Using multipart/form-data in Nestjs - nestjs

Question

I have a requirement of uploading a pdf file to the a third-party API to do that what we are using a controller and then sending its buffer to the endpoint in multipart/form-data but It's not working. What am i doing wrong??
I have my controller defined like
#Post('/upload')
#UseInterceptors(FileInterceptor('file'))
async uploadDocument(#UploadedFile() file: Express.Multer.File){
await this.httpRequestService.uploadDocument(file)
return [
Translation.translate('Create_Success_Message', {
Entity: 'File'
}),
{
file
}
]
}
This controller calls a service called uploadDocument which looks like:
async uploadDocument(file){
try{
const formData = new FormData()
formData.append('file', file)
const response = await this.httpService.post(`urlWhereItHits`,
formData,
{
headers:{
"X-AppSecretToken":"appsecrettoken",
"X-AgreementGrantToken":"agreementgranttoken",
'Content-Type' : 'multipart/form-data'
},
}).toPromise();
}
catch(error){
console.log(error)
}
}
Now i don't understand what's happening wrong here.
I get error saying
TypeError: source.on is not a function at Function.DelayedStream.create (C:\Users\Tushar\Squire-backend\node_modules\delayed-stream\lib\delayed_stream.js:33:10)

Answer 1

I had a similar task, receiving a .csv file and sending it to another server.
controller:
#UseInterceptors(FileInterceptor('file'))
#Post('upload')
async uploadFile(#UploadedFile() file: Express.Multer.File) {
await this.myService.uploadFile(file);
return {
message: 'File uploaded successfully.',
};
}
service:
import * as FormData from 'form-data';
import { Readable } from 'stream';
async uploadFile(file: Express.Multer.File) {
const form = new FormData();
form.append('files', Readable.from(file.buffer), {
filename: file.originalname,
});
try {
const result = await lastValueFrom(
this.httpService.post('The URL of your third-party service', form, {
headers: {
...form.getHeaders(),
},
}),
);
if (result.status === 200) return;
} catch {
throw new InternalServerErrorException(
'Error while uploading the .csv file.',
);
}
}
Some explanations here:
It requires importing Formdata from the package.
.append() requires a fieldName, and a readable Stream.
You can use the buffer of the file that's on memory (not recommended with large files) and use it to create a readable stream.
Also, you need to add the name of the file manually since Formdata only recognizes the filename if the file is saved on disk. (Which in our case is on memory as a Buffer).
You can create the stream in different ways, the example is not mandatory.
.getHeaders() will generate the default header 'Content-Type': 'multipart/form-data' and also it will generate the boundary of the file, like this: reference
{
'content-type': 'multipart/form-data; boundary=--------------------------286308325485491440714225'
}