NestJS API File Operations Using Azure Blob Storage

In this article, we are going to use Azure Blob Storage for all file operations like uploading, downloading, and deleting files from the NestJS API endpoint.

Azure Blob Storage:

Azure blob storage is Microsoft cloud storage. Blob storage can store a massive amount of file data as unstructured data. The unstructured data means not belong to any specific type, which means text or binary data. So something like images or pdf or videos to store in the cloud, then the most recommended is to use the blob store.

The key component to creating azure blob storage resource:

Storage Account:-

A Storage account gives a unique namespace in Azure for all the data we will save. Every object that we store in Azure Storage has an address. The address is nothing but the unique name of our Storage Account name. The combination of the account name and the Azure Storage blob endpoint forms the base address for each object in our Storage account. For example, if our Storage Account is named as 'myazurestorageaccount' then the base address will be like 'https://myazurestorageaccount.blob.core.windows.net'.

Containers:-

The containers are like folders in the file system. So storage account can have an unlimited number of containers. Inside each container can have an unlimited number of blobs.

Blobs:- 

Azure gives 3 types of blobs:

• Block Blobs - Block of data managed individually. Most recommended for file uploading.
• Append Blobs - Contains Block of data but with append operation.
• Page Blogs

Create Azure Blob Storage In Azure Portal:

To consume any azure service we have to signup for the Azure portal, an additional bonus of the azure portal is users can use most of the service with free subscriptions. The free subscription is very handy for developers to learn about the azure service.

On the Azure portal dashboard page click on 'Create a resource.

Search for 'Storage Account' and select to create.

Fill 'Create Storage Account' form.

• 'Resource group' - enter the name of the resource group. Resource groups are just separators or wrappers.
• 'Storage account name' - enter the unique name and this name will be used for creating the base address.
• 'Location - you can select the default or choose your nearest location value.
• 'Performance' - chose your preferred option(for free subscription go for the 'Standard' option)
• 'Account Kind' - 'StorageV2(general purpose v2)' is the recommended option.
• 'Replication' - chose your preferred option or select the default option.

Then remaining tabs you can skip or chose for creating the Storage Account.

Once storage created. In the left side menu under 'Blob Service' select 'Containers' then click on Create new container which opens a form for creation.

Inside of the 'New Container' form, enter your Container name and then select option 'access level' for the container.

Now while creating the container I'm assigning access level 'anonymous read access for container and blob' which gives permission to access the blobs with the domain address directly.

Create NestJS Application:

Now our goal is to create NestJs endpoints for operating files in Azure Blob Storage. So let's create a NestJS application.

Command To Install CLI:
npm i -g @nestjs/cli

Command To Create NestJS App:
nest new your_project_name

Install Azure Blob Storage NodJS Package:

npm install @azure/storage-blob

Install NodeJS Multer Package:

In NestJS for handling file upload operation, it is the best choice to install the 'Multer' package. It is very effective in reading 'multipart/formdata'. The'Multer' also provides more type safety.

Multer Package:
npm i -D @types/multer

Azure Connectionstring:

There different ways like Authentication, ConnectionString, SharedSASToken, etc to communicate with the Azure Blob Storage.

In this demo, I'm going to use the ConnectionString in NestJS API to interact with the Azure Blob Storage. In Azure Storage Account, the left-hand side under settings select 'Access Keys' menu and it will display 'Key1' and 'Key2' access keys. We can choose any one of them.

NestJS Endpoint For Uploading File To Azure Blob Storage:

We have to implement our logic to create a file upload endpoint in NestJS.

src/app.service.ts:

import { BlobServiceClient, BlockBlobClient } from '@azure/storage-blob';
import { Injectable } from '@nestjs/common';


@Injectable()
export class AppService {
  azureConnection = "DefaultEndpointsProtocol=https;AccountName=naveenazurestore;AccountKey=NLNxbk2ElnaMaUucTLt1zQDU1eOznjYUmCaiIeJB6O+934iedXSmss+r5gDePmZE6y99X8zZ8AItA==;EndpointSuffix=core.windows.net";
  containerName = "upload-file";
  

  getBlobClient(imageName:string):BlockBlobClient{
    const blobClientService = BlobServiceClient.fromConnectionString(this.azureConnection);
    const containerClient = blobClientService.getContainerClient(this.containerName);
    const blobClient = containerClient.getBlockBlobClient(imageName);
    return blobClient;
  }

  async upload(file:Express.Multer.File){
    const blobClient = this.getBlobClient(file.originalname);
    await blobClient.uploadData(file.buffer);
  }
}

