Cookie
目录
简介
Cookie是服务器发送给客户端、保存在客户端中的一段数据
应用场景：记住密码，浏览记录、购物车
存和取cookie
package com.zhujunwei.servlet;
import java.io.IOException;
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 Demo01 extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置返回给客户端的编码格式
response.setContentType("text/html;charset=utf-8");
//发送cookie给客户端
Cookie cookie = new Cookie("aa", "bb");
//给响应，添加一个cookie
response.addCookie(cookie);
response.getWriter().write("请求成功了...");
//获取客户端带过来的cookie
Cookie[] cookies = request.getCookies();
if(cookies != null){
for (Cookie c : cookies) {
String cookieName = c.getName();
String cookieValue = c.getValue();
System.out.println(cookieName + " = "+ cookieValue);
}
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
第一次访问下面链接时在后台看不到数据，因为我们刚存进去cookie，第二此可以看到aa=bb的结果。
http://localhost:8080/Cookie/Demo01一次存放多个cookie
这个例子一次添加了两个cookie[name=zhangsan,age=18]
package com.zhujunwei.servlet;
import java.io.IOException;
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 Demo02 extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//取客户端发送过来的cookie.
Cookie[] cookies = request.getCookies();
if(cookies != null){
for (Cookie cookie : cookies) {
System.out.println(cookie.getName()+" = "+cookie.getValue());
}
}
//1. 先写cookie 可以给客户端返回多个cookie
Cookie cookie = new Cookie("name", "zhangsan");
//2. 这个cookie的有效期。 默认情况下 ，
//关闭浏览器后，cookie就没有了。 ---> 针对没有设置cookie的有效期。
//有效期以秒计算。
//正值 ： 表示 在这个数字过后，cookie将会失效。
//负值： 关闭浏览器，那么cookie就失效， 默认值是 -1
cookie.setMaxAge(60 * 60 * 24 * 7);
//赋值新的值
//cookie.setValue(newValue);
//用于指定只有请求了指定的域名，才会带上该cookie
// cookie.setDomain(".zhujunwei.com");
//只有访问该域名下的cookieDemo的这个路径地址才会带cookie
// cookie.setPath("/CookieDemo");
response.addCookie(cookie);
Cookie cookie2 = new Cookie("age", "18");
response.addCookie(cookie2);
response.getWriter().write("hello Cookie...");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
获取上次登录时间
登录login.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h2>请输入账号密码登录</h2>
<form action="Demo03" method="get">
账号：<input type="text" name="username"><br>
密码：<input type="text" name="password"><br>
<input type="submit" value="登录">
</form>
</body>
</html>CookieUtil.java类
接收一个Cookie数据和cookie的名字，如果在该数组中找到该cookie就返回该cookie，如果找不到就返回null
package com.zhujunwei.util;
import javax.servlet.http.Cookie;
public class CookieUtil {
/**
* 从一个cookie数组中找到具体我们想要的cookie对象
* @param cookies
* @param name
* @return
*/
public static Cookie findCookie(Cookie[] cookies , String name){
if(cookies != null){
for (Cookie cookie : cookies) {
if(name.equals(cookie.getName())){
return cookie;
}
}
}
return null;
}
}
Demo03.java
用来获取上次登录的时间，并对时间进行更新
package com.zhujunwei.servlet;
import java.io.IOException;
import java.util.Date;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.zhujunwei.util.CookieUtil;
/**
* 获取上次登录时间
* @author Administrator
*
*/
public class Demo03 extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
String userName = request.getParameter("username");
String password = request.getParameter("password");
if("admin".equals(userName) && "123".equals(password)){
//获取cookie last-name --- >
Cookie [] cookies = request.getCookies();
//从数组里面找出我们想要的cookie
Cookie cookie = CookieUtil.findCookie(cookies, "last");
//是第一次登录，没有cookie
if(cookie == null){
Cookie c = new Cookie("last", System.currentTimeMillis()+"");
c.setMaxAge(60*60); //一个小时
response.addCookie(c);
response.getWriter().write("欢迎您, "+userName);
}else{
//1. 去以前的cookie第二次登录，有cookie
long lastVisitTime = Long.parseLong(cookie.getValue());
//2. 输出到界面，
response.getWriter().write("欢迎您, "+userName +",上次来访时间是："+new Date(lastVisitTime));
//3. 重置登录的时间
cookie.setValue(System.currentTimeMillis()+"");
response.addCookie(cookie);
}
}else{
response.getWriter().write("登陆失败 ");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
结果
第一次登录
第二次登录
添加或删除浏览记录
流程图
list.jsp
浏览器中显示
<%@page import="com.zhujunwei.util.CookieUtil"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<a href="ListServlet?id=1">商品1</a><br>
<a href="ListServlet?id=2">商品2</a> <br>
<a href="ListServlet?id=3">商品3</a> <br>
<a href="ListServlet?id=4">商品4</a> <br>
<a href="ListServlet?id=5">商品5</a> <br>
<hr>
<!-- 展示浏览记录 -->
<%
Cookie[] cookies = request.getCookies();
Cookie cookie = CookieUtil.findCookie(cookies, "history");
if (cookie == null) {
%>
<h2>您没有浏览任何商品。</h2>
<%
} else {
String[] ids = cookie.getValue().split("#");
for (String id : ids) {
System.out.println(id);
%>
商品<%=id %>
<%
}
}
%>
<!-- 删除浏览记录 -->
<br>
<a href="Clear">删除浏览记录</a>
</body>
</html>ListServlet.java
处理cookie的添加
package com.zhujunwei;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.zhujunwei.util.CookieUtil;
/**
* 用来添加浏览记录的cookie
* @author Administrator
*
*/
@WebServlet("/ListServlet")
public class ListServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 获取当前用户浏览的商品id
String id = request.getParameter("id");
Cookie[] cookies = request.getCookies();
Cookie cookie = CookieUtil.findCookie(cookies, "history");
// 第一次浏览
if (cookie == null) {
Cookie c = new Cookie("history", id);
c.setMaxAge(60 * 60 * 24);
c.setPath("/Cookie2");
response.addCookie(c);
System.out.println("cookie=" + id);
}
// 不是第一次浏览
else {
String ids = cookie.getValue();
cookie.setValue(id + "#" + ids);
cookie.setMaxAge(60 * 60 * 24);
cookie.setPath("/Cookie2");
response.addCookie(cookie);
System.out.println("cookies=" + cookie.getValue());
}
response.sendRedirect("list.jsp");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
Clear.java
清除浏览记录的Cookie
package com.zhujunwei;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/Clear")
public class Clear extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Cookie cookie = new Cookie("history","");
cookie.setMaxAge(0);//设置立即删除
cookie.setPath("/Cookie2");
response.addCookie(cookie);
response.sendRedirect("list.jsp");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
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我每一次回头，都感觉自己不够努力，所以我不再回头。
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