Cookie简介

原创

Cooike对象是由服务器产生并保存到客户端（内存或文件中）的信息。

对于Cookie对象的使用，一般需要两步操作。首先由服务器创建Cookie对象保存到客户端，然后在JSP页面或者Servlet中读取Cookie并进行处理。

Cookie的相关方法

方法	说明
Cookie(String name,String value)	构造函数，创建一个Cookie对象
void response.addCookie(Cookie c)	向客户机添加一个Cookie对象
Cookie request.getCookies()	用于取得所有Cookie对象的数据，存放到一个数组中
String getName()	取得Cookie对象的属性名
String getValue()	取得Cookie对象的属性对应的属性值
setMaxAge(int expiry)	设置cookie有效时间，以秒为单位，设置了有效时间的cookie将以文件形式保存在客户端，否则只是存储在浏览器的内存区域中

String name="zhangsan";
Cookie c=new Cookie("user",name);    //创建Cookie对象，对象名为user而不是c
response.add(c);    //将Cookie对象添加到响应中，保存到客户端

Cookie cookie[]=request.getCookies();    //获得客户端所有的Cookie对象
for(int i=0;i<cookie.length;i++){
        if(cookie[i].getName().equals("user"){
                out.print(cookie[i].getValue());
        }    
}

在一个JSP页面中创建Cookie对象保存到客户端

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
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 'cookie1.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>
      <%
          Cookie c1=new Cookie("name","zhangsan"); 
          c1.setMaxAge(60*60);
          response.addCookie(c1);
          Cookie c2=new Cookie("user","lisi");
          c2.setMaxAge(60*60);
          response.addCookie(c2);
          Cookie c3=new Cookie("account","zhaowu");
          c3.setMaxAge(60*60);
          response.addCookie(c3);
      %>
  </body>
</html>

无需跳转则可以在另一个JSP页面获取Cookie对象的值

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
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 'cookie2.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>
    <%
        Cookie cookie[]=request.getCookies();
        if(cookie!=null){
            out.print(cookie.length);
            System.out.println();
            for(int i=0;i<cookie.length;i++){
                out.print(cookie[i].getValue());
                System.out.println();
            }
        }else{
            out.print("no exist cookie");
        }
    %>
  </body>
</html>

22:00:06

2018-11-16