1：工具类

@Slf4j
public class RandomValidateCode {


    private static String baseNumLetter = "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ";
    private static String font = "微软雅黑";

    //绘制验证码图片,返回验证码文本内容
    public static String drawRandomText(int width, int height, BufferedImage verifyImg) {

        Graphics2D graphics = (Graphics2D) verifyImg.getGraphics();
        graphics.setColor(Color.WHITE);//设置画笔颜色-验证码背景色
        graphics.fillRect(0, 0, width, height);//填充背景
        graphics.setFont(new Font(font, Font.BOLD, 30));

        StringBuffer sBuffer = new StringBuffer();
        int x = 10;  //旋转原点的 x 坐标
        String ch = "";
        Random random = new Random();
        for (int i = 0; i < 4; i++) {
            graphics.setColor(getRandomColor());
            //设置字体旋转角度
            int degree = random.nextInt() % 30;  //角度小于30度
            int dot = random.nextInt(baseNumLetter.length());
            ch = baseNumLetter.charAt(dot) +"";
            sBuffer.append(ch);
            //正向旋转
            graphics.rotate(degree * Math.PI / 180, x, 45);
            graphics.drawString(ch, x, 45);
            //反向旋转
            graphics.rotate(-degree * Math.PI / 180, x, 45);
            x += 48;
        }

        //画干扰线
        /*for (int i = 0; i < 30; i++) {
            // 设置随机颜色
            graphics.setColor(getRandomColor());
            // 随机画线
            graphics.drawLine(random.nextInt(width), random.nextInt(height),
                    random.nextInt(width), random.nextInt(height));

        }

        //添加噪点
        for (int i = 0; i < 200; i++) {
            int x1 = random.nextInt(width);
            int y1 = random.nextInt(height);
            graphics.setColor(getRandomColor());
            graphics.fillRect(x1, y1, 2, 2);

        }*/
        log.info("======图文验证:{}", sBuffer.toString());
        return sBuffer.toString();
    }

    //获取随机颜色

    private static Color getRandomColor() {
        Random ran = new Random();
        Color color = new Color(ran.nextInt(256),
                ran.nextInt(256), ran.nextInt(256));
        return color;
    }

2：方法层

String getCheckCode(String phone, BufferedImage verifyImg);

3：业务层

@Override
public String getCheckCode(String phone, BufferedImage verifyImg) {
    String randomText = RandomValidateCode.drawRandomText(BaseUtils.TWO_HUNDRED, BaseUtils.SIXTY, verifyImg);
    log.info("RandomValidateCode randomText:{} ", randomText);
    this.stringRedisTemplateOne.opsForValue().set(BaseUtils.KEY_IMAGE + phone, randomText, BaseUtils.CODE_TIME, BaseUtils.TIME_UNIT);
    return randomText;
}

4：控制层

@PostMapping("/getCheckCode")
public void getCheckCode(HttpServletResponse response, HttpServletRequest request, @RequestParam(value = "phone") String phone) {
    try {
        BufferedImage verifyImg = new BufferedImage(BaseUtils.TWO_HUNDRED, BaseUtils.SIXTY, BufferedImage.TYPE_INT_RGB);
        request.getSession().setAttribute("verifyCode", userService.getCheckCode(phone, verifyImg));
        response.setContentType("image/png");//必须设置响应内容类型为图片，否则前台不识别
        OutputStream os = response.getOutputStream(); //获取文件输出流
        ImageIO.write(verifyImg, "png", os);//输出图片流
        os.flush();
        os.close();//关闭流
    } catch (IOException e) {

    }
}

5：页面效果