会话跟踪之 session （1）session 也是域对象之一，它的范围是在一个会话范围内有效。session 既然是域对象，那么当然就要有 getAttribute() 和 setAttribute() 系列方法了。 （2）在一个会话内共享一个 session 对象，所以 session 中可以保存一个会话内的数据。例如当前用户的信息。 （3）session 的范围大于 request，可以在一个会话中多个请求之间共享数据。但 session 的范围小于 ServletContext(application)， session 不能在多个用户之间共享数据。 （4）目前所学过的域对象的作用范围：
ServletContext > HttpSession > HttpServletRequest获取 session 对象 （1）使用 request.getSession() 方法就可以获取 session 对象。 （2）有了 session，就不用使用 Cookie 来跟踪会话了！但是 session 不能像 Cookie 那样长命，一旦用户关闭浏览器窗口，那么 session 就死掉了。
示例
以上操作完整源码 web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <servlet> <servlet-name>RegistServlet</servlet-name> <servlet-class>com.wyx.cookie.RegistServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>RegistServlet</servlet-name> <url-pattern>/servlet/RegistServlet</url-pattern> </servlet-mapping> <servlet> <servlet-name>Regist1Servlet</servlet-name> <servlet-class>com.wyx.cookie.Regist1Servlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>Regist1Servlet</servlet-name> <url-pattern>/servlet/Regist1Servlet</url-pattern> </servlet-mapping> </web-app>regist
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>用户注册第一步</title> </head> <body> <h1>用户注册</h1> <hr> <form action="/session_demo/servlet/RegistServlet" method="post"> 用户名：<input type="text" name="username"><br> 密 码：<input type="password" name="password"><br> <input type="submit" value="下一步"> </form> </body> </html>regist1
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>用户注册第二步</title> </head> <body> <h1>用户注册</h1> <hr> <form action="/session_demo/servlet/Regist1Servlet" method="post"> 性别：<input type="radio" name="gender" value="1">男 <input type="radio" name="gender" value="2">女 <br> 职位： <select name="job"> <option value="">请选择</option> <option value="1">教授</option> <option value="2">副教授</option> </select> <br> <input type="submit" value="完成"> </form> </body> </html>RegistServlet
package com.wyx.cookie; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class RegistServlet extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setCharacterEncoding("UTF-8"); String username = req.getParameter("username"); String password = req.getParameter("password"); // 获得session对象 HttpSession session = req.getSession(); // 设置session的属性，在session中的属性在整次会话（浏览器不关闭）都有作用 session.setAttribute("username", username); session.setAttribute("password", password); req.getRequestDispatcher("/regist1.html").forward(req, resp); } }Regist1Servlet
package com.wyx.cookie; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class Regist1Servlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 获得性别 String gender = request.getParameter("gender"); // 获得职位 String job = request.getParameter("job"); // 根据request来获取session HttpSession session = request.getSession(); // 从session获取用户名和密码 String username = (String) session.getAttribute("username"); String password = (String) session.getAttribute("password"); // 获得session的id，session利用id和浏览器的cookie进行绑定用来区分会话 String sessionId = session.getId(); System.out.println(sessionId); response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); String genderText = ""; if ("1".equals(gender)) { genderText = "男"; } else if ("2".equals(gender)) { genderText = "女"; } String jobText = ""; if ("1".equals(job)) { jobText = "教授"; } else if ("2".equals(job)) { jobText = "副教授"; } response.getWriter().println("<h1>注册成功</h1>"); response.getWriter().println("<hr>"); response.getWriter().println("用户名：" + username + "<br>"); response.getWriter().println("密码：" + password + "<br>"); response.getWriter().println("性别：" + genderText + "<br>"); response.getWriter().println("职位：" + jobText + "<br>"); } }工程文件下载
如有错误，欢迎指正！
