标签：大小 相同 选择 war session共享 自动完成 情况下 uil package
一、入门
1. 概念：服务器端会话技术，在一次会话的多次请求间共享数据，将数据保存在服务器端的对象中。HttpSession 2. 快速入门： 1. 获取HttpSession对象： HttpSession session = request.getSession(); 2. 使用HttpSession对象： Object getAttribute(String name) void setAttribute(String name, Object value) void removeAttribute(String name) 3. 原理 * Session的实现是依赖于Cookie的。 --------------------------------- package cn.itcast.session; 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("/sessionDemo1") public class SessionDemo1 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //使用session共享数据 //1.获取session HttpSession session = request.getSession(); //2.存储数据 session.setAttribute("msg","hello session"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } } --------------------------------- package cn.itcast.session; 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("/sessionDemo2") public class SessionDemo2 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //使用session获取数据 //1.获取session HttpSession session = request.getSession(); //2.获取数据 Object msg = session.getAttribute("msg"); System.out.println(msg); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } }
二、session细节
1. 当客户端关闭后，服务器不关闭，两次获取session是否为同一个？
* 默认情况下。不是。 * 如果需要相同，则可以创建Cookie,键为JSESSIONID，设置最大存活时间，让cookie持久化保存。 Cookie c = new Cookie("JSESSIONID",session.getId()); c.setMaxAge(60*60); response.addCookie(c); --------------------------------- package cn.itcast.session; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*; import java.io.IOException; @WebServlet("/sessionDemo3") public class SessionDemo3 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1.获取session HttpSession session = request.getSession(); System.out.println(session); //期望客户端关闭后，session也能相同 Cookie c = new Cookie("JSESSIONID",session.getId()); c.setMaxAge(60*60); response.addCookie(c); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } }
2. 客户端不关闭，服务器关闭后，两次获取的session是同一个吗？
* 不是同一个，但是要确保数据不丢失。tomcat自动完成以下工作 * session的钝化： * 在服务器正常关闭之前，将session对象系列化到硬盘上 * session的活化： * 在服务器启动后，将session文件转化为内存中的session对象即可。
3. session什么时候被销毁？
1. 服务器关闭 2. session对象调用invalidate() 。 3. session默认失效时间 30分钟 选择性配置修改 web.xml <session-config> <session-timeout>30</session-timeout> </session-config>
4.session的特点
1. session用于存储一次会话的多次请求的数据，存在服务器端 2. session可以存储任意类型，任意大小的数据 session与Cookie的区别： 1. session存储数据在服务器端，Cookie在客户端 2. session没有数据大小限制，Cookie有 3. session数据安全，Cookie相对于不安全
三、验证码案例
1、需求
1. 案例需求： 1. 访问带有验证码的登录页面login.jsp 2. 用户输入用户名，密码以及验证码。 * 如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误 * 如果验证码输入有误，跳转登录页面，提示：验证码错误 * 如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您
2、实现
login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>login</title> <script> window.onload = function(){ document.getElementById("img").onclick = function(){ this.src="/day16/checkCodeServlet?time="+new Date().getTime(); } } </script> <style> div{ color: red; } </style> </head> <body> <form action="/day16/loginServlet" method="post"> <table> <tr> <td>用户名</td> <td><input type="text" name="username"></td> </tr> <tr> <td>密码</td> <td><input type="password" name="password"></td> </tr> <tr> <td>验证码</td> <td><input type="text" name="checkCode"></td> </tr> <tr> <td colspan="2"><img id="img" src="/day16/checkCodeServlet"></td> </tr> <tr> <td colspan="2"><input type="submit" value="登录"></td> </tr> </table> </form> <div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%></div> <div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %></div> </body> </html>
success.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <h1><%=request.getSession().getAttribute("user")%>,欢迎您</h1> </body> </html>
CheckCodeServlet.java
package cn.itcast.servlet; import javax.imageio.ImageIO; 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 java.awt.*; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random; @WebServlet("/checkCodeServlet") public class CheckCodeServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int width = 100; int height = 50; //1.创建一对象，在内存中图片(验证码图片对象) BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //2.美化图片 //2.1 填充背景色 Graphics g = image.getGraphics();//画笔对象 g.setColor(Color.PINK);//设置画笔颜色 g.fillRect(0,0,width,height); //2.2画边框 g.setColor(Color.BLUE); g.drawRect(0,0,width - 1,height - 1); String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789"; //生成随机角标 Random ran = new Random(); StringBuilder sb = new StringBuilder(); for (int i = 1; i <= 4; i++) { int index = ran.nextInt(str.length()); //获取字符 char ch = str.charAt(index);//随机字符 sb.append(ch); //2.3写验证码 g.drawString(ch+"",width/5*i,height/2); } String checkCode_session = sb.toString(); //将验证码存入session request.getSession().setAttribute("checkCode_session",checkCode_session); //2.4画干扰线 g.setColor(Color.GREEN); //随机生成坐标点 for (int i = 0; i < 10; i++) { int x1 = ran.nextInt(width); int x2 = ran.nextInt(width); int y1 = ran.nextInt(height); int y2 = ran.nextInt(height); g.drawLine(x1,y1,x2,y2); } //3.将图片输出到页面展示 ImageIO.write(image,"jpg",response.getOutputStream()); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
LoginServlet.java
package cn.itcast.servlet; 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("/loginServlet") public class LoginServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1.设置request编码 request.setCharacterEncoding("utf-8"); //2.获取参数 String username = request.getParameter("username"); String password = request.getParameter("password"); String checkCode = request.getParameter("checkCode"); //3.先获取生成的验证码 HttpSession session = request.getSession(); String checkCode_session = (String) session.getAttribute("checkCode_session"); //删除session中存储的验证码 session.removeAttribute("checkCode_session"); //3.先判断验证码是否正确 if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){ //忽略大小写比较 //验证码正确 //判断用户名和密码是否一致 if("zhangsan".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库 //登录成功 //存储信息，用户信息 session.setAttribute("user",username); //重定向到success.jsp response.sendRedirect(request.getContextPath()+"/success.jsp"); }else{ //登录失败 //存储提示信息到request request.setAttribute("login_error","用户名或密码错误"); //转发到登录页面 request.getRequestDispatcher("/login.jsp").forward(request,response); } }else{ //验证码不一致 //存储提示信息到request request.setAttribute("cc_error","验证码错误"); //转发到登录页面 request.getRequestDispatcher("/login.jsp").forward(request,response); } } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } }
标签：大小 相同 选择 war session共享 自动完成 情况下 uil package
原文地址：https://www.cnblogs.com/weiyiming007/p/11640316.html
