二维码生成/下载

一：引入pom

<!-- zxing二维码生成 -->
<dependency>
    <groupId>com.google.zxing</groupId>
    <artifactId>core</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
    <groupId>com.google.zxing</groupId>
    <artifactId>javase</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
</dependency>
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
</dependency>

二：生成/下载二维码

/**
 * 二维码请求
 *
 * @param resp
 * @param qrUrl
 * @throws IOException
 */
@RequestMapping(value = "/getQRcode", method = {RequestMethod.POST, RequestMethod.GET})
@ApiOperation(value = "获取二维码", response = ApiResponse.class)
@SignIgnore
@VisitorAccessible
public ApiResponse getQRcode(HttpServletResponse resp, String qrUrl) throws IOException {
    if (qrUrl != null && !"".equals(qrUrl)) {
        resp.setHeader("Content-type", "image/jpeg");
        resp.setHeader("Content-disposition","attachment;filename=code.jpeg");  // TODO: 2018/4/3 加上此行浏览器会自动下载,否则浏览器只展示图片 
        OutputStream stream = null;
        try {
            int width = 400;//图片的宽度
            int height = 400;//高度
            stream = resp.getOutputStream();

            QRCodeWriter writer = new QRCodeWriter();
            BitMatrix m = writer.encode(qrUrl, BarcodeFormat.QR_CODE, height, width);
            MatrixToImageWriter.writeToStream(m, "jpeg", stream);
        } catch (WriterException e) {
            e.printStackTrace();
        } finally {
            if (stream != null) {
                stream.flush();
                stream.close();
            }
        }
    }
    return new ApiResponse();
}