·1.引入依赖

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

2.web.xml设置servlet

<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>

3.页面引用

<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>

4.后台获取生成的图片String值

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