<!-- 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>                             <param-name>kaptcha.background.clear.from</param-name>                             <param-value>255,255,255</param-value>                    </init-param>                    <init-param>                             <param-name>kaptcha.background.clear.to</param-name>                             <param-value>255,255,255</param-value>                    </init-param>                    <init-param>             <param-name>kaptcha.textproducer.char.string</param-name>             <param-value>0123456789</param-value>         </init-param>         <init-param>             <param-name>kaptcha.textproducer.font.names</param-name>             <param-value>Arial Black</param-value>         </init-param>          <init-param>             <param-name>kaptcha.noise.impl</param-name>             <param-value>com.google.code.kaptcha.impl.NoNoise</param-value>         </init-param>     </servlet>     <servlet-mapping>         <servlet-name>Kaptcha</servlet-name>         <url-pattern>/kaptcha.jpg</url-pattern> </servlet-mapping>

<img id="img" src="kaptcha.jpg" width="90" height="25" onclick="refresh();" alt="点击更换验证码"/> function refresh() {                   document.getElementById('img').src="kaptcha.jpg?"+Math.random(); }

request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);