1.cookie和session的区别：
session cookie
保存的位置 服务端 客户端
保存的内容 Object String
2.
String getContextPath() 虚拟路径
String getRealPath(String name)虚拟路径相对的绝对路径（虚拟路径）
index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" import="java.util.Date" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<%="当前项目的虚拟路径："+application.getContextPath()+"<br/>"%>
<%="虚拟路径的绝对路径"+application.getRealPath("/untitled_war_exploded")%>
<%! String name,pwd; %>
<% int flag=0; //在缓存中寻找用户名和密码 Cookie[] cookies=request.getCookies();
for(Cookie cookie:cookies)
{ if(cookie.getName().equals("uname"))
{ name=cookie.getValue(); flag++; }
if(cookie.getName().equals("upwd"))
{ pwd=cookie.getValue(); flag++; }
} if(flag!=2)
{ out.print("cookie fail"); }
else out.print("cookie success"); %>
<form action="register.jsp"method="post">
用户名：<input type="text" name="uname" value="<%=(name==null?"":name)%>"><br/>
密码：<input type="password" name="upwd" value="<%=(pwd==null?"":pwd)%>"><br/>
<input type="submit" value="register"><br/>
</form>
</body>
</html>
register.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <% //设置编码 request.setCharacterEncoding("utf-8"); String name=request.getParameter("uname"); String pwd=request.getParameter("upwd"); Cookie cookie=new Cookie("uname",name); Cookie cookie1=new Cookie("upwd",pwd); response.addCookie(cookie); response.addCookie(cookie1); //response.sendRedirect("success.jsp"); if(name.equals("z")&&pwd.equals("z")){ //只有登入成功，session中才会存在uname/upwd session.setAttribute("uname",name); session.setAttribute("upwd",pwd); session.setMaxInactiveInterval(60*30); //response.sendRedirect("success.jsp"); out.print("sessionId "+session.getId()); Cookie cookie2=new Cookie("uname",name);//cookie服务端产生 response.addCookie(cookie2); request.getRequestDispatcher("success.jsp").forward(request,response);//响应给客户端 }else response.sendRedirect("index.jsp"); %> <br/> </body> </html>
success.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>title</title> </head> <body> 登入成功！！ <% out.println("sessionId "+session.getId()); Cookie[] cookies=request.getCookies(); for(Cookie cookie:cookies){ if(cookie.getName().equals("JSESSIONID")){ out.print("JSESSIONID "+cookie.getValue()); } } //String name=request.getParameter("uname"); String name=(String)session.getAttribute("uname"); //如果用户没有登录，而是通，过地址栏访问success.jsp，则必然获取到的name值为null //如果没有登入，应该跳转登录页面 if(name!=null) {out.println("登入成功用户"+name); %> <a href="invalidate.jsp"> 注销 </a> <% } else response.sendRedirect("login.jsp"); %> </body> </html>
参考：http://www.xuehuile.com/blog/fb1da44cf8b943d5a1a09b234bd1b12d.html