)验证码使用一个CheckCodeSerlvet产生，通过<img class="lazyload" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC" data-original=""/>发送请求，将验证码绑定到HttpSession中
)产生的验证码一定要在输出到浏览器之前绑定到HttpSession中
)设置验证码禁止缓存要在输出到浏览器之前
)所有响应头的设置放置在最先
java代码
LoginServlet
import java.io.IOException;import java.io.PrintWriter;import java.util.zip.Checksum;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class LoginServlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 收集客户端填入的验证码 String checkCodeClient = request.getParameter("checkCodeClient"); // 取得服务端填入的验证码 String checkCodeServer = (String) request.getSession().getAttribute( "checkCodeServer"); // 设置字体 response.setContentType("text/html;charset=UTF-8"); //判断的。通过客户端与服务端 if (checkCodeClient != null && checkCodeClient.trim().length() > 0 && checkCodeServer != null && checkCodeServer.equals(checkCodeClient)) { response.getWriter().write("验证码正确"); } else { response.getWriter().write("验证码出错"); } }}CheckCodeServlet
import javax.imageio.ImageIO;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 CheckCodeServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //缓存 response.setHeader("expires","-1"); response.setHeader("cache-control","no-cache"); //没有缓成 response.setHeader("pragma","no-cache"); String token = Token.getNum(); //将验证码绑定到域对象 HttpSession session = request.getSession(); session.setAttribute("checkCodeServer",token); //在内存生存一个图片 BufferedImage image = new BufferedImage(50,25,BufferedImage.TYPE_INT_RGB); //获取画笔 Graphics g = image.getGraphics(); //设置大小 g.drawString(token,15,15); //增加干扰线 for(int i=0;i<10;i++) { Random r = new Random(); int x1 = r.nextInt(50); int y1 = r.nextInt(25); g.drawLine(x1, y1, x1+4,y1+4); } //写到浏览器 ImageIO.write(image,"JPG",response.getOutputStream()); }}//用于产生随机数class Token{ public static String getNum(){ Random r = new Random(); int num = r.nextInt(10000); return num + ""; }}html代码
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>login.html</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body> <form action="/day04/LoginServlet" method="post"> <table border="1" align="center"> <caption>用户登陆验证码</caption> <tr> <th>用户名</th> <td><input type="text" name="username"/></td> </tr> <tr> <th>密码</th> <td><input type="password" name="password"/></td> </tr> <tr> <th>验证码</th> <td> <input type="text" name="checkCodeClient"/> </td> <td> <img class="lazyload" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC" data-original="/day04/CheckCodeServlet"/> </td> </tr> <tr> <td colspan="2" align="center"> <input type="submit" value="提交"/> </td> </tr> </table> </form> </body></html>
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