1.demo-admin模块导入依赖

        <!--kaptcha依赖-->
        <dependency>
            <groupId>com.github.axet</groupId>
            <artifactId>kaptcha</artifactId>
            <version>0.0.9</version>
        </dependency>

2.创建kaptcha配置类

package com.lvxk.demo.admin.config;

import com.google.code.kaptcha.impl.DefaultKaptcha;
import com.google.code.kaptcha.util.Config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Properties;

/**
 * KaptchaConfig
 * Description: <br/>
 * date: 2020/5/5 15:17<br/>
 *
 * @author lvxk<br />
 * @since JDK 1.8
 */
@Configuration
public class KaptchaConfig {

    @Bean
    public DefaultKaptcha producer() {
        Properties properties = new Properties();
        properties.put("kaptcha.border", "no");
        properties.put("kaptcha.textproducer.font.color", "black");
        properties.put("kaptcha.textproducer.char.space", "5");
        Config config = new Config(properties);
        DefaultKaptcha defaultKaptcha = new DefaultKaptcha();
        defaultKaptcha.setConfig(config);
        return defaultKaptcha;
    }
}

3.创建controller，编写获取验证码接口

package com.lvxk.demo.admin.controller;

import com.google.code.kaptcha.Constants;
import com.google.code.kaptcha.Producer;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.apache.tomcat.util.http.fileupload.IOUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.image.BufferedImage;
import java.io.IOException;

/**
 * SysLoginController 获取验证码
 * Description: <br/>
 * date: 2020/5/5 15:19<br/>
 *
 * @author lvxk<br />
 * @since JDK 1.8
 */
@RestController
@RequestMapping("kaptcha")
@Api(tags = "验证码相关")
public class SysLoginController {

    @Autowired
    private Producer producer;

    @GetMapping("code")
    @ApiOperation(value = "获取验证码(5位)")
    public void captha(HttpServletResponse response, HttpServletRequest request) throws IOException {
        response.setHeader("Cache-Control","no-store,no-cache");
        response.setContentType("image/jpeg");
        //生成文字验证码
        String text = producer.createText();
        //生成图片验证码
        BufferedImage image = producer.createImage(text);
        //保存验证码到session中
        request.getSession().setAttribute(Constants.KAPTCHA_SESSION_KEY,text);
        ServletOutputStream out = response.getOutputStream();
        ImageIO.write(image,"jpg",out);
        IOUtils.closeQuietly(out);
    }
}

4.验证测试

image.png