### session setAttribute getAttribute removeAttribute invalidate //设置 session 失效，当用户执行退出登录时，调用该方法 ### Cookie Cookie 时服务端在 HTTP 响应过程中附带传送给浏览器的一个文本文件，一旦浏览器保存了某个 Cookie，那么在以后的每次访问中都会将这个 Cookie 传递，服务端在做响应的时候会再次将 Cookie 传给浏览器，以此类推，如此 Cooki 就可以在客户端和服务端之间来回传递，从而实现数据交互的功能。 Cookie 常用方法 - new Cookie(String name,String value) 创建一个 Cookie 对象，用键值对的形式来存储数据 ```jsp Cookie cookie = new Cookie("age","22"); response.addCookie(cookie); ``` - request.getCookies() 获取 request 中的所有 Cookie - void setMaxAge(int age) 设置 Cookie 的有效期，以秒为单位 - int getMaxAge() 获取 Cookie 的有效期 - void setValue(String value) 修改 Cookie 的 value 值 - String getName() 获取 Cookie 的 name 值 - String getValue() 获取 Cookie 的 value 值 ### Session 和 Cookie 的区别 Session 保存在服务端，Cookie 保存在客户端。 Session 存储的数据类型 Object，Cookie 只能存储 String Session 会随着会话的结束而销毁，Cookie 可长期保存在客户端浏览器中 Session 保存重要信息，Cookie 保存不重要的信息 ### JSP 内置对象作用域 page 作用域：对应的内置对象是 pageContext request 作用域：对应的内置对象是 request session 作用域：对应的内置对象是 session application 作用域：对应的内置对象是 application page 作用域只在当前页面有效，对应 JSP。 request 作用域在同一次请求内有效，对应请求。 session 作用域在同一次会话中有效，对应会话。 application 作用域对应的是整个 Web 应用，只要 Tomcat 不重启，application 就可用，对应 Tomcat。
LoginServlet.java
package com.southwind.controller; 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; import java.io.IOException; @WebServlet("/login.do") public class LoginServlet extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String username = req.getParameter("username"); String password = req.getParameter("password"); if(username.equals("zhangsan")&&password.equals("123")){ //用户信息保存到session中 HttpSession session = req.getSession(); session.setAttribute("username",username); resp.sendRedirect("index.jsp"); }else{ resp.sendRedirect("login.jsp"); } } }
LogoutServlet.java
package com.southwind.controller; 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; import java.io.IOException; @WebServlet("/logout.do") public class LogoutServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { HttpSession session = req.getSession(); session.invalidate(); resp.sendRedirect("index.jsp"); } }
cookie.jsp
<%-- Created by IntelliJ IDEA. User: southwind Date: 2019-07-09 Time: 20:40 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <% //创建 Cookie Cookie cookie = new Cookie("age","22"); response.addCookie(cookie); %> </body> </html>
count.jsp
<%-- Created by IntelliJ IDEA. User: southwind Date: 2019-07-09 Time: 21:47 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <% Integer num = (Integer) application.getAttribute("num"); if(num == null){ num = 0; } num++; application.setAttribute("num",num); %> 您是当前第<%=num%>位访客。 </body> </html>
getCookie.jsp
<%-- Created by IntelliJ IDEA. User: southwind Date: 2019-07-09 Time: 20:48 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <% Cookie[] cookies = request.getCookies(); for (Cookie cookie:cookies){ System.out.println(cookie.getMaxAge()); // System.out.println(cookie.getName()+"-"+cookie.getValue()); } %> </body> </html>
index.jsp
<%-- Created by IntelliJ IDEA. User: southwind Date: 2019-07-09 Time: 20:13 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>$Title$</title> </head> <body> 欢迎回来！<% String username = (String) session.getAttribute("username"); %> <%=username%> <a href="/logout.do">退出登录</a> </body> </html>
login.jsp
<%-- Created by IntelliJ IDEA. User: southwind Date: 2019-07-09 Time: 20:20 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <form action="/login.do" method="post"> <input type="text" name="username"/> <input type="password" name="password"/> <input type="submit" value="登录"/> </form> </body> </html>
pageContext.jsp
<%-- Created by IntelliJ IDEA. User: southwind Date: 2019-07-09 Time: 21:39 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <% application.setAttribute("name","zhangsan"); request.getRequestDispatcher("target.jsp").forward(request,response); %> </body> </html>
target.jsp
<%-- Created by IntelliJ IDEA. User: southwind Date: 2019-07-09 Time: 21:41 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <% String name = (String)application.getAttribute("name"); %> <%=name%> </body> </html>
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0"> </web-app>
