JSF selectOneMenu验证和Ajax渲染

Question

I have a validation on my selectOneMenu to prevent the user to select "None" item in the list.

<h:selectOneMenu id="selectMenu" value="#{bean.selectedValue}" required="true" requiredMessage="Please select an item">
    <f:ajax render="toRender selectMenuMessage" listener="#{bean.onSelect}"/>
    <f:selectItem itemLabel="None" noSelectionOption="true"/>
    <f:selectItems value="#{bean.items}" var="item" itemValue="#{item.id}" itemLabel="#{item.label}"/>
</h:selectOneMenu>

I have my panel below and a want to show it only when my item is not "None". So when I select "None", the message should render and the panel disappear.

<h:panelGroup id="toRender">
    <h:panelGrid rendered="#{bean.selectedValue == 0 ? false : true">
        ...
    </h:panelGrid>
</h:panelGroup>

It's working without the validation but I can't make both work.. It's like if validation prevents rendering.

Any suggestion? Thanks

Answer 1

I guess that bean.selectedValue is an Integer, so try this:

<f:selectItem itemValue="0" itemLabel="None" noSelectionOption="true"/>

---

Ah sorry, I think misunderstood your problem a little bit.
The problem here is, that if you are requiering a value for the selectOneMenu the value will not submitted if it is empty. And if the item with noSelectionOption="true" is selected, it will be handled as empty, so no value will be submitted. When you are checking against bean.selectedValue == 0 , selectedValue will never - except maybe initially - be 0, because when you select the item with value 0 it will not be submitted, as described above.
So you are right, your validation and the check for bean.selectedValue == 0 can not work together. I would recommend you to just remove the validation.
If this is no option for you, please explain me why you need it to work that way in more details.

Answer 2

I have a response, it's not the solution but it's another way to do this...

<h:selectOneMenu id="selectMenu" value="#{bean.selectedValue}">
    <f:ajax render="toRender selectMenuMessage" listener="#{bean.onSelect}"/>
    <f:selectItem itemLabel="None" noSelectionOption="true"/>
    <f:selectItems value="#{bean.items}" var="item" itemValue="#{item.id}" itemLabel="#{item.label}"/>
</h:selectOneMenu>

And in the bean

public void onSelect() {
    if(this.selectedValue != 0) {
        // Do smthg here
    } else {
        // Display error message
        UIComponent component = Outils.getFacesContext().getViewRoot().findComponent(":form:selectMenu");
        if(component != null) {   
            Outils.getFacesContext().addMessage(component.getClientId(), new FacesMessage(FacesMessage.SEVERITY_ERROR, "", "Test msg"));
        }
    }       
}

This way the validation process is not launched and the verification is done in the bean.

If someone find something better, let me know!