Modifying component tree after validation failures

Question

I'm reworking a JSF web app to use JSF's validation capabilities. As it is now, the validation all occurs in various action methods, during the invoke application phase. I volunteered to do this update to separate the business processing code from the data validation code as well as take advantage of the fact that using JSF validation guarantees that the data in the model won't be updated unless the user data is valid.
So, I've run into one thing that I can't figure out how to accomplish using JSF's validation capabilities.
Here's the old form...
<!-- CITY -->
<h:inputText id="city" value="#{userDetailsBean.city}" rendered="#{userDetailsHandler.showCityInput}"/>
<h:selectOneMenu id="cityFromList" value="#{userDetailsBean.city}" rendered="#{userDetailsHandler.showCityList}">
    <f:selectItems value="#{userDetailsHandler.cityDropList}"/>
</h:selectOneMenu>
<!-- STATE -->
<h:selectOneMenu id="state" value="#{userDetailsBean.state}">
    <f:selectItem itemValue="#{null}" itemLabel=""/>
    <f:selectItems value="#{userDetailsHandler.statesList}"/>
</h:selectOneMenu>
<!-- ZIP -->
<h:inputText id="zipCode" value="#{userDetailsBean.zipCode}"/>Note that there are two components representing the city. When the form is first presented, the inputText is shown. Then, if the address doesn't validate, we present the selectOneMenu after filling userDetailsHandler.cityDropList with the appropriate city options (based on the zipcode).
So, can anybody think of a good way (from within a custom JSF validator) to set the appropriate properties in userDetailsHander in order to make the selectOneMenu render and show the proper options? Feel free to suggest a change in architecture as well. I'm not stuck on using this userDetailsHandler that was previously in use.
I figure I could always right a custom validator that takes in a bean as an attribute in the tag and the bean. On a validation error, the validator could then setup the appropriate properties in the bean. This just seams a little hacky.
By the way, the validator will probably be written to take in the names of the city, state, and zip components. I'm following the multi-component validator idea that is presented in Core Java ServerFaces, 2nd Edition. (The validator takes in the component names, which it uses to get the local values, then performs multi-component validation work.) I guess I could pass both the cityTextInput and cityListInput components into the validator, right?

Answer 1

Here's what I have so far for my validator's validate() method. Some stuff has been omitted to make this a smaller code chunk. I've attached this validator to the zip component.
public void validate(FacesContext facesCtx, UIComponent uiComponent, Object value)
               throws ValidatorException {
    // get a handle to the other components
    // city
    UIComponent cityTextComp = uiComponent.getParent().findComponent(cityTextComponent);
    EditableValueHolder cityValHolder = (EditableValueHolder) cityTextComp;
    // state
    UIComponent stateComp = uiComponent.getParent().findComponent(stateComponent);
    EditableValueHolder stateValHolder = (EditableValueHolder) stateComp;
    String city  = (String) cityValHolder.getLocalValue();
    String state = (String)stateValHolder.getLocalValue();
    String zip   = (String) value;
    System.out.println("Validating " + city + ", " + state + " " + zip);
    boolean isValid = GenericValidator.validateAddress(city, state, zip);
    if (isValid) return;
    // assume this is an invalid city for the zipcode given
    // I've removed the code for the other possibilities since it
    // doesn't pertain to my issue here
    // Setup the city list
    UIComponent cityListComp = uiComponent.getParent().findComponent(cityListComponent);
    UISelectOne cityListSelectOne = (UISelectOne) cityListComp;
    List<String> cities = GenericValidator.listCitiesForZip(zip);
    // add the appropriate items to the selectOneMenu
    for (String c: cities) {
    // WHAT DO I DO HERE?
    cityListComp.setRendered(true);
    cityTextComp.setRendered(false);
    // now signal a validation exception
    FacesMessage msg = <some faces message>;
    throw new ValidatorException(msg);
}If I can just figure out how to add the appropriate items to the h:selectOneMenu from within the validator code I presented, I'm home free, I think.