Uploading binary file (buffer) using NestJS

file-buffer-nestjs.ts

// Had to upload a binary file but multer only works with `multipart/form-data`
// And NestJS parses the request. So I had to manually upload it.
// First in `main.ts` I had to edit the following line:

const app = await NestFactory.create(AppModule);

// For: 

const app = await NestFactory.create(AppModule, { bodyParser: false });

// So NestJS allows us to handle the request.
// The next step is to create a Middleware, I named it `FileBufferMiddleware`
// I added the following content:

import { Injectable, NestMiddleware } from '@nestjs/common';
import { raw } from 'body-parser';

@Injectable()
export class FileBufferMiddleware implements NestMiddleware {
  use(req: any, res: any, next: () => void): any {
    raw({
      verify: (req, res, buffer) => {
        req['fileBuffer'] = buffer;
      },
      limit: '5mb',
    })(req, res as any, next);
  }
}

// We need to add to our `MiddlewareModule` like so:

export class MiddlewareModule implements NestModule {
  configure(consumer: MiddlewareConsumer) {
    consumer
      .apply(FileBufferMiddleware)
      .forRoutes({
        path: '/upload/:fileName',
        method: RequestMethod.PUT,
      });
  }
}

// With that we will have a `fileBuffer` which is a Buffer object in the request.
// And to make it even easier, I also created a decorator named `FileBuffer`:

import { createParamDecorator, ExecutionContext } from '@nestjs/common';

export const FileBuffer = createParamDecorator(
  (data: unknown, ctx: ExecutionContext) => {
    const request = ctx.switchToHttp().getRequest();

    return request.fileBuffer || null;
  },
);

// So, we can just use the decorator in the Controller and we will already have the object ready to manipulate:
@Put('/upload/:fileName')
  upload(
    @Res() response: Response,
    @Param() fileName: string,
    @FileBuffer() fileBuffer,
  ): object {
    if (fileBuffer === null) throw new BadRequestException('File is required');

    const writeStream = createWriteStream(`./data/${fileName}`);
    writeStream.write(fileBuffer);

    return response
      .status(HttpStatus.CREATED)
      .send({ HttpCode: 201, Message: 'File uploaded.' });
  }

// And that's it, now we have an upload using a binary file.

@MastalerzKamil Yes, there's a way to test it, it's very simple, in Postman you must send a request of type Put to the endpoint /upload/filename.png, and then in the Body of the request mark the type as binary and then use the Select File button and select the file you want to upload to the API, see the image:

Using Insomnia is even simpler, you should send a Put request to the /upload/filename.png endpoint, then in the Body of the request select Binary File and in the field SELECTED FILE click and select the file you want to upload and then test, see the image:

Just in case somebody wants to keep the old behavior for some routes, this a really cool article that walks you through: https://www.darraghoriordan.com/2021/06/20/parse-request-raw-body-nest-js-controller/

Thanks for this.

One thing to note: for me I kept on getting the BadRequestException until I added the following line to the raw functions options:

type: image/jpeg