break; //退出 循环
            }
        }

        if (doFilter) {
            Object obj = request.getSession().getAttribute("user");//获取 session 中的值
            if (null == obj) {  //如果 session 中的值是空的话  设置 响应
                // 如果 session 中不存在登录者实体，则弹出框提示重新登录
                // 设置 request 和 response 的字符集，防止乱码
                request.setCharacterEncoding("UTF-8");
                response.setCharacterEncoding("UTF-8");
                PrintWriter out = response.getWriter();// 字符输出流
                String loginPage = "/Login/Login.do";//登录页
                StringBuilder builder = new StringBuilder();
                //javascript
                builder.append("<script type=\"text/javascript\">");
                builder.append("alert('网页过期，请重新登录！');");
                builder.append("window.top.location.href='");// 地址转到
                builder.append(contextpath);//项目 路径
                builder.append(loginPage);//  登录页
                builder.append("';");
                builder.append("</script>");
                out.print(builder.toString()); //输出
            } else {
                // 如果 session 中存在登录者实体，则继续
                filterChain.doFilter(request, response);
            }
        } else {
            // 如果不执行过滤，则继续
            filterChain.doFilter(request, response);
        }
    }
}