NestJS - Backend Recipes

Installation

Install the Filejar client and required dependencies:

npm install filejar @nestjs/platform-express

Setup

Create Filejar Client

Create a Filejar service in your NestJS application:

import { Injectable } from '@nestjs/common';
import Filejar from 'filejar';

@Injectable()
export class FilejarService {
  private filejar: Filejar;

  constructor() {
    this.filejar = new Filejar({
      apiKey: process.env.FILEJAR_API_KEY,
    });
  }

  getClient() {
    return this.filejar;
  }
}

Register File Interceptor

File upload limits are configured directly in the interceptor options (shown in the controller examples below).

Single File Upload Endpoint

Create a controller to upload a single file:

import { Controller, Post, UseInterceptors, UploadedFile, Get, Param, BadRequestException, InternalServerErrorException } from '@nestjs/common';
import { FileInterceptor } from '@nestjs/platform-express';
import { FilejarService } from './filejar.service';
import { fileRepo } from '@/lib/db-repo';

@Controller('api/files')
export class FilesController {
  constructor(private readonly filejarService: FilejarService) {}

  @Post('upload')
  @UseInterceptors(FileInterceptor('file', {
    limits: { fileSize: 10 * 1024 * 1024 }, // 10MB limit
  }))
  async uploadFile(@UploadedFile() file: Express.Multer.File) {
    if (!file) {
      throw new BadRequestException('No file uploaded');
    }

    // Convert buffer to File-like object for uploadFile
    const fileObj = new File([file.buffer], file.originalname, {
      type: file.mimetype,
    });

    // Upload file to Filejar
    // The body parameter is optional - Filejar will automatically use the file's original name
    const result = await this.filejarService.getClient().upload.uploadFile([fileObj]);
    // Or with explicit file name:
    // const result = await this.filejarService.getClient().upload.uploadFile([fileObj], {
    //   body: [{ file_name: file.originalname }],
    // });

    if (!result.response || result.response.length === 0) {
      throw new InternalServerErrorException('Failed to upload file');
    }

    const uploadResult = result.response[0];
    const acknowledged = result.acknowledge[0];
    
    // Check if acknowledgment was successful
    if ('error' in acknowledged) {
      throw new InternalServerErrorException(acknowledged.error);
    }

    // Construct file URL using the key
    const fileUrl = `https://cdn.filejar.dev/${uploadResult.key}`;
    
    // Store file metadata in database
    const savedFile = await fileRepo.create({
      key: uploadResult.key,
      uploadId: uploadResult.upload_id,
      originalName: file.originalname,
      contentType: acknowledged.content_type,
      size: acknowledged.size,
      url: fileUrl,
      uploadedBy: 'user-id', // Get from your auth guard
    });

    return {
      success: true,
      file: savedFile,
    };
  }
}

Multiple Files Upload Endpoint

Create an endpoint to upload multiple files:

import { FilesInterceptor } from '@nestjs/platform-express';
import { UploadedFiles } from '@nestjs/common';

@Controller('api/files')
export class FilesController {
  // ... constructor and other methods

  @Post('upload-multiple')
  @UseInterceptors(FilesInterceptor('files', 10, {
    limits: { fileSize: 10 * 1024 * 1024 }, // 10MB limit
  }))
  async uploadFiles(@UploadedFiles() files: Express.Multer.File[]) {
    if (!files || files.length === 0) {
      throw new BadRequestException('No files uploaded');
    }

    // Convert buffers to File-like objects
    const fileObjs = files.map(file => 
      new File([file.buffer], file.originalname, { type: file.mimetype })
    );

    // Upload all files to Filejar
    // The body parameter is optional - Filejar will automatically use each file's original name
    const result = await this.filejarService.getClient().upload.uploadFile(fileObjs);
    // Or with explicit file names:
    // const result = await this.filejarService.getClient().upload.uploadFile(fileObjs, {
    //   body: files.map(file => ({ file_name: file.originalname })),
    // });

    if (!result.response || result.response.length === 0) {
      throw new InternalServerErrorException('Failed to upload files');
    }

    // Store file metadata in database
    const filePromises = result.response.map(async (uploadResult, index) => {
      const originalFile = files[index];
      const acknowledged = result.acknowledge[index];
      
