jsf-2 - selectOneMenu からの ajax 呼び出しで inputtext フィールドをレンダリングする

Question

h:selectOneMenu から選択を変更すると、h:inputtext で出力が正しくレンダリングされます。何も選択しないと問題が発生します

<h:selectOneMenu id="country_id" value="#{countryBean.countryCode}" >
                <f:validator for="country_id" validatorId="countryNameValidator"/>
                <f:selectItem itemLabel="Select Country" itemValue=" "/>
                <f:selectItems value="#{countryBean.countryList}" var="countryDTO" itemLabel="#{countryDTO.countryName}(#{countryDTO.countryCode})" itemValue="#{countryDTO.countryCode}"/>
                <f:ajax event="change" render="countryCodeValue" execute="@this" listener="#{countryBean.setCountryCodeData}"></f:ajax>
            </h:selectOneMenu>
<h:inputText disabled="true" value="#{countryBean.countryCode}" id="countryCodeValue" required="true" >
                            </h:inputText>

customCountryNameValidator.java

package com.mcd.webex.custom.validation;
import javax.faces.application.FacesMessage;
import javax.faces.component.UIComponent;
import javax.faces.component.UIInput;
import javax.faces.context.FacesContext;
import javax.faces.validator.FacesValidator;
import javax.faces.validator.Validator;
import javax.faces.validator.ValidatorException;

@FacesValidator(value="countryNameValidator")
public class CustomCountryValidator implements Validator{
    @SuppressWarnings("unused")
    public void validate(FacesContext fContext, UIComponent uiComponent, Object value)throws ValidatorException {
    String countryCode = (String) value;
    System.out.println("from Country Validation message:"+countryCode);
    FacesContext fc = FacesContext.getCurrentInstance();
    System.out.println("Country Code length: "+countryCode.trim().length());
    if(null != countryCode && countryCode.trim().length() == 0){
        FacesMessage message = new FacesMessage("Country validation failed.","Please select country.");
        message.setSeverity(FacesMessage.SEVERITY_ERROR);
        throw new ValidatorException(message);
    }else if(null == countryCode){
        FacesMessage message = new FacesMessage("Country validation failed.","Please select country.");
        message.setSeverity(FacesMessage.SEVERITY_ERROR);
        throw new ValidatorException(message);
    }
}
}