kaptcha 验证码组件使用简介

使用方法：
1、到http://code.google.com/p/kaptcha/ 下载jar文件到 WEB-INF/lib目录下
2、在web.xml中配置servlet：
<servlet>

<servlet-name>Kaptcha</servlet-name>

<servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>

<init-param>

<param-name>kaptcha.image.width</param-name>

<param-value>65</param-value>

</init-param>

<init-param>

<param-name>kaptcha.image.height</param-name>

<param-value>30</param-value>

</init-param>

<init-param>

<param-name>kaptcha.textproducer.char.length</param-name>

<param-value>4</param-value>

</init-param>

<init-param>

<param-name>kaptcha.textproducer.font.size</param-name>

<param-value>25</param-value>

</init-param>

<init-param>

<param-name>kaptcha.obscurificator.impl</param-name>

<param-value>com.google.code.kaptcha.impl.ShadowGimpy</param-value>

</init-param>

</servlet>
<servlet-mapping>

<servlet-name>Kaptcha</servlet-name>

<url-pattern>/kaptcha.jpg</url-pattern>

</servlet-mapping>

如果需要全部数字

<init-param>

<param-name>kaptcha.textproducer.char.string</param-name>

<param-value>0123456789</param-value>

</init-param>

去掉干扰线

<init-param>

<param-name>kaptcha.noise.impl</param-name>

<param-value>com.google.code.kaptcha.impl.NoNoise </param-value>

</init-param>
3.html中添加代码：
<img src="kaptcha.jpg" />
4.Java中获取真实的验证码：
String kaptchaExpected = (String)request.getSession().getAttribute (com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);