1.在pom中引入依赖
<dependency>
<groupId>com.github.penggle</groupId>
<artifactId>kaptcha</artifactId>
<version>2.3.2</version>
</dependency>
2.在web.xml中配置其对于的Servelet 设置以及相应的servlet-mapping
<servlet>
<servlet-name>Kaptcha</servlet-name>
<servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
<!-- 是否有边框-->
<init-param>
<param-name>kaptcha.border</param-name>
<param-value>no</param-value>
</init-param>
<!-- 字体颜色-->
<init-param>
<param-name>kaptcha.textproducer.font.color</param-name>
<param-value>red</param-value>
</init-param>
<!-- 图片宽带-->
<init-param>
<param-name>kaptcha.image.width</param-name>
<param-value>135</param-value>
</init-param>
<!-- 使用那些字符生成验证码-->
<init-param>
<param-name>kaptcha.textproducer.char.string</param-name>
<param-value>ABCDEFGHIJKLMNOPQRST345679</param-value>
</init-param>
<!-- 图片高度-->
<init-param>
<param-name>kaptcha.image.height</param-name>
<param-value>50</param-value>
</init-param>
<!-- 字体大小-->
<init-param>
<param-name>kaptcha.textproducer.font.size</param-name>
<param-value>43</param-value>
</init-param>
<!-- 干扰线颜色-->
<init-param>
<param-name>kaptcha.noise.color</param-name>
<param-value>black</param-value>
</init-param>
<!--验证码字符个数-->
<init-param>
<param-name>kaptcha.textproducer.char.length</param-name>
<param-value>4</param-value>
</init-param>
<!-- 字体-->
<init-param>
<param-name>kaptcha.textproducer.font.names</param-name>
<param-value>Arial</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Kaptcha</servlet-name>
<url-pattern>/Kaptcha</url-pattern>
</servlet-mapping>
3.前端html页面部分
当刚进入页面时 验证码图片部分调用web.xml中的Kaptcha Servelet（src=“../Kaptcha”）
当发生点击事件时会调用changeVerifyCode(this)的方法
注：调用changeVerifyCode(this) 时路径要生成随机四位数
4.将前端获取的实际输入验证码传入后台与Kaptcha图片验证码进行匹配
public class CodeUtil { public static boolean checkVerifyCode(HttpServletRequest request){ String verifyCodeExpected=(String)request.getSession().getAttribute( Constants.KAPTCHA_SESSION_KEY); String verifyCodeActual=HttpServletRequestUtil.getString(request,"verifyCodeActual"); if (!verifyCodeActual.equals(verifyCodeExpected)||verifyCodeActual==null){ return false; }else return true; } }
原文：https://www.cnblogs.com/Mr-BING/p/10484335.html