验证码的实现

 1 　　　　//js函数
 2 　　　　function _hyz()//换一张函数JS代码
 3        {
 4          /*
 5          1. 获取<img>元素
 6          2. 给它的src指向/tools/VerifyCodeServlet
 7          */
 8          var img=document.getElementById("imgVerifyCode");
 9          //需要给出一个参数，这个参数每次都不同，这样才能刷新浏览器缓存！
10          img.src = "/tools/VerifyCodeServlet?a="+ new Date().getTime();
11        }

12 　　　　 //jsp中代码
13 　　　　 验证码:<input type="text" name="verifyCode"/><br>  
14 　　　　 <img src="/tools/VerifyCodeServlet" id="imgVerifyCode"/>
15  　　　　<a href="javascript:_hyz()">换一张</a><br>
16    
　
　　　　//servlet中使用验证码代码
17 　　public String login(HttpServletRequest request, HttpServletResponse response)
18             throws ServletException, IOException {
19         /*
20          * 校验验证码
21          *   1.获取表单中的验证码
22          *   2.获取图片上的文字
23          */
24         String verifyCode =request.getParameter("verifyCode");
25         //VerifyCodeServlet会把真正的验证码保存到session中
26         String vcode =(String) request.getSession().getAttribute("vCode");//
27  
28         System.out.println(vcode+"  "+verifyCode);
29         System.out.println(verifyCode.equalsIgnoreCase(vcode));//不区分大小写比较
30  
31         return null;
32     }

 1 //生成验证码的过程JAVA代码,这个在网上有很多，也可以自己随自己的需求设计。
 2 public class VerifyCode {
 3     private int w = 70;
 4     private int h = 35;
 5      private Random r = new Random();
 6      // 验证码中字体、数字、字母和背景颜色
 7     private String[] fontNames  = {"宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312"};
 8     private String codes  = "23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";
 9     private Color bgColor  = new Color(255, 255, 255);
10     private String text ;
11  
12     private Color randomColor () {
13         int red = r.nextInt(150);
14         int green = r.nextInt(150);
15         int blue = r.nextInt(150);
16         return new Color(red, green, blue);
17     }
18  
19     private Font randomFont () {
20         int index = r.nextInt(fontNames.length);
21         String fontName = fontNames[index];
22         int style = r.nextInt(4);
23         int size = r.nextInt(5) + 24; 
24         return new Font(fontName, style, size);
25     }
26  
27     private void drawLine (BufferedImage image) {
28         int num  = 3;
29         Graphics2D g2 = (Graphics2D)image.getGraphics();
30         for(int i = 0; i < num; i++) {
31             int x1 = r.nextInt(w);
32             int y1 = r.nextInt(h);
33             int x2 = r.nextInt(w);
34             int y2 = r.nextInt(h); 
35             g2.setStroke(new BasicStroke(1.5F)); 
36             g2.setColor(Color.BLUE); 
37             g2.drawLine(x1, y1, x2, y2);
38         }
39     }
40  
41     private char randomChar () {
42         int index = r.nextInt(codes.length());
43         return codes.charAt(index);
44     }
45  
46     private BufferedImage createImage () {
47         BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); 
48         Graphics2D g2 = (Graphics2D)image.getGraphics(); 
49         g2.setColor(this.bgColor);
50         g2.fillRect(0, 0, w, h);
51          return image;
52     }
53  
54     public BufferedImage getImage () {
55         BufferedImage image = createImage(); 
56         Graphics2D g2 = (Graphics2D)image.getGraphics();
57         StringBuilder sb = new StringBuilder();
58         // 向图片中画4个字符
59         for(int i = 0; i < 4; i++)  {
60             String s = randomChar() + ""; 
61             sb.append(s); 
62             float x = i * 1.0F * w / 4; 
63             g2.setFont(randomFont()); 
64             g2.setColor(randomColor()); 
65             g2.drawString(s, x, h-5); 
66         }
67         this.text = sb.toString(); 
68         drawLine(image); 
69         return image;        
70     }
71  
72     public String getText () {
73         return text;
74     }
75  
76     public static void output (BufferedImage image, OutputStream out) 
77                 throws IOException {
78         ImageIO.write(image, "JPEG", out);
79     }
80 public void doGet(HttpServletRequest request, HttpServletResponse response)
81             throws ServletException, IOException {
82         VerifyCode vc = new VerifyCode();
83         BufferedImage image = vc.getImage();//获取一次性验证码图片
84         //该方法必须在getImage()方法之后来调用
85 　　  //System.out.println(vc.getText());//获取图片上的文本
86         VerifyCode.output(image, response.getOutputStream());//把图片写到指定流中
87         // 把文本保存到session中，为LoginServlet验证做准备
88         request.getSession().setAttribute("vCode", vc.getText());
89     }