JavaScript Validation in Struts for Drop Down List

Hi All,
I am using client side javascript validation using struts in my struts project. I have a form that contains Name, age, address, country, state fields. I have done validation for name age and address but country and state are drop down list and validation for these is not available in validation-rules.xml. All I need to is to show a alert while submitting the form if user does not choose a country and In Country drop down box, "select a country" is appearing. How to write my own validation and where? Thanks in advance.

You can write your own validation rules in any class, but I think you should just use the validwhen rule. Just put validwhen in the depends list and set variable called test = (*this* != "Select Country...") or make the field required and put value of Select Country option to empty string.