使用方法：
项目中导入kaptcha-2.3.jar包在web.xml里面新增：<!– 登陆验证码Kaptcha –>
<servlet>
<servlet-name>Kaptcha</servlet-name>
<servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
<init-param>
<param-name>kaptcha.producer.impl</param-name>
<param-value>com.google.code.kaptcha.impl.DefaultKaptcha </param-value>
</init-param>
<init-param>
<param-name>kaptcha.textproducer.font.color</param-name>
<param-value>black</param-value>
</init-param>
<init-param>
<param-name>kaptcha.textproducer.char.space</param-name>
<param-value>10</param-value>
</init-param>
<init-param>
<param-name>kaptcha.border</param-name>
<param-value>no</param-value>
</init-param>
<init-param>
<param-name>kaptcha.border.thickness</param-name>
<param-value>0</param-value>
</init-param>
<init-param>
<param-name>kaptcha.textproducer.font.size</param-name>
<param-value>35</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.image.width</param-name>
<param-value>150</param-value>
</init-param>
<init-param>
<param-name>kaptcha.image.height</param-name>
<param-value>50</param-value>
</init-param>
<init-param>
上帝从不埋怨人们的愚昧，人们却埋怨上帝的不公
