30、31、32、Cookie的操作:
1):创建Cookie和设置共享数据:
Cookie c = new Cookie(String name,String value);
Cookie c = new Cookie("curreentName","wuji");
2):把Cookie放入响应中,把Cookie的共享数据传递给浏览器,由浏览器保存.
response对象.addCookie(c);
3):获取Cookie和Cookie中的数据.(从请求中获取)
4):Cookie的name和value不支持中文.
解决方案:对中文做编码和解码.
//放:
String msg="你好";
String encode = URLEncoder.encode(msg, "UTF-8");
System.out.println(encode);
Cookie c2 = new Cookie("curreentName2",encode);
//取:
String name = cookie.getName();
String value = cookie.getValue();
String decode = URLDecoder.decode(value, "UTF-8");
5):修改Cookie指定名的value值.
方式1: 根据name获取被修改的Cookie对象,在调用setValue方法即可.
方式2: 重新创建一个同名的Cookie.
注意:修改之后,要调用response对象.addCookie(c);
6):Cookie的生命周期:(Cookie中的共享数据可以保留多久)
缺省情况:关闭浏览器Cookie就丢失了.
通过Cookie对象的setMaxAge(int seconds):设置Cookie可以存活多久.
seconds>0:可以存活多少秒.
seconds<0:存放在浏览器进程中,闭浏览器Cookie就丢失了.
seconds=0:删除Cookie.
7):删除Cookie:
Cookie对象.setMaxAge(0);
8):Cookie的缺陷.(重点中的重点)
1>:中文处理麻烦.
2>:多人共用同一台电脑,信息不安全.
3>:一个Cookie只能存储一个简单类型的数据.
若要同时存储,账号,密码,邮件等等.
主要的原因是:Cookie的value只能存储String,不能存Object.
4>:Cookie的大小和数量限制:
Cookie大小限制在4KB之内；
* 一台服务器在一个客户端最多保存20个Cookie；
* 一个浏览器最多可以保存300个Cookie；
5>:Cookie的原理:把共享数据存储在浏览器中.
每次请求,再把共享数据带到服务端.
代码：
1 package com.day07.web.demo2.controller; 2 ?3 import javax.servlet.ServletException; 4 import javax.servlet.annotation.WebServlet; 5 import javax.servlet.http.Cookie; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 import java.io.IOException;10 import java.io.PrintWriter;11 12 /**13 ?* Created by Administrator on 2017/12/7.14 ?*/15 @WebServlet("/cookie")16 public class CookieServlet extends HttpServlet {17 ????@Override18 ????public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {19 ????????//请求乱码处理20 ????????req.setCharacterEncoding("utf-8");21 ????????//响应乱码处理22 ????????resp.setContentType("text/html;charset=UTF-8");23 ????????//操作cookie24 25 ????????//增加26 ????????Cookie cookie1 = new Cookie("name1","wuji1");27 ????????resp.addCookie(cookie1);28 ????????Cookie cookie2 = new Cookie("name2","wuji2");29 ????????resp.addCookie(cookie2);30 ????????//删除31 ???????/* 6):Cookie的生命周期:(Cookie中的共享数据可以保留多久)32 ????????????????缺省情况:关闭浏览器Cookie就丢失了.33 ????????????????通过Cookie对象的setMaxAge(int seconds):设置Cookie可以存活多久.34 ????????????????seconds>0:可以存活多少秒.35 ????????????????seconds<0:存放在浏览器进程中,闭浏览器Cookie就丢失了.36 ????????????????seconds=0:删除Cookie.37 ????????7):删除Cookie:38 ????????Cookie对象.setMaxAge(0);*/39 ????????cookie1.setMaxAge(0);40 ????????//必须 ?resp.addCookie(cookie); 才可以生效41 ????????resp.addCookie(cookie1);42 ????????//修改43 44 ????????//查询45 46 ????????//获取输出对象47 ????????PrintWriter writer = resp.getWriter();48 ????????//输出信息49 ????????writer.println("你好师姐!");50 51 52 ????}53 } 1 package com.day07.web.demo2.controller; 2 ?3 import javax.servlet.ServletException; 4 import javax.servlet.annotation.WebServlet; 5 import javax.servlet.http.Cookie; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 import java.io.IOException;10 import java.io.PrintWriter;11 12 /**13 ?* Created by Administrator on 2017/12/7.14 ?*/15 @WebServlet("/cookie2")16 public class Cookie2Servlet extends HttpServlet {17 ????@Override18 ????public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {19 ????????//请求乱码处理20 ????????req.setCharacterEncoding("utf-8");21 ????????//响应乱码处理22 ????????resp.setContentType("text/html;charset=UTF-8");23 ????????//操作cookie24 25 ????????//删除26 ????????//修改27 28 ????????//查询29 ????????Cookie[] cookies = req.getCookies();30 ????????for (int i=0;i<cookies.length;i++){31 ????????????Cookie cookie = cookies[i];32 ????????????//取key33 ????????????String name = cookie.getName();34 ????????????//取值35 ????????????String value = cookie.getValue();36 ????????????//打印37 ????????????System.out.println(name+"="+value);38 39 ????????????cookie.setValue("zhaoming");40 ????????????resp.addCookie(cookie);41 ????????}42 43 ????????//获取输出对象44 ????????PrintWriter writer = resp.getWriter();45 ????????//输出信息46 ????????writer.println("你好师姐----获取cookie的数据!");47 48 49 ????}50 }04_web基础（）之cookie操作
原文地址：https://www.cnblogs.com/newAndHui/p/8777916.html