ps = con.prepareStatement("select * from USERDETAILS where username=? and password=?");
 ps.setString(1, username);
 session.setAttribute("userName", username);

var name = ${userName};
var name = '<%= Session["userName"] %>';

var name = '<%= session.getAttribute("userName") %>';

var myName= '<%= Session["myName"]%>';

var name = '<%= session.getAttribute("username") %>';

Implicit object            Description
1.     pageScope        Scoped variables from page scope
2.     requestScope     Scoped variables from request scope
3.     sessionScope     Scoped variables from session scope
4.     applicationScope Scoped variables from application scope
5.     param            Request parameters as strings
6.     paramValues      Request parameters as collections of strings
7.     header           HTTP request headers as strings
8.     headerValues     HTTP request headers as collections of strings
9.     initParam        Context-initialization parameters
10.    cookie           Cookie values
11.    pageContext      The JSP PageContext object for the current page