作用域

1. application
   后台：ServletContext a=this.getServletContext(); a.setAttribute("name",Object);
   前台：${applicationScope.name};
2. Cookie

//使用Cookie
Cookie c=new Cookie("user",admin);
response.addCookie(c);
...
response.sendRedirect("index.jsp");

//读取Cookie
<%
Cookie[] c=request.getCookies();
String user="";
for(int i=0;i
用户名

3. JavaBean：封装数据和业务