什么是Session

• 服务器会给每一个用户（浏览器）创建一个Session对象；
• 一个Session独占一个浏览器，只要浏览器没有关闭，这个Session就存在；
• 用户登陆之后，整个网站它都可以访问-------->保存用户的信息；保存购物车的信息

Session和Cookie的区别

• Cookie是把用户的数据写给用户的浏览器，浏览器保存（可以保存多个）
• Session把用户的数据写到用户独占Session中，服务器端保存（保存重要的信息，减少服务器资源的浪费）
• Session对象由服务器创建；
• Cookie：
•  Session：

 

使用场景

• 保存一个登陆用户的信息；
• 购物车信息；
• 在整个项目中经常会使用的数据，我们将它保存在Session中；

使用Session

SessionDemo01.java

package com.godairo.servlet;import pojo.Person;import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;public class SessionDemo01 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//解决乱码request.setCharacterEncoding("UTF-8");request.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=utf-8");//得到SessionHttpSession session = request.getSession();//给Session中存东西session.setAttribute("name",new Person("小可爱",23));//获取Session的IDString sessionid = session.getId();//判断Session是不是新创建的if (session.isNew()){response.getWriter().write("session创建成功，ID为："+sessionid);}else {response.getWriter().write("session已经在服务器中存在，ID为："+sessionid);}//Session创建的时候做了什么事情？
//				Cookie cookie = new Cookie("JSESSIONID",sessionid);
//				response.addCookie(cookie);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doGet(req, resp);}
}

SessionDemo02.java

package com.godairo.servlet;import pojo.Person;import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;public class SessionDemo02 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//解决乱码request.setCharacterEncoding("UTF-8");request.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=utf-8");//得到SessionHttpSession session = request.getSession();Person person = (Person) session.getAttribute("name");System.out.println(person.toString());response.getWriter().write(person.toString());}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doGet(req, resp);}
}

SessionDemo03.java

package com.godairo.servlet;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;public class SessionDemo03 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {HttpSession session = request.getSession();session.removeAttribute("name");//手动注销Sessionsession.invalidate();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

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/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"metadata-complete="true"><servlet><servlet-name>CookieDemo01</servlet-name><servlet-class>com.godairo.servlet.CookieDemo01</servlet-class></servlet><servlet-mapping><servlet-name>CookieDemo01</servlet-name><url-pattern>/c1</url-pattern></servlet-mapping><servlet><servlet-name>CookieDemo02</servlet-name><servlet-class>com.godairo.servlet.CookieDemo02</servlet-class></servlet><servlet-mapping><servlet-name>CookieDemo02</servlet-name><url-pattern>/c2</url-pattern></servlet-mapping><servlet><servlet-name>CookieDemo03</servlet-name><servlet-class>com.godairo.servlet.CookieDemo03</servlet-class></servlet><servlet-mapping><servlet-name>CookieDemo03</servlet-name><url-pattern>/c3</url-pattern></servlet-mapping><servlet><servlet-name>SessionDemo01</servlet-name><servlet-class>com.godairo.servlet.SessionDemo01</servlet-class></servlet><servlet-mapping><servlet-name>SessionDemo01</servlet-name><url-pattern>/s1</url-pattern></servlet-mapping><servlet><servlet-name>SessionDemo02</servlet-name><servlet-class>com.godairo.servlet.SessionDemo02</servlet-class>
</servlet><servlet-mapping><servlet-name>SessionDemo02</servlet-name><url-pattern>/s2</url-pattern></servlet-mapping><servlet><servlet-name>SessionDemo03</servlet-name><servlet-class>com.godairo.servlet.SessionDemo03</servlet-class></servlet><servlet-mapping><servlet-name>SessionDemo03</servlet-name><url-pattern>/s3</url-pattern></servlet-mapping><!--设置Session默认的失效时间--><session-config><!--十五分钟后Session自动失效，以分钟为单位--><session-timeout>1</session-timeout></session-config>
</web-app>

 会话自动过期：web.xml配置

<!--设置Session默认的失效时间-->
<session-config><!--十五分钟后Session自动失效，以分钟为单位--><session-timeout>1</session-timeout>
</session-config>