配置pom.xml

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

默认工具配置：KaptchaConfig

@Component
public class KaptchaConfig {
    @Bean
    public DefaultKaptcha getDefaultKaptcha() {
        DefaultKaptcha defaultKaptcha = new DefaultKaptcha();
        Properties properties = new Properties();
        // 图片边框
        properties.setProperty("kaptcha.border", "yes");
        // 边框颜色
        properties.setProperty("kaptcha.border.color", "105,179,90");
        // 字体颜色
        properties.setProperty("kaptcha.textproducer.font.color", "red");
        // 图片宽
        properties.setProperty("kaptcha.image.width", "100");
        // 图片高
        properties.setProperty("kaptcha.image.height", "34");
        // 字体大小
        properties.setProperty("kaptcha.textproducer.font.size", "30");
        // session key
        properties.setProperty("kaptcha.session.key", "code");
        // 验证码长度
        properties.setProperty("kaptcha.textproducer.char.length", "4");
        // 字体
        properties.setProperty("kaptcha.textproducer.font.names", "Consolas");
        // 设置字符串范围
        properties.setProperty("kaptcha.textproducer.char.string", "0123456789");
        Config config = new Config(properties);
        defaultKaptcha.setConfig(config);

        return defaultKaptcha;
    }
}

登录页面种植Cookie

// 获取种植的cookie
String cookieValue = IpUtils.getCookieValue(request, imgCookieName);
LOGGER.info("login cookieValue : {}", cookieValue);
if(cookieValue == null) {
    // 给前端种植一个cookie，用于图片验证码校验
    response.addCookie(new Cookie(imgCookieName, UUID.randomUUID().toString()));
}

生成图片API

/**
 * 验证码工具
 */
@Autowired
DefaultKaptcha defaultKaptcha;

/**
 * redis缓存数据
 */
@Autowired
private RedisTemplate<String, String> redisTemplate;

/**
 * 获取图片验证码
 * @throws IOException 
 */
@GetMapping("/verify")
public void verify(HttpServletRequest request, HttpServletResponse response) throws IOException {
    // 获取种植的cookie
    String cookieValue = IpUtils.getCookieValue(request, imgCookieName);
    LOGGER.info("verify cookieValue : {}", cookieValue);
    
    // 生产验证码字符串并保存到session中
    String createText = defaultKaptcha.createText();
    LOGGER.info("verify createText : {}", createText);
    
    // 缓存图片验证码到redis，设置超时时间1分钟
    redisTemplate.opsForValue().set(cookieValue, createText, 60, TimeUnit.SECONDS);
    
    // 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
    ByteArrayOutputStream jpegOutputStream = new ByteArrayOutputStream();
    BufferedImage challenge = defaultKaptcha.createImage(createText);
    ImageIO.write(challenge, "jpg", jpegOutputStream);
    
    // 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
    byte[] captchaChallengeAsJpeg = jpegOutputStream.toByteArray();
    response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
    response.setHeader("Pragma", "no-cache");
    response.setDateHeader("Expires", 0);
    response.setContentType("image/jpeg");
    ServletOutputStream responseOutputStream = response.getOutputStream();
    responseOutputStream.write(captchaChallengeAsJpeg);
    responseOutputStream.flush();
    responseOutputStream.close();
    LOGGER.info("verify end ... ");
}