Upload and Download — LoopBack

Download an example

$ lb4 example todo
$ cd loopback4-example-todo
$ npm i --save @loopback/authentication @loopback/authentication-jwt

Step 1:Create a controller class such as FileUploadController

import {inject} from '@loopback/core';
import {
  post,
  Request,
  requestBody,
  Response,
  RestBindings,
} from '@loopback/rest';
//import {FILE_UPLOAD_SERVICE} from '../keys';
//import {FileUploadHandler} from '../types';
/**
 * A controller to handle file uploads using multipart/form-data media type
 */
export class FileUploadController {
  
  @post('/files', {
    responses: {
      200: {
        content: {
          'application/json': {
            schema: {
              type: 'object',
            },
          },
        },
        description: 'Files and fields',
      },
    },
  })
  async fileUpload(
    @requestBody.file()
    request: Request,
    @inject(RestBindings.Http.RESPONSE) response: Response,
  ): Promise<object> {
    return new Promise<object>((resolve, reject) => {
      this.handler(request, response, err => {
        if (err) reject(err);
        else {
         resolve(FileUploadController.getFilesAndFields(request));
        }
      });
    });
  }
}

Step 2:Create a controller class such as FileDownloadController

import {inject} from '@loopback/core';
import {
  get,
  HttpErrors,
  oas,
  param,
  Response,
  RestBindings,
} from '@loopback/rest';
import fs from 'fs';
import path from 'path';
import {promisify} from 'util';
const readdir = promisify(fs.readdir);
const SANDBOX = path.resolve(__dirname, '../../.sandbox');
/**
 * A controller to handle file downloads using multipart/form-data media type
 */
export class FileDownloadController {
 @get('/files/{filename}')
  @oas.response.file()
  downloadFile(
    @param.path.string('filename') fileName: string,
    @inject(RestBindings.Http.RESPONSE) response: Response,
  ) {
    const file = validateFileName(fileName);
    response.download(file, fileName);
    return response;
  }
}
/**
 * Validate file names to prevent them goes beyond the designated directory
 * @param fileName - File name
 */
function validateFileName(fileName: string) {
  const resolved = path.resolve(SANDBOX, fileName);
  if (resolved.startsWith(SANDBOX)) return resolved;
  // The resolved file is outside sandbox
  throw new HttpErrors.BadRequest(`Invalid file name: ${fileName}`);
}