      // Skip if acknowledgment failed
      if ('error' in acknowledged) {
        console.error(`Failed to acknowledge ${originalFile.originalname}:`, acknowledged.error);
        return null;
      }

      // Construct file URL using the key
      const fileUrl = `https://cdn.filejar.dev/${uploadResult.key}`;
      
      const savedFile = await fileRepo.create({
        key: uploadResult.key,
        uploadId: uploadResult.upload_id,
        originalName: originalFile.originalname,
        contentType: acknowledged.content_type,
        size: acknowledged.size,
        url: fileUrl,
        uploadedBy: 'user-id',
      });

      return savedFile;
    });

    const uploadedFiles = (await Promise.all(filePromises)).filter(file => file !== null);

    return {
      success: true,
      files: uploadedFiles,
      count: uploadedFiles.length,
    };
  }
}

Retrieve Files from Database

Create endpoints to retrieve file information:

import { fileRepo } from '@/lib/db-repo';
import { NotFoundException } from '@nestjs/common';

@Controller('api/files')
export class FilesController {
  // ... constructor and other methods

  @Get(':id')
  async getFile(@Param('id') id: string) {
    const file = await fileRepo.findById(id);

    if (!file) {
      throw new NotFoundException('File not found');
    }

    return file;
  }

  @Get()
  async getAllFiles() {
    const files = await fileRepo.findAll();

    return { files };
  }
}

Client-Side Usage

Upload Single File

// Client-side: Upload single file
async function uploadFile(file: File) {
  const formData = new FormData();
  formData.append('file', file);

  const response = await fetch(`${API_BASE_URL}/api/files/upload`, {
    method: 'POST',
    body: formData,
  });

  const data = await response.json();
  return data.file; // Contains id, filejarId, filejarKey, name, url
}

Upload Multiple Files

// Client-side: Upload multiple files
async function uploadFiles(files: File[]) {
  const formData = new FormData();
  files.forEach(file => {
    formData.append('files', file);
  });

  const response = await fetch(`${API_BASE_URL}/api/files/upload-multiple`, {
    method: 'POST',
    body: formData,
  });

  const data = await response.json();
  return data.files; // Array of file objects
}

Retrieve File

Simply use the file key to construct the URL:

// Direct URL access using the file key
const fileUrl = `https://cdn.filejar.dev/${key}`;

// Example: Display file in img tag
<img src={`https://cdn.filejar.dev/${fileKey}`} alt="Uploaded file" />

Complete Example

Here’s a complete NestJS module setup:

import { Module } from '@nestjs/common';
import { FilesController } from './files.controller';
import { FilejarService } from './filejar.service';

@Module({
  controllers: [FilesController],
  providers: [FilejarService],
})
export class FilesModule {}

// files.controller.ts
import { Controller, Post, Get, Param, UseInterceptors, UploadedFile, UploadedFiles, BadRequestException, InternalServerErrorException, NotFoundException } from '@nestjs/common';
import { FileInterceptor, FilesInterceptor } from '@nestjs/platform-express';
import { FilejarService } from './filejar.service';
import { fileRepo } from '@/lib/db-repo';

@Controller('api/files')
export class FilesController {
  constructor(private readonly filejarService: FilejarService) {}

  @Post('upload')
  @UseInterceptors(FileInterceptor('file', {
    limits: { fileSize: 10 * 1024 * 1024 },
  }))
  async uploadFile(@UploadedFile() file: Express.Multer.File) {
    // ... single upload code from above
  }

  @Post('upload-multiple')
  @UseInterceptors(FilesInterceptor('files', 10, {
    limits: { fileSize: 10 * 1024 * 1024 },
  }))
  async uploadFiles(@UploadedFiles() files: Express.Multer.File[]) {
    // ... multiple upload code from above
  }

  @Get(':id')
  async getFile(@Param('id') id: string) {
    // ... get file code from above
  }

  @Get()
  async getAllFiles() {
    // ... get all files code from above
  }
}

​Installation

​Setup

​Create Filejar Client

​Register File Interceptor

​Single File Upload Endpoint

​Multiple Files Upload Endpoint

​Retrieve Files from Database

​Client-Side Usage

​Upload Single File

​Upload Multiple Files

​Retrieve File

​Complete Example