<dependency><groupId>com.github.penggle</groupId><artifactId>kaptcha</artifactId><version>2.3.2</version></dependency>

<!--配置Kaptcha--><beanid="kaptchaProducer"class="com.google.code.kaptcha.impl.DefaultKaptcha"><propertyname="config"><beanclass="com.google.code.kaptcha.util.Config"><constructor-arg><props><!--验证码图片不生成边框--><propkey="kaptcha.border">no</prop><!--验证码图片宽度为120像素--><propkey="kaptcha.image.width">120</prop><!--验证码图片字体颜色为蓝色--><propkey="kaptcha.textproducer.font.color">blue</prop><!--每个字符最大占用40像素--><propkey="kaptcha.textproducer.font.size">40</prop><!--验证码包含4个字符--><propkey="kaptcha.textproducer.char.length">4</prop></props></constructor-arg></bean></property></bean>

@ControllerpublicclassKaptchaController {
@ResourceprivateProducerkaptchaProducer;
@GetMapping("/api/verify_code")
publicvoidcreateVerifyCode(HttpServletRequestrequest , HttpServletResponseresponse) throwsIOException {
//响应立即过期(通知浏览器让缓存立即失效，否则会导致无法刷新验证码)response.setDateHeader("Expires" , 0);
//不缓存任何图片数据response.setHeader("Cache-Control" , "no-store,no-cache,must-revalidate");
response.setHeader("Cache-Control" ,"post-check=0,pre-check=0");
response.setHeader("Pragma" , "no-cache");
response.setContentType("image/png");
//生成验证码图片Stringtext=kaptchaProducer.createText();
request.getSession().setAttribute("kaptchaVerifyCode" , text);
BufferedImageimage=kaptchaProducer.createImage(text);
ServletOutputStreamoutputStream=response.getOutputStream();
ImageIO.write(image, "png", outputStream);
outputStream.flush();//对客户端输出outputStream.close();
    }
}