1、书写servlet，获取验证码的数据，并对验证码进行校验
public class ValidateServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub String code = request.getParameter("code"); HttpSession session = request.getSession(); String randStr = (String)session.getAttribute("randStr"); response.setCharacterEncoding("gb2312"); PrintWriter out = response.getWriter(); if(!code.equals(randStr)){ out.println("验证码错误"); } else{ out.println("验证码正确......"); } } }
2、创建登录界面
<%@ page language="java" pageEncoding="gb2312"%> <html> <body> <script type="text/javascript"> function refresh(){ document.getElementById("imgValidate").src="validate.jsp?random="+Math.random(); } </script> 欢迎登录本系统<BR> <form name="loginForm" action="ValidateServlet" method="post"> 请您输入账号:<input type="text" name="account" /><BR> 请您输入密码: <input type="password" name="password" /><BR> 请输入验证码:<input type="text" name="code" size="10"/> <img name="imgValidate" id="imgValidate" src="validate.jsp" onclick="refresh()"/><BR> <input type="submit" value="登录"/> </form> </body> </html>
点击验证码的图片之后会调用validate.jsp生成验证码，但是，在这个过程中会传递一个随机数，在validate.jsp中对数据进行模糊处理，并将数据存储在session中。
3、创建生成验证码图片的jsp
<%@ page language="java" import="java.awt.*" import="java.awt.image.BufferedImage" import="java.util.*" import="javax.imageio.ImageIO" pageEncoding="gb2312"%> <% response.setHeader("Cache-Control","no-cache"); // 在内存中创建图象 int width = 60, height = 20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); //获取画笔 Graphics g = image.getGraphics(); //设定背景色 g.setColor(new Color(200, 200, 200)); g.fillRect(0, 0, width, height); //取随机产生的验证码(4位数字) Random rnd = new Random(); int randNum = rnd.nextInt(8999) + 1000; String randStr = String.valueOf(randNum); //将验证码存入session session.setAttribute("randStr", randStr); //将验证码显示到图象中 g.setColor(Color.black); g.setFont(new Font("", Font.PLAIN, 20)); g.drawString(randStr, 10, 17); // 随机产生100个干扰点，使图象中的验证码不易被其他程序探测到 for (int i = 0; i < 100; i++){ int x = rnd.nextInt(width); int y = rnd.nextInt(height); g.drawOval(x, y, 1, 1); } // 输出图象到页面 ImageIO.write(image, "JPEG", response.getOutputStream()); out.clear(); out = pageContext.pushBody(); %>
4、在web.xml中配置servlet
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <display-name>yanzheng</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>ValidateServlet</servlet-name> <servlet-class>pers.zhb.test.ValidateServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ValidateServlet</servlet-name> <url-pattern>/ValidateServlet</url-pattern> </servlet-mapping> </web-app>