<!-- https://mvnrepository.com/artifact/com.github.penggle/kaptcha --> 
<dependency> 
 <groupId>com.github.penggle</groupId> 
 <artifactId>kaptcha</artifactId> 
 <version>2.3.2</version> 
</dependency> 

<?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">0123456789ABCEFGHIJKLMNOPQRSTUVWXYZ</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.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> 

@SpringBootApplication 
@ImportResource(locations={"classpath:mykaptcha.xml"}) 
public class Application { 
 public static void main(String[] args) { 
  SpringApplication.run(Application.class, args); 
 } 
} 

@Autowired 
DefaultKaptcha defaultKaptcha; 
...... 
@RequestMapping("/defaultKaptcha") 
 public void defaultKaptcha(HttpServletRequest httpServletRequest,HttpServletResponse httpServletResponse) throws Exception{ 
   byte[] captchaChallengeAsJpeg = null; 
    ByteArrayOutputStream jpegOutputStream = new ByteArrayOutputStream(); 
    try { 
    //生产验证码字符串并保存到session中 
    String createText = defaultKaptcha.createText(); 
    httpServletRequest.getSession().setAttribute("vrifyCode", createText); 
    //使用生产的验证码字符串返回一个BufferedImage对象并转为byte写入到byte数组中 
    BufferedImage challenge = defaultKaptcha.createImage(createText); 
    ImageIO.write(challenge, "jpg", jpegOutputStream); 
    } catch (IllegalArgumentException e) { 
     httpServletResponse.sendError(HttpServletResponse.SC_NOT_FOUND); 
     return; 
    } 
    //定义response输出类型为image/jpeg类型，使用response输出流输出图片的byte数组 
    captchaChallengeAsJpeg = jpegOutputStream.toByteArray(); 
    httpServletResponse.setHeader("Cache-Control", "no-store"); 
    httpServletResponse.setHeader("Pragma", "no-cache"); 
    httpServletResponse.setDateHeader("Expires", 0); 
    httpServletResponse.setContentType("image/jpeg"); 
    ServletOutputStream responseOutputStream = 
      httpServletResponse.getOutputStream(); 
    responseOutputStream.write(captchaChallengeAsJpeg); 
    responseOutputStream.flush(); 
    responseOutputStream.close(); 
 } 

@RequestMapping("/imgvrifyControllerDefaultKaptcha") 
public ModelAndView imgvrifyControllerDefaultKaptcha(HttpServletRequest httpServletRequest,HttpServletResponse httpServletResponse){ 
 ModelAndView andView = new ModelAndView(); 
  String captchaId = (String) httpServletRequest.getSession().getAttribute("vrifyCode"); 
  String parameter = httpServletRequest.getParameter("vrifyCode"); 
  System.out.println("Session vrifyCode "+captchaId+" form vrifyCode "+parameter); 
  
 if (!captchaId.equals(parameter)) { 
  andView.addObject("info", "错误的验证码"); 
  andView.setViewName("index"); 
 } else { 
  andView.addObject("info", "登录成功"); 
  andView.setViewName("succeed"); 
   
 } 
 return andView; 
} 

<!DOCTYPE html> 
<html> 
<head lang="en"> 
 <meta charset="UTF-8" /> 
 <title>hello</title> 
</head> 
<body> 
 <h1 th:text="${info}" /> 
 <div> 
  <!-- <img alt="这是图片" src="/img/001.png"/> --> 
  <img alt="验证码" onclick = "this.src='/defaultKaptcha?d='+new Date()*1" src="/defaultKaptcha" /> 
 </div> 
 <form action="imgvrifyControllerDefaultKaptcha"> 
  <input type="text" name="vrifyCode" /> 
  <input type="submit" value="提交"></input> 
 </form> 
</body> 
</html> 

import java.util.Properties; 
import org.springframework.context.annotation.Bean; 
import org.springframework.stereotype.Component; 
import com.google.code.kaptcha.impl.DefaultKaptcha; 
import com.google.code.kaptcha.util.Config; 
@Component 
public class KaptchaConfig { 
 @Bean 
 public DefaultKaptcha getDefaultKaptcha(){ 
  com.google.code.kaptcha.impl.DefaultKaptcha defaultKaptcha = new com.google.code.kaptcha.impl.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", "110"); 
  properties.setProperty("kaptcha.image.height", "40"); 
  properties.setProperty("kaptcha.textproducer.font.size", "30"); 
  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; 
 } 
}