Summary of front-end implementation of downloading files (including compressed package downloads)

The default and simplest download method is: window.open (backend interface API path) , but this method has disadvantages: because it is a new window opening method, the front-end display will flash every time.

In addition, if you use the window.open (file URL) method:

• PDF, office documents, psd: direct download.
• Pictures and txt: When previewing in a new window, it will not be downloaded; and when txt is previewed, Chinese garbled characters sometimes appear.

1. Download according to file URL

Implementation principle: Download through a tag.

/**
 * @method 下载单个文件（文件类型可任意：.png、txt、office文档、.psd等）
 * @param { String } url - 文件的http完整路径, 如：http: //xxx.png
 * @param { String } fileName - 文件名，注意是要带文件后缀名，如：xxx.png
 * @doc https://blog.csdn.net/weixin_39547158/article/details/110851570
 */
export function downloadFile(url: string, fileName: string) {
  return new Promise((resolve, reject) => {
    const xhr = new XMLHttpRequest();
    xhr.open('GET', url, true);
    xhr.responseType = 'blob';
    xhr.upload.onprogress = (e) => {
      if (e.lengthComputable) {
        let progress = e.loaded / e.total;
        console.log('文件上传进度是', progress);
      }
    };
    xhr.onload = function () {
      const url = window.URL.createObjectURL(xhr.response);
      const eleLink = document.createElement('a');
      eleLink.href = url;
      eleLink.download = `${fileName}`;
      eleLink.style.display = 'none';
      document.body.appendChild(eleLink);
      eleLink.click();
      document.body.removeChild(eleLink);
      resolve('success');
    };
    xhr.onerror = (e) => {
      console.log('请求错误回调', e);
      message.warning('下载文件失败')
      reject(e);
    };
    xhr.send();
  });
}

2. Excel file: call the background interface to return the file stream, and the front-end downloads the file

Implementation principle: Call the backend interface and return blob, and the front end uses the file-saver library to implement downloading.

// 下载excel文件
import { saveAs } from 'file-saver';

const downloadTemplate = async () => {
  try {
    const params = { ... } // 传参
    const res = await generateDownStreamReconciliationUsingGET(params);
    // res为返回结果
    if (res) {
      const blob = new Blob([res], { type: 'application/vnd.ms-excel' });
      FileSaver.saveAs(blob, '对账单.xlsx');
      console.log('对账单下载成功')
    }
  } catch (e) {
    console.log(e);
  } finally {
    console.log('finally')
  }
};

// 生成对账excel模板表格API
export async function generateDownStreamReconciliationUsingGET(
  params: API.generateDownStreamReconciliationUsingGETParams,
  options?: { [key: string]: any },
) {
  return request<any>(
    `${process.env.APP_HOST_WAYBILL}/xxx/generateDownStreamReconciliation`,
    {
      method: 'GET',
      responseType: 'blob',  // 必须写该行，否则：后台返回的是string，不是blob且文件下载后，会出现打不开问题。
      params: {
        ...params,
      },
      ...(options || {}),
    },
  );
}

3. Multi-file URL download, front-end generated compressed package download

Implementation principle: jszip library + file-saver library

import { getBlobOfUrl } from '@/services/common';
import { saveAs } from 'file-saver';
import JSZip from 'jszip';
import { message } from 'antd';

/**
 * @method 同时下载多文件,并生成一个压缩包
 * @param { Object[] } fileInfoList - 文件列表
 * @param { String } urlField - 文件URL的字段名
 * @param { String } fileNameField - 文件名的字段名
 * @param { String } folderName - 压缩包 & 文件夹名称
 */
export function downloadAsZip(
  fileInfoList: any[],
  folderName = '文件压缩包',
  urlField = 'filePath',
  fileNameField = 'name',
) {
  return new Promise((resolve, reject) => {
    const zip = new JSZip();
    // const folder = zip.folder(folderName); // 创建文件夹
    const promisesList = fileInfoList.map((item) => {
      return getBlobOfUrl(item[urlField])
        .then((data) => {
          // console.log(data); // Blob
          // folder.file(item[fileNameField], data, { binary: true }); // 往文件夹中存放文件
          zip.file(item[fileNameField], data, { binary: true }); // 不创建文件夹
        })
        .catch((e) => {
          console.log(e);
          message.warning(e?.message || '获取文件流失败')
        });
    });
    Promise.all(promisesList)
      .then(() => {
        zip
          .generateAsync({ type: 'blob' })
          .then((content) => {
            saveAs(content, folderName);
            resolve('success');
          })
          .catch((e) => {
            message.warning(e?.message || '生成压缩包失败')
            reject(e);
          });
      })
      .catch((e) => {
        message.warning(e?.message || '批量获取文件流失败')
        reject(e);
      });
  });
}

import { request } from 'umi';

/**
 * @method 根据文件URL获取blob数据流的API
 * @param { String } fileUrl - 文件完整路径，如：http://xxx.png
 */
export function getBlobOfUrl(fileUrl: string) {
  return request(fileUrl, {
    method: 'GET',
    responseType: 'blob', // 设置后台返回的内容类型为blob
    params: {
      notAuthorization: true,
    },
  });
}