id="messages" showDetail="true" />
    <h:panelGrid columnClasses="value">
        <h3>Lazy Schedule</h3>
        <p:schedule value="#{visorBean.eventModel}" timeFormat="H:mm"
            draggable="true" firstHour="8" minTime="8:00" maxTime="22:00"
            resizable="true" axisFormat="H:mm" view="agendaWeek">
            <p:ajax event="eventMove" listener="#{viwerBean.onEventMove}"
                update="messages" />
            <p:ajax event="eventResize" listener="#{viwerBean.onEventResize}"
                update="messages" />
        </p:schedule>
    </h:panelGrid>
</h:form>

支持bean：

public void onEventMove(ScheduleEntryResizeEvent event) {
    String msg;
    if(isEventValid(event)) {
        msg = "Ok!";
    } else {
        msg = "Ops!";
        revertFunction(); // Undo change
    }
    FacesMessage message = new FacesMessage(FacesMessage.SEVERITY_INFO, "Event resized", msg);
    addMessage(message);
}

如何在不允许事件时撤消更改（例如，事件必须在上午8点之后开始）？