private static WriteablePropertyDescriptor findDescriptor(
     Class clazz, String propertyName, Set<WriteablePropertyDescriptor> writables)
     throws ExprValidationException {
   for (WriteablePropertyDescriptor desc : writables) {
     if (desc.getPropertyName().toLowerCase().equals(propertyName.toLowerCase())) {
       return desc;
     }
   }
   return null;
 }