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.

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