验证码

kaptcha是一个非常实用的验证码生成工具，有了它，你可以生成各种样式的验证码，因为它是可配置的。

kaptcha工作的原理是调用com.google.code.kaptcha.servlet.KaptchaServlet，生成一个图片。同时将生成的验证码字符串放到HttpSession中。

kaptcha可以配置一下信息：

验证码的字体

验证码字体的大小

验证码字体的字体颜色

验证码内容的范围(数字，字母，中文汉字！)

验证码图片的大小，边框，边框粗细，边框颜色

验证码的干扰线(可以自己继承com.google.code.kaptcha.NoiseProducer写一个自定义的干扰线)

验证码的样式(鱼眼样式、3D、普通模糊……当然也可以继承com.google.code.kaptcha.GimpyEngine自定义样式)

……

详细信息请看下面的web.xml文件

下面介绍一下用法:

1.首先去官网下载jar:http://code.google.com/p/kaptcha/

2.建立一个web项目，导入kaptcha-2.3.jar到环境变量中。

3.配置web.xml文件

其实就是配置com.google.code.kaptcha.servlet.KaptchaServlet

  1 <?xml version="1.0" encoding="UTF-8"?>  
  2 <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
  3     xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"  
  4     version="2.4">  
  5     <servlet>  
  6         <servlet-name>Kaptcha</servlet-name>  
  7         <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>  
  8         <init-param>  
  9             <description> Border around kaptcha. Legal values are yes or no. </description>  
 10             <param-name>kaptcha.border</param-name>  
 11             <param-value>no</param-value>  
 12         </init-param>  
 13         <init-param>  
 14             <description>Color of the border. Legal values are r,g,b (and optional alpha) or white,black,blue. </description>  
 15             <param-name>kaptcha.border.color</param-name>  
 16             <param-value>red</param-value>  
 17         </init-param>  
 18         <init-param>  
 19             <description>Thickness of the border around kaptcha. Legal values are > 0. </description>  
 20             <param-name>kaptcha.border.thickness</param-name>  
 21             <param-value>5</param-value>  
 22         </init-param>  
 23         <init-param>  
 24             <description>Width in pixels of the kaptcha image. </description>  
 25             <param-name>kaptcha.image.width</param-name>  
 26             <param-value>80</param-value>  
 27         </init-param>  
 28         <init-param>  
 29             <description>Height in pixels of the kaptcha image. </description>  
 30             <param-name>kaptcha.image.height</param-name>  
 31             <param-value>40</param-value>  
 32         </init-param>  
 33         <init-param>  
 34             <description>The image producer. </description>  
 35             <param-name>kaptcha.producer.impl</param-name>  
 36             <param-value>com.google.code.kaptcha.impl.DefaultKaptcha </param-value>  
 37         </init-param>  
 38         <init-param>  
 39             <description>The text producer. </description>  
 40             <param-name>kaptcha.textproducer.impl</param-name>  
 41             <param-value>com.google.code.kaptcha.text.impl.DefaultTextCreator</param-value>  
 42         </init-param>  
 43         <init-param>  
 44             <description>The characters that will create the kaptcha. </description>  
 45             <param-name>kaptcha.textproducer.char.string</param-name>  
 46             <param-value>abcde2345678gfynmnpwx </param-value>  
 47         </init-param>  
 48         <init-param>  
 49             <description>The number of characters to display. </description>  
 50             <param-name>kaptcha.textproducer.char.length</param-name>  
 51             <param-value>5</param-value>  
 52         </init-param>  
 53         <init-param>  
 54             <description>A list of comma separated font names.</description>  
 55             <param-name>kaptcha.textproducer.font.names</param-name>  
 56             <param-value>Arial, Courier</param-value>  
 57         </init-param>  
 58         <init-param>  
 59             <description>The size of the font to use. </description>  
 60             <param-name>kaptcha.textproducer.font.size</param-name>  
 61             <param-value>23</param-value>  
 62         </init-param>  
 63         <init-param>  
 64             <description>The color to use for the font. Legal values are r,g,b. </description>  
 65             <param-name>kaptcha.textproducer.font.color</param-name>  
 66             <param-value>black</param-value>  
 67         </init-param>  
 68         <init-param>  
 69             <description>The noise producer. </description>  
 70             <param-name>kaptcha.noise.impl</param-name>  
 71             <param-value>com.google.code.kaptcha.impl.NoNoise </param-value>  
 72         </init-param>  
 73         <init-param>  
 74             <description>The noise color. Legal values are r,g,b. </description>  
 75             <param-name>kaptcha.noise.color</param-name>  
 76             <param-value>black</param-value>  
 77         </init-param>  
 78         <init-param>  
 79             <description>The obscurificator implementation. </description>  
 80             <param-name>kaptcha.obscurificator.impl</param-name>  
 81             <param-value>com.google.code.kaptcha.impl.ShadowGimpy</param-value>  
 82         </init-param>  
 83         <init-param>  
 84             <description>The background implementation. </description>  
 85             <param-name>kaptcha.background.impl</param-name>  
 86             <param-value>com.google.code.kaptcha.impl.DefaultBackground</param-value>  
 87         </init-param>  
 88         <init-param>  
 89             <description>Ending background color. Legal values are r,g,b. </description>  
 90             <param-name>kaptcha.background.clear.to</param-name>  
 91             <param-value>white</param-value>  
 92         </init-param>  
 93         <init-param>  
 94             <description>The word renderer implementation. </description>  
 95             <param-name>kaptcha.word.impl</param-name>  
 96             <param-value>com.google.code.kaptcha.text.impl.DefaultWordRenderer</param-value>  
 97         </init-param>  
 98         <init-param>  
 99             <description>The value for the kaptcha is generated and is put into the HttpSession. This is the key value for that item in the session. </description>  
100             <param-name>kaptcha.session.key</param-name>  
101             <param-value>KAPTCHA_SESSION_KEY</param-value>  
102         </init-param>  
103         <init-param>  
104             <description>The date the kaptcha is generated is put into the HttpSession. This is the key value for that item in the session. </description>  
105             <param-name>kaptcha.session.date</param-name>  
106             <param-value>KAPTCHA_SESSION_DATE</param-value>  
107         </init-param>  
108     </servlet>  
109     <servlet-mapping>  
110         <servlet-name>Kaptcha</servlet-name>  
111         <url-pattern>/Kaptcha.jpg</url-pattern>  
112     </servlet-mapping>  
113     <welcome-file-list>  
114         <welcome-file>KaptchaExample.jsp</welcome-file>  
115     </welcome-file-list>  
116 </web-app>

