1 创建springboot工程

2 pom中引入相关依赖

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

3 三种实现方式

3.1 第一种使用xml文件配置属性

resources下新建kaptcha.xml

<?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>

启动类加入@ImportResource注解

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

com.xja.controller 包中创建测试controller

/**
 * 生成验证码并把验证码存储到session中
 */
@Controller
public class CodeController {
    @Autowired
    private Producer captchaProducer = null;
    @GetMapping("/kaptcha")
    public void getKaptchaImage(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HttpSession session = request.getSession();
        response.setDateHeader("Expires", 0);
        response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
        response.addHeader("Cache-Control", "post-check=0, pre-check=0");
        response.setHeader("Pragma", "no-cache");
        response.setContentType("image/jpeg");
        //生成验证码
        String capText = captchaProducer.createText();
        session.setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);
        //向客户端写出
        BufferedImage bi = captchaProducer.createImage(capText);
        ServletOutputStream out = response.getOutputStream();
        ImageIO.write(bi, "jpg", out);
        try {
            out.flush();
        } finally {
            out.close();
        }
    }
}

3.2 第二种使用配置bean配置属性

com.xja.config 下新建 KaptchaConfig

@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", "6");
        properties.setProperty("kaptcha.textproducer.font.names", "宋体,楷体,微软雅黑");
        Config config = new Config(properties);
        defaultKaptcha.setConfig(config);
        return defaultKaptcha;
    }
}

3.3 第三种使用配置bean，验证码属性使用验证码属性进行配置

建议使用第三种方法 resources下新建 kaptcha.properties

##### Kaptcha Information
kaptcha.width=150
kaptcha.height=42
kaptcha.border=no
kaptcha.textproducer.font.size=40
kaptcha.textproducer.char.space=10
kaptcha.textproducer.font.names=\u4EFF\u5B8B,\u5FAE\u8F6F\u96C5\u9ED1
kaptcha.textproducer.char.string=1234567890
kaptcha.textproducer.char.length=4
kaptcha.background.clear.from=92,189,170
kaptcha.background.clear.to=255,255,255

KaptchaConfig修改成从属性文件中读取

@Component
public class KaptchaConfig1 {
    private static Properties props = new Properties();
    @Bean
    public DefaultKaptcha defaultKaptcha() throws Exception {
        // 创建DefaultKaptcha对象
        DefaultKaptcha defaultKaptcha = new DefaultKaptcha();
        // 读取配置文件
        try {
            props.load(KaptchaConfig1.class.getClassLoader()
                       .getResourceAsStream("kaptcha.properties"));
        }catch (Exception e) {
            e.printStackTrace();
        }
        // 将Properties文件设到DefaultKaptcha对象中
        defaultKaptcha.setConfig(new Config(props));
        return defaultKaptcha;
    }
}

运行后，输入http://localhost:8080/kaptcha

了解hutool的验证码：https://www.hutool.cn/docs/#/captcha/%E6%A6%82%E8%BF%B0?id=circlecaptcha-%e5%9c%86%e5%9c%88%e5%b9%b2%e6%89%b0%e9%aa%8c%e8%af%81%e7%a0%81