Uploading Files to Amazon S3 Bucket in NestJs using File Buffer.

Upload Files to Amazon S3 Bucket using NestJs

Amazon Simple Storage Service (S3) is an object storage service that offers industry-leading scalability, data availability, security, and performance. In this tutorial, we will learn how to use NestJS to upload files to an S3 bucket.

Prerequisites

• Node.js and npm installed on your machine
• An AWS account
• A Bucket created in your AWS S3

Setting up the project

Let’s start by creating a new NestJS project:

$ npm init nest-app file-upload-project
$ cd file-upload-project

Next, install the required dependencies:

$ npm install --save aws-sdk
$ npm install --save @nestjs/common @nestjs/core @nestjs/platform-express rxjs

Creating the S3 service

/** Uploading file to S3 and saving the file and file url in users document **/
  async uploadFile(body: { file: Buffer, userId: string }) {
    /** Generates a 4 digit random integer */
    const generateRandomNumber = Math.floor(1000 + Math.random() * 9000);
    const fileContent = Buffer.from(body.file.buffer);
    /** Uploading the file to S3 Bucket */
    const s3 = new AWS.S3();
    const uploadResult = await s3.upload({
      Bucket: process.env.AWS_BUCKET_NAME,
      Body: fileContent,
      Key: `${generateRandomNumber}-${body.userId['userId']}-${body.file['originalname']}`,
    }).promise() /** It returns the file key (file name) and file location */
    /** Updating the user document by id - setting s3 file url */
    return this.userModel.findByIdAndUpdate(body.userId['userId'], {
      fileUrl: uploadResult.Location,
    })
  }

In the code above, we are using the AWS SDK to create a new S3 client and define an upload method that accepts a buffer, a bucket name, and a key (the file name). The method returns a promise that resolves to the URL of the uploaded file.

Don’t forget to replace your-access-key-id and your-secret-access-key with your own AWS credentials.

Creating the controller

Now let’s create a controller that will handle the file upload. In the src directory, create a new file called upload.controller.ts and add the following code:

 @Post('upload/file')
  @UseInterceptors(FileInterceptor('file'))
  uploadFile(
      @UploadedFile() file: any,
      @Body() userId: string,
      @Res() res: Response,
  ) {
    /** Checking file size in bytes - if it's greater than 1MB then throws error */
    if (file['size'] > 1000000) {
      throw new NotAcceptableException; // throw error.
    }
    /** Checking file type - Here I'm allowing to upload CSV, XLS, XLSX*/
    if (!((file['mimetype'] === 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet') || (file['mimetype'] === 'application/vnd.ms-excel') || (file['mimetype'] === 'text/csv'))) {
      throw new NotAcceptableException; // throw error.
    }
    return this.service.uploadFile(file, userId);
  }

Setup for Postman

• Select request method as POST
• Select Body and form-data
• And then select type as file

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