Vue implements the operation code of clicking a button to download a file (backend Java)

/**
 * Download attachment * @param attachmentId
 * @return
 */
public ResponseEntity<byte[]> download(Long attachmentId) {
    // Check if the attachment exists SysAttachment sysAttachment = sysAttachmentMapper.selectSysAttachmentById(attachmentId);
    if (StringUtils.isNull(sysAttachment)) {
        return null;
    }

    ByteArrayOutputStream bos = null;
    InputStream ins = null;
    try {
        String fileName = sysAttachment.getOrgFileName();
        String ossFileName = sysAttachment.getUrl();
        bos = new ByteArrayOutputStream();
        ins = OssUtils.getInstance().getObject(ossFileName).getObjectContent();
        // Get data from the stream int len ​​= 0;
        byte[] buf = new byte[256];
        while ((len = ins.read(buf, 0, 256)) > -1) {
            bos.write(buf, 0, len);
        }

        // Prevent Chinese garbled characters fileName = URLEncoder.encode(fileName, "utf-8");
        // Set response headers HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Disposition", "attachment;filename=" + fileName);
        headers.add("Content-Type", sysAttachment.getContentType());
        // Set the response HttpStatus statusCode = HttpStatus.OK;
        ResponseEntity<byte[]> response = new ResponseEntity<byte[]>(bos.toByteArray(), headers, statusCode);
        return response;
    } catch (Exception e) {
        throw new CustomException("Download failed");
    finally
        try {
            if (ins != null) {
                ins.close();
            }
            if (bos != null) {
                bos.close();
            }
        } catch (Exception e) {
            throw new CustomException("Download failed");
        }
    }
}

const mimeMap = {
  xlsx: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
  xls: 'application/vnd.ms-excel',
  zip: 'application/zip',
  jpg: 'image/jpg',
  jpeg: 'image/jpeg',
  png: 'image/png',
  doc: 'application/msword',
  docx: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
  ppt: 'application/vnd.ms-powerpoint',
  txt: 'text/plain',
  pdf: 'application/pdf'
}

/**
 * Download attachment* @param path interface address* @param param request parameter*/
export function downloadAttachment(path, param) {
  var url = baseUrl + path + param
  axios({
    method: 'get',
    url: url,
    responseType: 'blob',
    headers: { 'Authorization': getToken() }
  }).then(res => {
    resolveBlob(res, res.data.type)
  })
}

/**
 * Parse blob response content and download * @param {*} res blob response content * @param {String} mimeType MIME type */
export function resolveBlob(res, mimeType) {
  const aLink = document.createElement('a')
  var blob = new Blob([res.data], { type: mimeType })
  // Get filename from the response headers, and the file name set by backend response.setHeader("Content-disposition", "attachment; filename=xxxx.docx");
  var patt = new RegExp('filename=([^;]+\\.[^\\.;]+);*')
  var contentDisposition = decodeURI(res.headers['content-disposition'])
  var result = patt.exec(contentDisposition)
  var fileName = result[1]
  fileName = fileName.replace(/\"/g, '')
  aLink.href = URL.createObjectURL(blob)
  aLink.setAttribute('download', fileName) // Set the download file name document.body.appendChild(aLink)
  aLink.click()
  document.body.removeChild(aLink);
}

import { downloadAttachment } from "@/utils/download"
Vue.prototype.downloadAttac = downloadAttachment

<el-button
    type="text"
    icon="el-icon-download"
    size="mini"
    @click="downloadAttachRow(scope.row.attachmentId)"
    ></el-button>

/** Download attachment */
downloadAttachRow(attachId) {
    this.$confirm('Are you sure you want to download the file?', "Warning", {
        confirmButtonText: "Confirm",
        cancelButtonText: "Cancel",
        type: "warning"
    }).then(() => {
        this.downloadAttac('/system/attachment/download/', attachId)
    }).then(() => {
        this.msgSuccess("Download successful")
    }).catch(() => {})
}