Java 二维码生成工具

现在二维码是一个非常常用，如微信二维码、支付宝二维码！那它如何实现呢？

public class QrCodeUtil {

    /**
     * 生成包含字符串信息的二维码图片
     *
     * @param outputStream 文件输出流路径
     * @param content      二维码携带信息
     * @param qrCodeSize   二维码图片大小
     * @param imageFormat  二维码的格式
     * @throws WriterException
     * @throws IOException
     */
    public static boolean createQrCode(OutputStream outputStream, String content, int qrCodeSize, String imageFormat) throws WriterException, IOException {
        //设置二维码纠错级别ＭＡＰ
        Hashtable<EncodeHintType, ErrorCorrectionLevel> hintMap = new Hashtable<EncodeHintType, ErrorCorrectionLevel>();
        hintMap.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);  // 矫错级别
        QRCodeWriter qrCodeWriter = new QRCodeWriter();
        //创建比特矩阵(位矩阵)的QR码编码的字符串
        BitMatrix byteMatrix = qrCodeWriter.encode(content, BarcodeFormat.QR_CODE, qrCodeSize, qrCodeSize, hintMap);
        // 使BufferedImage勾画QRCode  (matrixWidth 是行二维码像素点)
        int matrixWidth = byteMatrix.getWidth();
        BufferedImage image = new BufferedImage(matrixWidth - 200, matrixWidth - 200, BufferedImage.TYPE_INT_RGB);
        image.createGraphics();
        Graphics2D graphics = (Graphics2D) image.getGraphics();
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, matrixWidth, matrixWidth);
        // 使用比特矩阵画并保存图像
        graphics.setColor(Color.BLACK);
        for (int i = 0; i < matrixWidth; i++) {
            for (int j = 0; j < matrixWidth; j++) {
                if (byteMatrix.get(i, j)) {
                    graphics.fillRect(i - 100, j - 100, 1, 1);
                }
            }
        }
        return ImageIO.write(image, imageFormat, outputStream);
    }

    /**
     * 读二维码并输出携带的信息
     */
    public static void readQrCode(InputStream inputStream) throws IOException {
        //从输入流中获取字符串信息
        BufferedImage image = ImageIO.read(inputStream);
        //将图像转换为二进制位图源
        LuminanceSource source = new BufferedImageLuminanceSource(image);
        BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
        QRCodeReader reader = new QRCodeReader();
        Result result = null;
        try {
            result = reader.decode(bitmap);
        } catch (ReaderException e) {
            e.printStackTrace();
        }
        System.out.println(result.getText());
    }

    /**
     * 生成并下载二维码
     * @param url 二维码对于URL
     * @param width 二维码宽
     * @param height 二维码高
     * @param format  二维码格式
     * @return
     * @throws WriterException
     * @throws IOException
     */
    public static ResponseEntity<byte[]> getResponseEntity(String url, int width, int height, String format) throws WriterException, IOException {
        Map<EncodeHintType, Object> hints = new HashMap<EncodeHintType, Object>();
        hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");
        BitMatrix bitMatrix = new MultiFormatWriter().encode(url,
                BarcodeFormat.QR_CODE, width, height, hints);// 生成矩阵
        //将矩阵转为Image
        BufferedImage image = MatrixToImageWriter.toBufferedImage(bitMatrix);
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        ImageIO.write(image, format, out);//将BufferedImage转成out输出流
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        return new ResponseEntity<byte[]>(out.toByteArray(),
                headers, HttpStatus.CREATED);
    }


    /**
     * 测试代码
     *
     * @throws WriterException
     */
    public static void main(String[] args) throws IOException, WriterException {
        String qcodeUrl = "otpauth://totp/%s?secret=%s";
        System.out.println(getResponseEntity(String.format(qcodeUrl,"admin","A4VH7IPPMNCHVF3F"),150,150,"png"));;
//        createQrCode(new FileOutputStream(new File("d:\\qrcode.jpg")), String.format(qcodeUrl,"admin","A4VH7IPPMNCHVF3F"), 900, "JPEG");
//        readQrCode(new FileInputStream(new File("d:\\qrcode.jpg")));
    }
}