1，maven配置
<dependency>
<groupId>com.google.code</groupId>
<artifactId>kaptcha</artifactId>
<version>2.3.2</version>
</dependency>
2,web.xml配置servlet拦截
<servlet>
<servlet-name>kaptcha</servlet-name>
<servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
<init-param>
<param-name>kaptcha.border</param-name>
<param-value>no</param-value>
</init-param>
<init-param>
<param-name>kaptcha.border.color</param-name>
<param-value>red</param-value>
</init-param>
<init-param>
<param-name>kaptcha.border.thickness</param-name>
<param-value>5</param-value>
</init-param>
<init-param>
<param-name>kaptcha.image.width</param-name>
<param-value>85</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.space</param-name>
<param-value>5</param-value>
</init-param>
<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.impl</param-name>
<param-value>com.google.code.kaptcha.text.impl.DefaultTextCreator</param-value>
</init-param>
<init-param>
<param-name>kaptcha.textproducer.char.string</param-name>
<param-value>1234567890</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.names</param-name>
<param-value>Consolas,Arial, Courier</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.textproducer.font.color</param-name>
<param-value>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>
<init-param>
<param-name>kaptcha.noise.color</param-name>
<param-value>black</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>
<init-param>
<param-name>kaptcha.background.impl</param-name>
<param-value>com.google.code.kaptcha.impl.DefaultBackground</param-value>
</init-param>
<init-param>
<param-name>kaptcha.background.clear.from</param-name>
<param-value>211,236,230</param-value>
</init-param>
<init-param>
<param-name>kaptcha.background.clear.to</param-name>
<param-value>211,237,228</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>kaptcha</servlet-name>
<url-pattern>/kaptcha.jpg</url-pattern>
</servlet-mapping>
3，页面html
<img id="img" width="140" height="45" src="kaptcha.jpg" >
<span ><a href="javascript:void(0);">看不清，换一张</a></span>
$("#img").hide().attr(‘src‘, ‘kaptcha.jpg?‘ + Math.floor(Math.random() * 100)).fadeIn();//刷新
4，从HttpServletRequest 中获取验证码
HttpSession session = request.getSession();
String captcha = (String) session
.getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);