How to use kaptcha to implement verification code in SpringBoot

<!-- 验证码-->
<dependency>
 <groupId>com.github.penggle</groupId>
 <artifactId>kaptcha</artifactId>
 <version>2.3.2</version>
</dependency>

@Configuration
public class kaptchaConfig {
  @Bean(name="captchaProducer")
  public DefaultKaptcha getKaptchaBean(){
    DefaultKaptcha defaultKaptcha=new DefaultKaptcha();
    Properties properties=new Properties();
    properties.setProperty("kaptcha.border", "yes");
    properties.setProperty("kaptcha.border.color", "105,179,90");
    properties.setProperty("kaptcha.textproducer.font.color", "blue");
    properties.setProperty("kaptcha.image.width", "125");
    properties.setProperty("kaptcha.image.height", "45");
    properties.setProperty("kaptcha.session.key", "code");
    properties.setProperty("kaptcha.textproducer.char.length", "4");
    properties.setProperty("kaptcha.textproducer.font.names", "宋体,楷体,微软雅黑");
    Config config=new Config(properties);
    defaultKaptcha.setConfig(config);
    return defaultKaptcha;
  }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
  <bean id="captchaProducer" class="com.google.code.kaptcha.impl.DefaultKaptcha">
    <property name="config">
      <bean class="com.google.code.kaptcha.util.Config">
        <constructor-arg type="java.util.Properties">
          <props>
            <prop key = "kaptcha.border ">yes</prop>
            <prop key="kaptcha.border.color">105,179,90</prop>
            <prop key="kaptcha.textproducer.font.color">blue</prop>
            <prop key="kaptcha.image.width">100</prop>
            <prop key="kaptcha.image.height">50</prop>
            <prop key="kaptcha.textproducer.font.size">27</prop>
            <prop key="kaptcha.session.key">code</prop>
            <prop key="kaptcha.textproducer.char.length">4</prop>
            <prop key="kaptcha.textproducer.font.names">宋体,楷体,微软雅黑</prop>
            <prop key="kaptcha.textproducer.char.string">23456789ABCEFGHJKMNOPQRSTUVWXYZ</prop>
            <prop key="kaptcha.obscurificator.impl">com.google.code.kaptcha.impl.WaterRipple</prop>
            <prop key="kaptcha.noise.color">black</prop>
            <prop key="kaptcha.noise.impl">com.google.code.kaptcha.impl.NoNoise</prop>
            <!--<prop key="kaptcha.noise.impl">com.google.code.kaptcha.impl.DefaultNoise</prop>-->
            <prop key="kaptcha.background.clear.from">185,56,213</prop>
            <prop key="kaptcha.background.clear.to">white</prop>
            <prop key="kaptcha.textproducer.char.space">3</prop>
          </props>
        </constructor-arg>
      </bean>
    </property>
  </bean>
</beans>

@EnableTransactionManagement// 启动注解事务管理，等同于xml配置方式的 <tx:annotation-driven />
@SpringBootApplication
@EnableScheduling//启动注解定时任务
@MapperScan(basePackages = "com.shawn.mapper")
@ImportResource(locations={"classpath:mykaptcha.xml"})
public class Application extends SpringBootServletInitializer {

  public static void main(String[] args) throws Exception {
    SpringApplication.run(Application.class, args);
  }

}

@CommonsLog
@Controller
public class KaptchaController extends BaseController {
  @Autowired
  private Producer captchaProducer;
  @GetMapping("/getKaptchaImage")
  public void getKaptchaImage() throws Exception {

    response.setDateHeader("Expires", 0);

    // Set standard HTTP/1.1 no-cache headers.
    response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
    // Set IE extended HTTP/1.1 no-cache headers (use addHeader).
    response.addHeader("Cache-Control", "post-check=0, pre-check=0");
    // Set standard HTTP/1.0 no-cache header.
    response.setHeader("Pragma", "no-cache");
    // return a jpeg
    response.setContentType("image/jpeg");
    // create the text for the image
    String capText = captchaProducer.createText();
    // store the text in the session
    //request.getSession().setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);
    //将验证码存到session
    session.setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);
    log.info(capText);
    // create the image with the text
    BufferedImage bi = captchaProducer.createImage(capText);
    ServletOutputStream out = response.getOutputStream();
    // write the data out
    ImageIO.write(bi, "jpg", out);
    try {
      out.flush();
    } finally {
      out.close();
    }
  }
}