Kaptcha验证码使用

<dependency>
<groupId>com.github.axet</groupId>
<artifactId>kaptcha</artifactId>
<version>0.0.9</version>
</dependency>

<servlet>
<servlet-name>Kaptcha</servlet-name>
<servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Kaptcha</servlet-name>
<url-pattern>/kaptcha.jpg</url-pattern>
</servlet-mapping>

<form action="/user/login" method="post">
<img src="kaptcha.jpg" id="kaptchaImage" />
<input type="text" name="captcha" value="" /><br/>
<input type="submit" name="submit" value="submit" />
</form>

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