验证码 Demo

 1         //设置响应头
 2         response.setCharacterEncoding("image/jpeg");
 3         int width=160;
 4         int height=40;
 5         BufferedImage image=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
 6         Graphics g=image.getGraphics();
 7         Graphics2D g2d = (Graphics2D) g;
 8         g2d.setColor(Color.WHITE);
 9         g2d.fillRect(0, 0, width, height);
10         g2d.setFont(new Font("宋体", Font.BOLD, 18));
11          Random random=new Random();
12         for(int i=0;i<4;i++)//获取随机四个汉字
13         {
14             Color c=new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256));
15             String s=GetStr();
16
17             AffineTransform aff = new AffineTransform();
18             aff.rotate(Math.random(),i*10,height-20);//旋转
19             aff.scale(0.2+Math.random(), 0.2+Math.random());//缩放
20             g2d.setTransform(aff);
21             System.err.println(">:"+s);
22
23             g2d.setColor(c);
24             g2d.drawString(s, i*10, height- 5);
25         }
26
27         for(int i=0;i<3;i++)    //干扰线
28         {
29             Color c=new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256));
30             g2d.setColor(c);
31             g2d.drawLine(random.nextInt(width), random.nextInt(height), random.nextInt(width), random.nextInt(height));
32
33         }
34         g2d.dispose();//图片生效
35         ImageIO.write(image, "jpeg", response.getOutputStream());//输出
36         System.out.println("输出");
37     }
38
39     //获取汉字
40     private static String GetStr()
41     {
42         String str = null;
43         try {
44
45             int hightPos, lowPos; // 定义高低位
46             Random random = new Random();
47             hightPos = (176 + Math.abs(random.nextInt(39)));//获取高位值
48             lowPos = (161 + Math.abs(random.nextInt(93)));//获取低位值
49             byte[] b = new byte[2];
50             b[0] = (new Integer(hightPos).byteValue());
51             b[1] = (new Integer(lowPos).byteValue());
52             str = new String(b, "GBK");//转成中文
53
54         } catch (Exception e) {
55             e.printStackTrace();
56         }
57         return str;
58
59     }

PS：写验证码不能把所有的都用上，这样就无法识别了，可以选择其中的几种进行，如写汉字只加干扰线，写字母加旋转等。