问放入SQL预处理语句中的javascript变量(java)

EN

        var e = document.getElementById("categoryName");
        var selectItem = e.options[e.selectedIndex].text;

var theData = [ // Start of JavaScript data object

        <%
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/pyramid", "root", "test");
            PreparedStatement ps = con.prepareStatement("SELECT timeStamp, value FROM status WHERE idCategory = (SELECT idCategory FROM  category WHERE name =' " SELECTITEMVARIABLE " ')");