javascript Blob object to achieve file download

// Download export function download(query,newFileName) {
  return request({
    url: '/file/download',
    method: 'get',
    responseType: 'blob',
    params: query
  }).then((res) => {
    /**
     * Blob download ideas * 1) Use ajax to initiate a request and specify the receiving type as blob (responseType: 'blob')
     * 2) Read the content-disposition in the header information returned by the request. The returned file name is in it (or you can customize the file name and skip this step)
     * 3) Use URL.createObjectURL to convert the requested blob data into a downloadable URL address* 4) Use the a tag to download* 
     */
    let blob = res.data
    // Get filename from the response headers, and the file name set by backend response.setHeader("Content-disposition", "attachment; filename=xxxx.docx");
    // let patt = new RegExp('filename=([^;]+\\.[^\\.;]+);*')
    // let contentDisposition = decodeURI(res.headers['content-disposition'])
    // let result = patt.exec(contentDisposition)
    // let fileName = result[1]

    //Convert the requested blob data into a downloadable URL address let url = URL.createObjectURL(blob)
    // Create a download tag <a>
    const aLink = document.createElement('a')
    aLink.href = url
    // 2. Use the custom file name directly to set the download file name aLink.setAttribute('download', newFileName )
    document.body.appendChild(aLink)
    //Simulate click to download aLink.click()
    // Remove the download tag document.body.removeChild(aLink);
  })
}

//Download download(row) {
      // filePath: file path, for example: e:\upload\
	  // fileName: file name, for example: a.xlsx
      let form = {
        filePath: row.filePath,
        fileName: row.fileName,
      };
      //Download, row.fileOriginalName is the original name of the file, which is only used to name the file when downloading. download(form, row.fileOriginalName);
    }
// Since I am using Alibaba's OSS service, I only need to pass a file path back to the backend, query the OSS interface according to the file path to get the returned file stream, for example (BufferedInputStream), and set the return type in the response header

	// response: response // filePath: file path, for example: e:\upload\
	// fileName: file name, for example: a.xlsx
   public void download(HttpServletResponse response, String filePath, String fileName) {
        //File name to be downloaded response.reset();
        response.setHeader("Content-Disposition", "attachment;filename=" + fileName);
        response.setContentType("application/octet-stream");
        response.setCharacterEncoding("utf-8");
        // Create an OSSClient instance.
        OSS ossClient = new OSSClientBuilder().build(endpoint, accessKeyId, accessKeySecret);
        // ossObject contains the name of the storage space where the file is located, the file name, file meta information, and an input stream.
        OSSObject ossObject = ossClient.getObject(bucketName, filePath + "/" + fileName);

        BufferedInputStream in = null;
        BufferedOutputStream out = null;

        byte[] buff = new byte[1024];
        int length = 0;
        try {
            in = new BufferedInputStream(ossObject.getObjectContent());
            out = new BufferedOutputStream(response.getOutputStream());
            while ((length = in.read(buff)) != -1){
                out.write(buff,0,length);
            }
        } catch (IOException e) {
            e.printStackTrace();
        finally
            if(out != null){
                try {
                    out.flush();
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(in != null){
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (ossClient != null) {
                ossClient.shutdown();
            }
        }
    }