Java Session验证码案例代码实例解析
案例
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,欢迎您思路
在生成验证码的时候将它的值存入到session中，在比对的时候再取出来进行对比
代码index.jsp
<%-- Created by IntelliJ IDEA. User: tanglei Date: 2020/6/26 Time: 下午12:48 To change this template use File | Settings | File Templates.--%><%@ 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='https://www.haobala.com/login_time_war_exploded/checkCode?time='+new Date().getTime(); } } </script> <style> div{ color: red; } </style></head><body><form action='/login_time_war_exploded/login' 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 src='https://www.haobala.com/login_time_war_exploded/checkCode'></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
<%-- Created by IntelliJ IDEA. User: tanglei Date: 2020/6/26 Time: 下午6:27 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><h1><%=request.getSession().getAttribute('user')%>,欢迎您</h1></body></html>
验证码checkCode.java
package cn.guizimo.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('/checkCode')public class CheckCode extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { int width = 100; int height = 50; //创建图片对象 BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR); //美化 Graphics g = image.getGraphics(); //背景 g.setColor(Color.PINK); g.fillRect(0, 0, width, height); //边框 g.setColor(Color.BLUE); g.drawRect(0, 0, width - 1, height - 1); String str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'; Random ran = new Random(); StringBuilder sb = new StringBuilder(); for (int i = 1; i <= 4; i++) { int index = ran.nextInt(str.length()); char ch = str.charAt(index); sb.append(ch); g.drawString(ch+'',width/5*i,height/2); } String checkCode_session = sb.toString(); //将验证码存入session req.getSession().setAttribute('checkCode_session',checkCode_session); //干扰线 g.setColor(Color.GREEN); 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); } //输出图片到浏览器 ImageIO.write(image, 'jpg', resp.getOutputStream()); } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doPost(req, resp); }}
login.java
package cn.guizimo.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('/login')public class Login extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1.设置request编码 req.setCharacterEncoding('utf-8'); //2.获取参数 String username = req.getParameter('username'); String password = req.getParameter('password'); String checkCode = req.getParameter('checkCode'); //3.先获取生成的验证码 HttpSession session = req.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.jspresp.sendRedirect(req.getContextPath()+'/success.jsp'); }else{//登录失败//存储提示信息到requestreq.setAttribute('login_error','用户名或密码错误');//转发到登录页面req.getRequestDispatcher('/login.jsp').forward(req,resp); } }else{ //验证码不一致 //存储提示信息到request req.setAttribute('cc_error','验证码错误'); //转发到登录页面 req.getRequestDispatcher('/login.jsp').forward(req,resp); } } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doPost(req, resp); }}
测试登录界面
验证码错误
用户名密码错误
登录成功
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