java web验证码功能实现

<servlet> <!-- 验证码功能 --> <servlet-name>KaptchaServlet</servlet-name> <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class> <init-param> <!-- 定义是否存在有边框 --> <param-name>kaptcha.border</param-name> <param-value>no</param-value> </init-param> <init-param> <!-- 定义边框颜色 --> <param-name>kaptcha.border.color</param-name> <param-value>105,179,90</param-value> </init-param> <init-param> <!-- 设置字体颜色 --> <param-name>kaptcha.textproducer.font.color</param-name> <param-value>red</param-value> </init-param> <init-param> <!-- 设置生成图片宽度 --> <param-name>kaptcha.image.width</param-name> <param-value>130</param-value> </init-param> <init-param> <!-- 设置生成图片高度 --> <param-name>kaptcha.image.height</param-name> <param-value>38</param-value> </init-param> <init-param> <!-- 设置验证码显示文字尺寸 --> <param-name>kaptcha.textproducer.font.size</param-name> <param-value>30</param-value> </init-param> <init-param> <!-- 设置验证码保存到session中的属性名称 --> <param-name>kaptcha.session.key</param-name> <param-value>rand</param-value> </init-param> <init-param> <!-- 设置字符间距 --> <param-name>kaptcha.textproducer.char.space</param-name> <param-value>2</param-value> </init-param> <init-param> <!-- 设置生成的验证码长度 --> <param-name>kaptcha.textproducer.char.length</param-name> <param-value>4</param-value> </init-param> <init-param> <!-- 设置使用的字体 --> <param-name>kaptcha.textproducer.font.names</param-name> <param-value>宋体,楷体,微软雅黑</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>KaptchaServlet</servlet-name> <url-pattern>/captcha.jpg</url-pattern> </servlet-mapping>