How can i upload to MongoDB GridFS from loopback 4

Question

I'am new to Loopback 4. I was trying to upload files using loopback 4 to MongoDB GridFS. I used the file upload example from Loopback 4 examples but couldn't understand it enough to modify it?

protected configureFileUpload(destination?: string) {
    const url = 'mongodb://' + MongoDataSource.defaultConfig.user + ':' +
      MongoDataSource.defaultConfig.password
      + '@' + MongoDataSource.defaultConfig.host +
      ':' + MongoDataSource.defaultConfig.port +
      '/' + MongoDataSource.defaultConfig.database;
    const conn = mongoose.createConnection(url);
    let gfs;
    conn.once('open', () => {
      gfs = Grid(conn.db, mongoose.mongo);
      gfs.collection('uploads');
    });

    const storage = new GridFsStorage({
      url: url,
      file: (req: any, file: any) => {
        return new Promise((resolve, reject) => {
          //crypto create a unique id for the file to be uploaded
          crypto.randomBytes(16, (err, buf) => {
            if (err) return reject(err);
            const filename = buf.toString('hex') + path.extname(file.originalname);
            const fileInfo = {
              filename: filename,
              bucketName: 'bucketName',
              metadata: {
                originalName: file.originalname,
                encoding: file.encoding,
                mimetype: file.mimetype,
                size: file.size,
                expires: Date.now() + 1000 * 60 * 60
              }
            }
            resolve(fileInfo)
          })
        });
      }
    });
    storage;

    return multer({storage: storage}).any();
  }

Answer 1

This how I solved my own problem

import {inject} from '@loopback/core';
import {
  repository
} from '@loopback/repository';
import {
  getModelSchemaRef,
  post,
  Request,
  requestBody,
  Response,
  response,
  RestBindings
} from '@loopback/rest';
import crypto from 'crypto';
import multer from 'multer';
import {GridFsStorage} from 'multer-gridfs-storage';
import path from 'path';
import {MongoDataSource} from '../datasources';
import {FILE_UPLOAD_SERVICE} from '../keys';
import {Gridfs} from '../models';
import {GridfsRepository} from '../repositories';
import {FileUploadHandler} from '../types';

const url = 'mongodb://' + MongoDataSource.defaultConfig.user +
  ':' + MongoDataSource.defaultConfig.password +
  '@' + MongoDataSource.defaultConfig.host +
  ':' + MongoDataSource.defaultConfig.port +
  '/' + MongoDataSource.defaultConfig.database;

var storage = new GridFsStorage({
  url: url,
  file: (req: any, file: any) => {
    return new Promise((resolve, reject) => {
      //crypto create a unique id for the file to be uploaded
      crypto.randomBytes(16, (err, buf) => {
        if (err) return reject(err);
        const filename = buf.toString('hex') + path.extname(file.originalname);
        const fileInfo = {
          filename: filename,
          bucketName: 'documents',
          metadata: {
            originalName: file.originalname,
            encoding: file.encoding,
            mimetype: file.mimetype,
            size: file.size,
            expires: Date.now() + 1000 * 60 * 60
          }
        }
        return resolve(fileInfo)
      })
    });
  }
});
const upload = multer({storage});

export class GridfsController {
  constructor(
    @repository(GridfsRepository)
    public gridfsRepository: GridfsRepository,
    @inject(FILE_UPLOAD_SERVICE) private handler: FileUploadHandler,
  ) {
    console.log(FILE_UPLOAD_SERVICE);
    console.log(handler);
  }

  @post('/gridfs')
  @response(200, {
    description: 'Tender model instance',
    content: {'multipart/form-data': {schema: getModelSchemaRef(Gridfs)}},
  })
  async create(
    @requestBody({
      content: {
        'multipart/form-data': {
          schema: getModelSchemaRef(Gridfs, {
            title: 'NewGridfs',
            exclude: ['id'],
          }),
        },
      },
    })
    gridfs: Omit<Gridfs, 'id'>,
  ): Promise<Gridfs> {
    return this.gridfsRepository.create(gridfs);
  }

  @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) => {
      upload.single('file')(request, response, err => {
        if (err) return reject(err);
        let file = request.file as any;
        resolve({
          id: file.id.toString(),
          originalName: file.originalname,
          encoding: file.encoding,
          mimetype: file.mimetype,
          size: file.size,
          expires: Date.now() + 1000 * 60 * 60
        });
      });
    });
  }
}

Apparently it's so much easy