问题：在debugger中下拉框数据获取不到，主要原因session中的id为空，故想打印session中所有值看看

 HttpSession session = request.getSession();
        Enumeration enumeration = session.getAttributeNames();
        while (enumeration.hasMoreElements()){
            String name = enumeration.nextElement().toString();
            Object value = request.getSession().getAttribute(name);
            System.out.println(name+":"+value);
        }

获取session中的所有值并打印