View Code

4.编写KaptchaExample.jsp

这里用到了jQuery，所以添加了jQuery的库

 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">  
 2 <html>  
 3     <head>  
 4         <%@ page language="java" contentType="text/html; charset=UTF-8"%>  
 5         <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">  
 6         <title>Kaptcha Example</title>  
 7         <mce:script type="text/javascript" src="js/jquery-1.3.2.js" mce_src="js/jquery-1.3.2.js"></mce:script>  
 8     </head>  
 9     <body>  
10         Enter in the  
11         <a href="http://code.google.com/p/kaptcha/" mce_href="http://code.google.com/p/kaptcha/">Kaptcha</a> to see if it  
12         matches what is stored in the session attributes.  
13         <table>  
14             <tr>  
15                 <td>  
16                     <img src="Kaptcha.jpg" mce_src="Kaptcha.jpg" id="kaptchaImage" />  
17                     <mce:script type="text/javascript"><!--  
18 $('#kaptchaImage').click(  
19         function() {  
20             $(this).hide().attr('src',  
21                     'Kaptcha.jpg?' + Math.floor(Math.random() * 100)).fadeIn();  
22         })  
23 // --></mce:script>  
24                     <br />  
25                     单击换图片  
26                 </td>  
27                 <td valign="top">  
28                     <form method="POST">  
29                         <br>  
30                         验证码::  
31                         <input type="text" name="kaptchafield">  
32                         <br />  
33                         <input type="submit" name="submit">  
34                     </form>  
35                 </td>  
36             </tr>  
37         </table>  
38         <br />  
39         <br />  
40         <br />  
41         <br />  
42         <%  
43             String c = (String) session  
44                     .getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);  
45             String parm = (String) request.getParameter("kaptchafield");  
46               
47             System.out.println(c);  
48             out.println("Parameter: " + parm + " ? Session Key: " + c + " : ");  
49             if (c != null && parm != null)  
50             {  
51                 if (c.equals(parm))  
52                 {  
53                     out.println("<b>true</b>");  
54                 } else  
55                 {  
56                     out.println("<b>false</b>");  
57                 }  
58             }  
59         %>  
60     </body>  
61 </html>

View Code

参考文献：

http://blog.csdn.net/ol_beta/article/details/5877630

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原文地址：https://www.cnblogs.com/dobestself-994395/p/4294426.html