我的session已经尝试了N种方法了~还是不行

try{
    String userName=request.getParameter("username");
    String password=request.getParameter("password");
    System.out.println(userName);
    System.out.println(password);
    List<HashMap<String,Object>>list=JDBCOption.query(SQLConstant.loginQuery, userName,password);
    List rs=JDBCOption.query(SQLConstant.loginQuery, userName,password);
    if(list.size()>0)
    {
        HttpSession session=request.getSession(true);
        System.out.println("111");
        //Integer userID=(Integer)(list.get(0).get("id"));
        System.out.println("222");
        //String userName1=(String) (list.get(0).get("username"));
        System.out.println(userName);
        //request.getSession().setAttribute(Constant.USERID_MARK,userID);
        request.getSession().setAttribute(Constant.USER_NAME_MARK,userName);        
        //session.putValue(Constant.USER_NAME_MARK, userName);
        //session.setAttribute(Constant.USER_NAME_MARK, userName);
        System.out.println(Constant.USER_NAME_MARK);
        response.sendRedirect("/index.jsp");
    }

是不是输出方式不对~~

session与response.sendRedirect有关系，可以百度一下