1 使用Servlet实现验证码，涉及的知识点主要为java 绘图技术与session保存数据。
HTML页面
1 <html>
2 <image src=‘images/logo1.jpg‘ /><hr/>
3 <head><br/><title>登录</title> <br/><h1> 欢迎登录</h1></head>
4 <body>
5 <form action=‘/LoginValid/LoginVerify‘ method=‘post‘ >
6 用户id：<input type=‘text‘ name=‘userid‘ value=‘‘>
7 用户密码：<input type=‘password‘ name=‘password‘ value=‘‘>
9 验证码：<input type=‘text‘ name=‘inputCode‘ /> <img id=‘imgObj‘ src=‘/LoginValid/CreateCode2‘ /><a href=‘javascript:changeImg()‘ >换一张</a>
10 <input type=‘submit‘ value=‘登录‘ />
11 </form>
12 </body>
13 <script type=‘text/javascript‘>
14 function changeImg() { var time = new Date(); document.getElementById(‘imgObj‘).src=‘/LoginValid/CreateCode2?d=‘+time; }
15 </script>
16 </html>
生成验证码的工具类
1 public class CodeUtil {
2
3 //图片宽度
4 private static final int IMG_W=120;
5 //图片高度
6 private static final int IMG_H=30;
7 //验证码字符个数
8 private static final int NUM_CHS=5;
9 //验证码包含的具体字符
10 private static char[] chs = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890".toCharArray();
11 private static Random rand = new Random();
12
13 //图片x轴，y轴的位置基数
14 private static int codeX = 20;
15 private static int codeY = 25;
16
17 //字体大小
18 private static int fontH = 25;
19
20 public static Map<String, Object> generateImage()
21 {
22 BufferedImage image = new BufferedImage(IMG_W, IMG_H, BufferedImage.TYPE_INT_RGB);
23 Graphics g = image.getGraphics();
24
25 //设置图片背景色为白色
26 g.setColor(Color.WHITE);
27 g.fillRect(0, 0, IMG_W, IMG_H);
28
29 //设置字体大小
30 Font font = new Font("Fixedsys", Font.BOLD, fontH);
31 g.setFont(font);
32
33 //画边框
34 g.setColor(Color.BLACK);
35 g.drawRect(0, 0, IMG_W, IMG_H);
36
37 g.setColor(Color.BLACK);
38 //随机产生30条干扰线
39 for(int i=0; i<30; i++)
40 {
41 int x = rand.nextInt(IMG_W);
42 int y = rand.nextInt(IMG_H);
43 int xl = rand.nextInt(20);
44 int yl = rand.nextInt(20);
45
46 g.drawLine(x, y, xl, yl);
47 }
48
49 StringBuilder sb = new StringBuilder();
50 for(int i=0; i<NUM_CHS; i++)
51 {
52 //从字符串中随机获取一个字符
53 String code = String.valueOf(chs[rand.nextInt(chs.length)]);
54 //随机设置画笔颜色
55 g.setColor(new Color(rand.nextInt(255),rand.nextInt(255),rand.nextInt(255)));
56 g.drawString(code, (i+1)*codeX, codeY);
57 sb.append(code);
58 }
59
60 Map<String, Object> map = new HashMap<String, Object>();
61 map.put("code", sb.toString());
62 map.put("codeImage", image);
63 return map;
64
65 }
66
67 }
后台产生验证码的Servlet
1 //禁止浏览器缓存随机图片
2 response.setDateHeader("Expires",-1);
3 response.setHeader("Cache-Control", "no-cache");
4 response.setHeader("Pragma", "no-cache");
5
6 //通知客户端以图片的方式打开发送过去的数据
7 response.setHeader("Content-Type", "image/jpeg");
8
9 Map<String, Object> map = CodeUtil.generateImage();
10 //将验证码保存至session
11 request.getSession().setAttribute("checkCode", map.get("code"));
12 ImageIO.write((RenderedImage)map.get("codeImage"), "jpg", response.getOutputStream());
后台验证用户输入的验证码与显示的是否一致的Servlet类
2 HttpSession session = request.getSession();
3 String seCode = (String)session.getAttribute("checkCode");
4 String inputCode = (String)request.getParameter("inputCode");
5 if(seCode.equals(inputCode))
6 {
7 request.getRequestDispatcher("/Main").forward(request, response);
8 }
9 else
10 {
11 request.getRequestDispatcher("/Err").forward(request, response);
12 }
原文地址：https://www.cnblogs.com/Latiny/p/8338340.html
时间： 2024-08-30 12:08:37