生成验证码

    
    @GetMapping(value = "/randomImage")
    public SysResult randomImage(HttpServletResponse response){
        SysResult sysResult = new SysResult();
        try {
            //生成验证码
            final String BASE_CHECK_CODES = "qwertyuiplkjhgfdsazxcvbnmQWERTYUPLKJHGFDSAZXCVBNM1234567890";
            String code = RandomUtil.randomString(BASE_CHECK_CODES,4);

            //存到redis中
//            String lowerCaseCode = code.toLowerCase();
//
//            String realKey = Md5Util.md5Encode(lowerCaseCode+key, "utf-8");
//            log.info("获取验证码，Redis checkCode = {}，key = {}", code, key);
//            redisUtil.set(realKey, lowerCaseCode, 60);

            //返回前端
            String base64 = RandImageUtil.generate(code);
            log.info("验证码为："+code);
            sysResult.setData(base64);
        } catch (Exception e) {

            sysResult.setMsg("获取验证码出错"+e.getMessage());
            e.printStackTrace();
        }
        return sysResult;
    }

直接生成图片返回给前端

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Base64;
import java.util.Random;


public class RandImageUtil {

    public static final String key = "JEECG_LOGIN_KEY";

    
    private static final int width = 105;
    
    private static final int height = 35;

    
    private static final int count = 200;

    
    private static final int lineWidth = 2;

    
    private static final String IMG_FORMAT = "JPEG";

    
    private static final String BASE64_PRE = "data:image/jpg;base64,";

    
    public static void generate(HttpServletResponse response, String resultCode) throws IOException {
        BufferedImage image = getImageBuffer(resultCode);
        // 输出图象到页面
        ImageIO.write(image, IMG_FORMAT, response.getOutputStream());
    }

    
    public static String generate(String resultCode) throws IOException {
        BufferedImage image = getImageBuffer(resultCode);

        ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        //写入流中
        ImageIO.write(image, IMG_FORMAT, byteStream);
        //转换成字节
        byte[] bytes = byteStream.toByteArray();
        //转换成base64串
        String base64 = Base64.getEncoder().encodeToString(bytes).trim();
        //删除 rn
        base64 = base64.replaceAll("n", "").replaceAll("r", "");

        //写到指定位置
        //ImageIO.write(bufferedImage, "png", new File(""));

        return BASE64_PRE+base64;
    }

    private static BufferedImage getImageBuffer(String resultCode){
        // 在内存中创建图象
        final BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // 获取图形上下文
        final Graphics2D graphics = (Graphics2D) image.getGraphics();
        // 设定背景颜色
        // ---1
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, width, height);
        // 设定边框颜色
//		graphics.setColor(getRandColor(100, 200)); // ---2
        graphics.drawRect(0, 0, width - 1, height - 1);

        final Random random = new Random();
        // 随机产生干扰线，使图象中的认证码不易被其它程序探测到
        for (int i = 0; i < count; i++) {
            // ---3
            graphics.setColor(getRandColor(150, 200));

            // 保证画在边框之内
            final int x = random.nextInt(width - lineWidth - 1) + 1;
            final int y = random.nextInt(height - lineWidth - 1) + 1;
            final int xl = random.nextInt(lineWidth);
            final int yl = random.nextInt(lineWidth);
            graphics.drawLine(x, y, x + xl, y + yl);
        }
        // 取随机产生的认证码
        for (int i = 0; i < resultCode.length(); i++) {
            // 将认证码显示到图象中,调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
            // graphics.setColor(new Color(20 + random.nextInt(130), 20 + random
            // .nextInt(130), 20 + random.nextInt(130)));
            // 设置字体颜色
            graphics.setColor(Color.BLACK);
            // 设置字体样式
//			graphics.setFont(new Font("Arial Black", Font.ITALIC, 18));
            graphics.setFont(new Font("Times New Roman", Font.BOLD, 24));
            // 设置字符，字符间距，上边距
            graphics.drawString(String.valueOf(resultCode.charAt(i)), (23 * i) + 8, 26);
        }
        // 图象生效
        graphics.dispose();
        return image;
    }

    private static Color getRandColor(int fc, int bc) { // 取得给定范围随机颜色
        final Random random = new Random();
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }

        final int r = fc + random.nextInt(bc - fc);
        final int g = fc + random.nextInt(bc - fc);
        final int b = fc + random.nextInt(bc - fc);

        return new Color(r, g, b);
    }
}

前端代码：

将得到的数据结果放入即可

结果：

        //获得用户发过来的验证码 进行校验
        String captcha = sysLoginModel.getCaptcha();//获得验证码
        if(captcha==null){
            result.error500("验证码无效");
            return result;
        }
        //去除大小写
        String lowerCaseCaptcha = captcha.toLowerCase();
        //与redis中的进行比对。----------------
		String realKey = Md5Util.md5Encode(lowerCaseCaptcha+sysLoginModel.getCheckKey(), "utf-8");
		Object checkCode = redisUtil.get(realKey);
		//当进入登录页时，有一定几率出现验证码错误 #1714
		if(checkCode==null || !checkCode.toString().equals(lowerCaseCaptcha)) {
            log.warn("验证码错误，key= {} , Ui checkCode= {}, Redis checkCode = {}", sysLoginModel.getCheckKey(), lowerCaseCaptcha, checkCode);
			result.error500("验证码错误");
			return result;
		}