• (Line: 1) Instances like 'BlobServiceClient' & 'BlockBlobClient' loading from '@azure/storage-blob'.
• (Line: 7) Azure connection string.
• (Line: 8) Azure Blob Storage container name. This our target container to upload our files from our NestJS API endpoint.
• (Line: 11-16) The 'getBlobClient' method returns 'BlockBlobClient' from our specified 'Blob'(here Blob means our file to upload).
• (Line: 12)  Configuring our azure connection string into the 'BlobServiceClient'.
• (Line: 13)  Configuring our container name.
• (Line: 14)  Configuring the name of our file to be upload and returning the 'BlockBlobClient' instance. The 'BlockBlobClient' now contains all the configurations like connection, container, filename.
• (Line: 18-21) The 'upload' method contains logic to upload files to Azure Blob Storage. Its input parameter is a file of type 'Multer.File'.
• (Line: 19) Fetching 'BlockBlobClient' instance.
• (Line: 20) Invoking file upload call by using 'uploadData' method from the 'BlockBlobClient' instance. The 'uploadData' takes file buffer as input.

src/app.controller.cs:

import { Controller, Post, UploadedFile, UseInterceptors } from '@nestjs/common';
import { FileInterceptor } from '@nestjs/platform-express';
import { AppService } from './app.service';

@Controller()
export class AppController {
  constructor(private readonly appService: AppService) {}


  @Post('upload')
  @UseInterceptors(FileInterceptor('myfile'))
  async upload(@UploadedFile() file: Express.Multer.File):Promise<string>{
    await this.appService.upload(file);
    return "uploaded";
  }
}

• (Line: 11) The 'FileInterceptor' reads all file stream from the 'myfile'(name attribute value or form data value).
• (Line: 12) The '@UploadedFile()' decorator grabs the all file information and assigns it to the variable like 'file' in our sample. Here we are defining the type as 'Express.Multer.File'.
• (Line: 13) Passing file to the 'upload' method.

Now let's test our endpoint from the 'Postman' tool(Note: While uploading from Postman tool, clear all headers).

Now check in the Azure dashboard.

Create NestJS Endpoint To Read File:

The new endpoint going to fetch the steam of file from the Azure Blob Storage and then render it on the browser.

src/app.service.ts:

async getfileStream(fileName: string){
  const blobClient = this.getBlobClient(fileName);
  var blobDownloaded = await blobClient.download();
  return blobDownloaded.readableStreamBody;
}

• Fetching required image or file stream from Azure Blob Storage by using the 'download()' method of 'BlockBlobClien' instance.

src/app.controller:

import { Controller, Get, Header, Post, Query, Res, UploadedFile, UseInterceptors } from '@nestjs/common';
import { FileInterceptor } from '@nestjs/platform-express';
import { AppService } from './app.service';
// some code hidden for display purpose
@Controller()
export class AppController {
  constructor(private readonly appService: AppService) {}


  @Get('read-image')
  @Header('Content-Type','image/webp')
  async readImage(@Res() res,@Query('filename') filename){
    const file = await this.appService.getfileStream(filename);
    return file.pipe(res);
  }
}

• (Line: 11) '@Header()' decorator used to specify the 'Content-Type' and its value 'image/webp'(webp is image format like jpg, png, webp, etc). Because of this header value, the image stream going to be rendered on the browser.
• (Line: 12) '@Res()' decorator is response object. '@Query()' decorator to capture query params.
• (Line: 13-14) After getting the file stream from Azure Blob Storage, we are flushing the stream into the response object.

Now try to access this new endpoint and check the result.

Create NestJS Endpoint To Download Image:

The new endpoint on opening it on a browser it's going to download the image from the Azure blob storage.

So logic to download image same as the read image endpoint just we created above, the only difference we need to add a one addition header decorator here.

src/app.controller.cs:

@Get('download-image')
@Header('Content-Type','image/webp')
@Header('Content-Disposition', 'attachment; filename=test.webp')
async downloadImage(@Res() res,@Query('filename') filename){
    const file = await this.appService.getfileStream(filename);
    return file.pipe(res);
}

(Line: 3) This header 'Content-Disposition' and its value 'attachment' makes the browser understand that response should be downloaded.

Create NestJS Endpoint To Delete Image:

The new endpoint going to delete the files from the Azure blob storage.

src/app.service.ts:

async delete(filename: string){
 const blobClient = this.getBlobClient(filename);
 await blobClient.deleteIfExists();
}

• The 'deleteIfExists' method going to delete the file if exists on the Azure blob storage.

src/app.controller.ts:

@Get('delete-image')
async delete(@Query('filename') filename){
 await this.appService.delete(filename);
 return "deleted";
}

That's all about file operation in Azure Blob Storage from the NestJS application.

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Wrapping Up:

Hopefully, I think this article delivered some useful information about NestJS API file operations using Azure Blob Storage. I love to have your feedback, suggestions, and better techniques in the comment section below.

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