java Web图片验证码

1. 1.在body中加入如下代码：  
2. <script language="javascript">  
3.     function changeCode() {  
4.         document.getElementById('checkImg').src = 'GetCaptcha?temp='+ (new Date().getTime().toString(36));  
5.         return false;  
6.     }  
7. </script>  
8.   
9. <center>  
10.         <form>  
11.             验证码: <input type="text" maxlength="113" οnmοuseοver="this.style.background='pink'" οnmοuseοut="this.style.background='white'">  
12.              <img src="GetCaptcha" alt="验证码" name="checkImg" id="checkImg" onClick="changeCode()" />  
13.         </form>  
14.     </center>  
15.   
16. 2.在web.xml中配置如下代码：  
17.     <servlet>  
18.         <servlet-name>GetCaptcha</servlet-name>  
19.         <servlet-class>com.eims.util.GetCaptcha</servlet-class>  
20.     </servlet>  
21.   
22.   
23.     <servlet-mapping>  
24.         <servlet-name>GetCaptcha</servlet-name>  
25.         <url-pattern>/GetCaptcha</url-pattern>  
26.     </servlet-mapping>  
27.   
28. 3.在com.eims.util.GetCaptcha包中加入如下工具类  
29.     package com.eims.util;  
30.   
31.   
32. import java.io.IOException;    
33. import javax.servlet.ServletException;    
34. import javax.servlet.http.HttpServlet;    
35. import javax.servlet.http.HttpServletRequest;    
36. import javax.servlet.http.HttpServletResponse;    
37. import javax.servlet.http.HttpSession;    
38. import java.util.*;    
39. import java.awt.*;    
40. import java.awt.image.*;    
41.     
42. import javax.imageio.*;    
43. /** 
44.  *  
45.  * @author mzba 
46.  * 
47.  */  
48. public class GetCaptcha extends HttpServlet {    
49.     private static final long serialVersionUID = 1L;    
50.     
51.     /**  
52.      * @see HttpServlet#HttpServlet()  
53.      */    
54.     public GetCaptcha() {    
55.         super();    
56.         // TODO Auto-generated constructor stub    
57.     }    
58.     
59.     /**  
60.      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse  
61.      *      response)  
62.      */    
63.     protected void doGet(HttpServletRequest request,    
64.             HttpServletResponse response) throws ServletException, IOException {    
65.         response.setContentType("image/jpeg");    
66.         response.setHeader("Pragma", "No-cache");    
67.         response.setHeader("Cache-Control", "no-cache");    
68.         response.setDateHeader("Expires", 0);    
69.         HttpSession session = request.getSession();    
70.         int width = 75, height = 25;    
71.         BufferedImage image = new BufferedImage(width, height,    
72.                 BufferedImage.TYPE_INT_RGB);    
73.   
74.   
75.         Graphics g = image.getGraphics();    
76.         Random random = new Random();    
77.         g.setColor(getRandColor(200, 250));    
78.         g.fillRect(0, 0, width, height);    
79.         g.setFont(new Font("Times New Roman", Font.PLAIN, 24));    
80.         g.setColor(getRandColor(160, 200));    
81.         g.drawRect(0, 0, width - 1, height - 1);    
82.         g.setColor(getRandColor(160, 200));    
83.         for (int i = 0; i < 155; i++) {    
84.             int x = random.nextInt(width);    
85.             int y = random.nextInt(height);    
86.             int xl = random.nextInt(12);    
87.             int yl = random.nextInt(12);    
88.             g.drawLine(x, y, x + xl, y + yl);    
89.         }    
90.         String sRand = "";    
91.         for (int i = 0; i < 4; i++) {    
92.             String rand = String.valueOf(random.nextInt(10));    
93.             sRand += rand;    
94.             g.setColor(new Color(20 + random.nextInt(110), 20 + random    
95.                     .nextInt(110), 20 + random.nextInt(110)));    
96.             g.drawString(rand, 13 * i + 14, 20);    
97.         }    
98.     
99.         session.setAttribute("vcode", sRand);    
100.     
101.         g.dispose();    
102.         ImageIO.write(image, "JPEG", response.getOutputStream());    
103.     }    
104.     
105.     /**  
106.      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse  
107.      *      response)  
108.      */    
109.     protected void doPost(HttpServletRequest request,    
110.             HttpServletResponse response) throws ServletException, IOException {    
111.         // TODO Auto-generated method stub    
112.     }    
113.     
114.     Color getRandColor(int fc, int bc) {  
115.         Random random = new Random();    
116.         if (fc > 255)    
117.             fc = 255;    
118.         if (bc > 255)    
119.             bc = 255;    
120.         int r = fc + random.nextInt(bc - fc);    
121.         int g = fc + random.nextInt(bc - fc);    
122.         int b = fc + random.nextInt(bc - fc);    
123.         return new Color(r, g, b);    
124.     }    
125.     
126. }    
127.   
128. 4.在servlet中使用如下代码进行验证：  
129.         /** 
130.      * 验证用户输入的验证码输入的是否正确 
131.      * @param request 
132.      * @param response 
133.      * @throws ServletException 
134.      * @throws IOException 
135.      */  
136.     public boolean checkValidationCode(HttpServletRequest request, HttpServletResponse response)  
137.             throws ServletException, IOException {  
138.         boolean flag=true;  
139.         HttpSession session=request.getSession();  
140.         String validationRightCode=(String)session.getAttribute("vcode");  
141.         String validationUserCode=request.getParameter("validationCode");  
142.         if(!validationRightCode.equals(validationUserCode)){  
143.             request.setAttribute("information","验证码输入不正确！");  
144.             flag=false;  
145.             RequestDispatcher rd=request.getRequestDispatcher("login/dealwith.jsp");  
146.             rd.forward(request, response);  
147.         }  
148.         return flag;  
149.     }