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  • Java实现 Cookie的生成与读取

    今天学习的时候发现Cookie挺有意思的,就自己网上找点例子,自己敲点代码熟练下,现在就记录下来,分享一下。

    什么是cookie??

    Cookie 是一小段文本信息,伴随着用户请求和页面在 Web 服务器和浏览器之间传递。Cookie 包含每次用户访问站点时 Web 应用程序都可以读取的信息。因为HTTP协议是无状态的,对于一个浏览器发出的多次请求,WEB服务器无法区分 是不是来源于同一个浏览器。所以,需要额外的数据用于维护会话。 Cookie 正是这样的一段随HTTP请求一起被传递的额外数据。可见它是用于维持服务端会话状态的,通常由服务端写入,在后续请求中,供服务端读取。

    实现代码:

    配置文件web.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <web-app version="3.0" 
        xmlns="http://java.sun.com/xml/ns/javaee" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
        http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
      <display-name></display-name>    
      
      <servlet>
          <servlet-name>TestCookie</servlet-name>
          <servlet-class>com.cookie.TestCookie</servlet-class>
      </servlet>
      <servlet-mapping>
          <servlet-name>TestCookie</servlet-name>
          <url-pattern>/testCookie</url-pattern>
      </servlet-mapping>
      
      <servlet>
          <servlet-name>GetCookie</servlet-name>
          <servlet-class>com.cookie.GetCookie</servlet-class>
      </servlet>
      <servlet-mapping>
          <servlet-name>GetCookie</servlet-name>
          <url-pattern>/getCookie</url-pattern>
      </servlet-mapping>
      <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
      </welcome-file-list>
    </web-app>

    保存Cookie的servlet:TestCookie.java

    package com.cookie;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.text.SimpleDateFormat;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class TestCookie extends HttpServlet {
        
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            resp.setContentType("text/html;charset=utf-8");
            String username = req.getParameter("username");
            PrintWriter out = resp.getWriter();
            if(username!=""){
                Cookie cName = new Cookie("username",username ); 
                SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
                Cookie cDate = new Cookie("lastVisited",format.format(new java.util.Date()));
                resp.addCookie(cName);
                resp.addCookie(cDate);
                out.println("Cookie 保存成功");
                out.println("<br><br>");
                out.println("<a href='getCookie'>读取Cookie内容</a>");
            }
                out.flush();
                out.close();
            
        
            /*req.getRequestDispatcher(null).forward(req, resp);*/
             
        }
        
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
             this.doPost(req, resp);
        }
    
    }

    读取Cookie的servlet:GetCookie.java

    package com.cookie;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class GetCookie extends HttpServlet {
        
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
             this.doPost(req, resp);
        }
        
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            resp.setContentType("text/html;charset=utf-8");
            PrintWriter out = resp.getWriter();
            out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");
            out.println("<HTML>");
            out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
            out.println("  <BODY>");
            
            Cookie []cookies = req.getCookies();
            Cookie c = null;
            if(cookies!=null){
                for(int i=0;i<cookies.length;i++){
                    c =  cookies[i];
                    if(c.getName().equals("username")){
                        out.println("用户名:"+c.getValue());
                        out.println("<br>");
                    };
                    if(c.getName().equals("lastVisited")){
                        out.println("上次登录时间:"+c.getValue());
                        out.println("<br>");
                    };
                }
            }else{
                out.println("No cookie Existing");
            }
            out.println("</body>");
            out.println("</html>");
            out.flush();
            out.close();
            
        }
        
    
    }

    首页index.jsp:

    <%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
    <%
    String path = request.getContextPath();
    String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
    %>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <base href="<%=basePath%>">
        
        <title>My JSP 'index.jsp' starting page</title>
        <meta http-equiv="pragma" content="no-cache">
        <meta http-equiv="cache-control" content="no-cache">
        <meta http-equiv="expires" content="0">    
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="This is my page">
        <!--
        <link rel="stylesheet" type="text/css" href="styles.css">
        -->
      </head>
      
      <body>
        <form action="testCookie">
            用户名:<input type="text" name="username"/><br>
             <input type="submit" value="提交">
        </form>
      </body>
    </html>

    测试的结果贴图:

    最后成功!!!!!!

    这只是一些测试代码,就还有很多的cookie操作没有写出来,未完待续!!!

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  • 原文地址:https://www.cnblogs.com/zhangminghui/p/3319064.html
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