kaptcha开源验证码

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)

    <?xml version="1.0" encoding="UTF-8"?>  
    <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"  
        version="2.4">  
        <servlet>  
            <servlet-name>Kaptcha</servlet-name>  
            <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>  
            <init-param>  
                <description> Border around kaptcha. Legal values are yes or no. </description>  
                <param-name>kaptcha.border</param-name>  
                <param-value>no</param-value>  
            </init-param>  
            <init-param>  
                <description>Color of the border. Legal values are r,g,b (and optional alpha) or white,black,blue. </description>  
                <param-name>kaptcha.border.color</param-name>  
                <param-value>red</param-value>  
            </init-param>  
            <init-param>  
                <description>Thickness of the border around kaptcha. Legal values are > 0. </description>  
                <param-name>kaptcha.border.thickness</param-name>  
                <param-value>5</param-value>  
            </init-param>  
            <init-param>  
                <description>Width in pixels of the kaptcha image. </description>  
                <param-name>kaptcha.image.width</param-name>  
                <param-value>80</param-value>  
            </init-param>  
            <init-param>  
                <description>Height in pixels of the kaptcha image. </description>  
                <param-name>kaptcha.image.height</param-name>  
                <param-value>40</param-value>  
            </init-param>  
            <init-param>  
                <description>The image producer. </description>  
                <param-name>kaptcha.producer.impl</param-name>  
                <param-value>com.google.code.kaptcha.impl.DefaultKaptcha </param-value>  
            </init-param>  
            <init-param>  
                <description>The text producer. </description>  
                <param-name>kaptcha.textproducer.impl</param-name>  
                <param-value>com.google.code.kaptcha.text.impl.DefaultTextCreator</param-value>  
            </init-param>  
            <init-param>  
                <description>The characters that will create the kaptcha. </description>  
                <param-name>kaptcha.textproducer.char.string</param-name>  
                <param-value>abcde2345678gfynmnpwx </param-value>  
            </init-param>  
            <init-param>  
                <description>The number of characters to display. </description>  
                <param-name>kaptcha.textproducer.char.length</param-name>  
                <param-value>5</param-value>  
            </init-param>  
            <init-param>  
                <description>A list of comma separated font names.</description>  
                <param-name>kaptcha.textproducer.font.names</param-name>  
                <param-value>Arial, Courier</param-value>  
            </init-param>  
            <init-param>  
                <description>The size of the font to use. </description>  
                <param-name>kaptcha.textproducer.font.size</param-name>  
                <param-value>23</param-value>  
            </init-param>  
            <init-param>  
                <description>The color to use for the font. Legal values are r,g,b. </description>  
                <param-name>kaptcha.textproducer.font.color</param-name>  
                <param-value>black</param-value>  
            </init-param>  
            <init-param>  
                <description>The noise producer. </description>  
                <param-name>kaptcha.noise.impl</param-name>  
                <param-value>com.google.code.kaptcha.impl.NoNoise </param-value>  
            </init-param>  
            <init-param>  
                <description>The noise color. Legal values are r,g,b. </description>  
                <param-name>kaptcha.noise.color</param-name>  
                <param-value>black</param-value>  
            </init-param>  
            <init-param>  
                <description>The obscurificator implementation. </description>  
                <param-name>kaptcha.obscurificator.impl</param-name>  
                <param-value>com.google.code.kaptcha.impl.ShadowGimpy</param-value>  
            </init-param>  
            <init-param>  
                <description>The background implementation. </description>  
                <param-name>kaptcha.background.impl</param-name>  
                <param-value>com.google.code.kaptcha.impl.DefaultBackground</param-value>  
            </init-param>  
            <init-param>  
                <description>Ending background color. Legal values are r,g,b. </description>  
                <param-name>kaptcha.background.clear.to</param-name>  
                <param-value>white</param-value>  
            </init-param>  
            <init-param>  
                <description>The word renderer implementation. </description>  
                <param-name>kaptcha.word.impl</param-name>  
                <param-value>com.google.code.kaptcha.text.impl.DefaultWordRenderer</param-value>  
            </init-param>  
            <init-param>  
                <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>  
                <param-name>kaptcha.session.key</param-name>  
                <param-value>KAPTCHA_SESSION_KEY</param-value>  
            </init-param>  
            <init-param>  
                <description>The date the kaptcha is generated is put into the HttpSession. This is the key value for that item in the session. </description>  
                <param-name>kaptcha.session.date</param-name>  
                <param-value>KAPTCHA_SESSION_DATE</param-value>  
            </init-param>  
        </servlet>  
        <servlet-mapping>  
            <servlet-name>Kaptcha</servlet-name>  
            <url-pattern>/Kaptcha.jpg</url-pattern>  
        </servlet-mapping>  
        <welcome-file-list>  
            <welcome-file>KaptchaExample.jsp</welcome-file>  
        </welcome-file-list>  
    </web-app>  

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