Cookie简单小案例

最新推荐文章于 2025-09-13 23:06:41 发布

转载最新推荐文章于 2025-09-13 23:06:41 发布 · 98 阅读

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原文链接：https://my.oschina.net/lzwenme/blog/260832

文章标签：

#python #java

本文介绍了通过Java Servlet中的Cookie来记录并显示用户的最后访问时间，包括如何读取已有的Cookie值并将其转换为日期格式展示给用户，同时提供清除记录的方法。

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案例一

//显示用户最近的一次访问时间：lastAccessTime=98327943298
public class CookieDemo1 extends HttpServlet {

   public void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       response.setContentType("text/html;charset=UTF-8");
       PrintWriter out = response.getWriter();
       out.write("您上次访问的时间是：");
       //获取名称为lastAccessTime的cookie
       //取出它的取值，打印到页面上
       Cookie cs[] = request.getCookies();
       for(int i=0;cs!=null&&i<cs.length;i++){
           Cookie c = cs[i];
           if("lastAccessTime".equals(c.getName())){
               //我想要的
               String value = c.getValue();//时间的毫秒值
               Date time = new Date(Long.parseLong(value));
               DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
               out.write(df.format(time));
           }
       }
       out.write("<a href='"+request.getContextPath()+"/servlet/CookieDemo3'>clear</a>");
       //把最新的时间写回去
       Cookie c = new Cookie("lastAccessTime",System.currentTimeMillis()+"");
       c.setMaxAge(Integer.MAX_VALUE);//单位是秒
       c.setPath(request.getContextPath());//意味着，只要是day06下的资源
       response.addCookie(c);
   }

   public void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {

       doGet(request, response);
   }
案例二

public class CookieDemo2 extends HttpServlet {

   public void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       Cookie cs[] = request.getCookies();
       boolean found = false;
       for(int i=0;cs!=null&&i<cs.length;i++){
           Cookie c = cs[i];
           if("lastAccessTime".equals(c.getName())){
               found = true;
           }
       }
       if(found){
           System.out.println("找到了");
       }else
           System.out.println("没到了");
   }
   public void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {

       doGet(request, response);
   }
}

案例三

删除指定Cookie

public class CookieDemo3 extends HttpServlet {
   public void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       //方式一：
//       Cookie cs[] = request.getCookies();
//       for(int i=0;cs!=null&&i<cs.length;i++){
//           Cookie c = cs[i];
//           if("lastAccessTime".equals(c.getName())){
//               c.setMaxAge(0);
//               c.setPath(request.getContextPath());
//               //写回去
//               response.addCookie(c);
//           }
//       }
       //方式二：
       Cookie c = new Cookie("lastAccessTime","");
       c.setMaxAge(0);
       c.setPath(request.getContextPath());
       response.addCookie(c);
   }
   public void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       doGet(request, response);
   }
}