How can I convert a JavaScript variable to a Java variable?

I need to convert a variable from JavaScript into a Java variable. I'm asking users for their e-mail ids with a Block-UI popup through Test Box. If the field is neither null nor empty, the e-mail id should be sent to a session variable so that it can be accessed anywhere in the project.

Here's my code:

function sbtEmail(){
    var email = document.getElementById("EmailId").value;
    if (email == null || email == ""){
        alert("Enter your contact Email address to continue...!");
        document.getElementById("EmailId").focus();
    } else {
        <%session.setAttribute("quoteEmail",email);%>
        window.location.href = "demo2.jsp";
    }
}

It doesn't work. What am I doing wrong?开发者_开发百科

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You can not set a variable in the session (which resides on the server alone!) directly from JavaScript. You have to pass them to your server in some kind of request, and then the server can set it in the session.

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Solved : using Ajax will solve the Problem.

  <script type="text/javascript" src="../ajax.js"></script>

     <script type="text/javascript">
    function sbtEmail(){
        var email = document.getElementById("anonymousEmailId").value;
        if (email==null||email==""){
            alert("Enter your contact Email address to continue...!");
            document.getElementById("anonymousEmailId").focus();
        }else{
            enqueue("demo1.jsp?Id="+email,ajaxReplay);
        }
    }
    function ajaxReplay(){
        window.location.href="demo.jsp";
    }
    </script>

In demo1.jsp : set value for session variable

String Email = request.getParameter("Id");
session.setAttribute("sessEmail",Email);

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