JSP page yes/no dialog box

I have three fields on JSP Update page userid, name and ssn.. I would like to have simple dialog box saying "You already have ssn, are you 开发者_如何学Csure you want to modify it?" depending on the user's yes or no response than it performs the task? Is there a way I can add something on my java code to make this happen.. any help would be great.. thank you..

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You should use java script for this.

<script type="text/javascript">
    var response = confirm ("You already have ssn, are you sure you want to modify it?")
    if (response){
      //do yes task
    }else{
     //do no task
    }
</script>