验证码的简单实现

 1 public class IdCodeServlet extends HttpServlet {
 2     private Random rand = new Random();
 3     private int randNum(int begin,int end){
 4         return rand.nextInt(end-begin)+begin;
 5     }
 6     public void doGet(HttpServletRequest request, HttpServletResponse response)
 7             throws ServletException, IOException {
 8         
 9         response.setDateHeader("Expires", -1);
10         response.setHeader("Cache-Control", "no-cache");
11         response.setHeader("Pragma", "no-cache");
12         //1.在内存中构建出一张图片
13         int height = 30; 
14         int width = 120;
15         int xpyl = 5;
16         int ypyl = 22;
17         int bang = 20;
18         BufferedImage img = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
19         //2.获取图像上的画布
20         Graphics2D g = (Graphics2D) img.getGraphics();
21         //3.设置背景色
22         g.setColor(Color.LIGHT_GRAY);
23         g.fillRect(0, 0, width, height);
24         //4.设置边框
25         g.setColor(Color.BLUE);
26         g.drawRect(0, 0, width-1, height-1);
27         //5.画干扰线
28         for(int i = 0;i<5;i++){
29             g.setColor(Color.RED);
30             g.drawLine(randNum(0, width), randNum(0, height), randNum(0, width), randNum(0, height));
31         }
32         //6.写字
33          String base = "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";
34         for(int i = 0; i<4;i++){
35             g.setColor(new Color(randNum(0,255),randNum(0,255),randNum(0,255)));
36             g.setFont(new Font("黑体",Font.BOLD,bang));
37             int r = randNum(-45,45);
38             g.rotate(1.0*r/180*Math.PI, xpyl+(i*30), ypyl);
39             g.drawString(base.charAt(randNum(0, base.length()-1))+"", xpyl+(i*30), ypyl);
40             g.rotate(1.0*-r/180*Math.PI, xpyl+(i*30), ypyl);
41         }
42         //将图片输出到浏览器
43         ImageIO.write(img, "jpg", response.getOutputStream());
44     }
45 
46 
47     public void doPost(HttpServletRequest request, HttpServletResponse response)
48             throws ServletException, IOException {
49         doGet(request, response);
50     }
51 
52 }

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
    <script type="text/javascript">
    	function changeImg(img){
    		img.src="/IdCode/servlet/IdCodeServlet?time="+new Date().getTime();
    	}
    </script>
  </head>
  <body>
  	<form action="#" method="POST">
  		用户名:<input type="text" name="username"/>
  		密码:<input type="password" name="password"/>
  		验证码:<input type="text" name="valistr"/>
  		<img src="/IdCode/servlet/IdCodeServlet" style="cursor: pointer;" onclick="changeImg(this)"/>
  		<input type="submit" value="注册" />
  	</form>
  </body>
</html>

页面显示这样子的，鼠标在验证码图片上点一下，验证码就变一下