Cookie和Session

会话：

有状态会话：
客户端知道发起请求的是谁

无状态会话：

不知道发起请求的是谁只知道有请求

http是无状态请求

保存会话信息的两种技术：

可以通过Cookie和Session储存会话信息

cookie：客户端技术信心存在客户端

由服务器创建，通过响应发送给客户端，并且保存在客户浏览器的一块信息浏览器下次向服务器发起请求时会携带这块信息并发送到服务器上

工作流程

后端中设置cookie

package com.qcby.test;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;/*** Servlet implementation class SetCookie*/
@WebServlet("/SetCookie")
public class SetCookie extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public SetCookie() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub//response.getWriter().append("Served at: ").append(request.getContextPath());//服务器创建cookie对象Cookie cookie=new Cookie("username","admin");//设置cookie有效期 有效期小于0说明是临时的 浏览器关掉就没有了 =0则是删除这个cookiecookie.setMaxAge(60*60);//将cookie相应给客户端response.addCookie(cookie);}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubdoGet(request, response);}}

后端中读取cookie

package com.qcby.test;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;/*** Servlet implementation class GetCookie*/
@WebServlet("/GetCookie")
public class GetCookie extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public GetCookie() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub//response.getWriter().append("Served at: ").append(request.getContextPath());Cookie[] cookies=request.getCookies();for(int i=0;i<cookies.length;i++){System.out.println(cookies[i].getName()+"-->"+cookies[i].getValue());}}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubdoGet(request, response);}}

js中创建cookie

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script>document.cookie="password=123456;max-age="+30*60;var getCookie=function(name){var cookies=document.cookie.split(";");//以";"做分割for(var i=0;i<cookies.length;i++){if(cookies[i].trim().indexOf(name)==0)//子串中是否包含name{return cookies[i].trim().substring(name.length+1)}}return ""}console.log(getCookie("password"))
</script>
</head>
<body></body>
</html>

使用js的cookie插件创建cookie

jQuery Cookie 插件 | 菜鸟教程去这下插件有用法解释

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script src="https://cdn.staticfile.org/jquery/3.4.0/jquery.min.js"></script>
<script src="https://cdn.staticfile.org/jquery-cookie/1.4.1/jquery.cookie.min.js"></script>
<script>$.cookie("color","pink")
</script>
</head>
<body></body>
</html>

cookie的优缺点

优点：

可设置到期规则重复访问时不需要再次登录

包含简单的键值对数据持久

缺点：
大小受限制

浏览器可以设置cookie禁用

cookie可被篡改不安全

session：服务端技术信息存在服务端只能在后端中进行

为每次会话创建一个会话对象也就是session对象存储和取数据都在这个对象中

工作流程：

创建session

package com.qcby.test;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;/*** Servlet implementation class SetSession*/
@WebServlet("/SetSession")
public class SetSession extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public SetSession() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub//response.getWriter().append("Served at: ").append(request.getContextPath());HttpSession session=request.getSession();session.setAttribute("account", "admin");session.setAttribute("password", "123456");session.setAttribute("demo", "777");}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubdoGet(request, response);}}

获取

package com.qcby.test;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;/*** Servlet implementation class GetSession*/
@WebServlet("/GetSession")
public class GetSession extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public GetSession() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub//response.getWriter().append("Served at: ").append(request.getContextPath());HttpSession session=request.getSession();System.out.println(session.getId());//获取jsessionidSystem.out.println(session.getAttribute("account"));System.out.println(session.getAttribute("password"));System.out.println(session.getAttribute("demo"));session.removeAttribute("demo");//删除demosession.invalidate();//销毁session 关掉浏览器也可以实现 jsessionid就会改变session.setMaxInactiveInterval(60*60);//设置有效期//session生命周期//第一次使用到session的请求创建session//浏览器关闭或者服务器关闭或者手动销毁或者到期超时失效}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubdoGet(request, response);}}

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