TextItem textItem = new TextItem();
textItem.setName("reason");
textItem.setTitle("Reason");
RequiredIfValidator ifValidator = new RequiredIfValidator();
ifValidator.setExpression(new RequiredIfFunction() {
public boolean execute(FormItem formItem, Object value) {
String valueStr = (String) radioGroupItem.getValue();
return "No".equals(valueStr);
}
});