NestJS returning the result of an HTTP request

Question

In my NestJS application I want to return the result of an http call.

Following the example of the NestJS HTTP module, what I'm doing is simply:

import { Controller, HttpService, Post } from '@nestjs/common';
import { AxiosResponse } from '@nestjs/common/http/interfaces/axios.interfaces';
import { Observable } from 'rxjs/internal/Observable';

@Controller('authenticate')
export class AuthController {

  constructor(private readonly httpService: HttpService) {}

  @Post()
  authenticate(): Observable<AxiosResponse<any>> {
    return this.httpService.post(...);
  }
}

However from the client I'm getting 500 and the server console is saying:

TypeError: Converting circular structure to JSON at JSON.stringify () at stringify (/Users/francesco.borzi/sources/business-controller-rewrite/node_modules/express/lib/response.js:1119:12) at ServerResponse.json (/Users/francesco.borzi/sources/business-controller-rewrite/node_modules/express/lib/response.js:260:14) at ExpressAdapter.reply (/Users/francesco.borzi/sources/business-controller-rewrite/node_modules/@nestjs/core/adapters/express-adapter.js:41:52) at RouterResponseController.apply (/Users/francesco.borzi/sources/business-controller-rewrite/node_modules/@nestjs/core/router/router-response-controller.js:11:36) at at process._tickCallback (internal/process/next_tick.js:182:7)

Maybe httpService return some non-valid JSON, and NestJS (Express) throw the error because cannot convert. Try call something simple with httpService, maybe simple test GET. — Vladyslav Moisieienkov, May 16 '18 at 07:58
from what is my understanding, NestJS should automatically convert to json.. am I right? — Francesco Borzi, May 16 '18 at 08:01
As I'm experiencing the same exact thing, I tried testing with another source that I'm 100% positive is returning valid json and it's still giving the same error. Same result when using GET. — andyrue, May 16 '18 at 12:21

score 56 · Accepted Answer · edited May 16 '18 at 20:56

56

This issue comes from the axios library. In order to fix that, you have to pull out the data property:

return this.httpService.post(...)
  .pipe(
    map(response => response.data),
  );

edited May 16 '18 at 20:56

Francesco Borzi

56,083
47
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answered May 16 '18 at 13:30

Kamil Myśliwiec

8,548
2
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33

2

So I had to learn this on my on. But now I want to push the original HTTP Status code in the case of an error. Any tips? – Sani Yusuf Aug 03 '18 at 00:03
Thanks a lot, this isn't fixed as of today – Adam Soto Oct 01 '20 at 10:56

andyrue · Answer 2 · 2022-01-12T16:07:31.140

11

The problem seems to stem from the fact that we are trying to return a Response object directly, and that is circular by nature. I'm not sure of the correct way to implement this, but I was able to get around it by using axios directly, unwrapping the promise and returning just the data.

@Post('login')
  async authenticateUser(@Body() LoginDto) {
    const params = JSON.stringify(LoginDto);

    return await axios.post('https://api.example.com/authenticate_user',
      params,
      {
        headers: {
          'Content-Type': 'application/json',
        },
      }).then((res) => {
          return res.data;
    });
}

UPDATE

I realized I could just do the same thing to the Observable being returned from the httpService using the new rxjs pipe method, so that's probably the better way to do it.

@Post('login')
async authenticateUser(@Body() LoginDto) {
    const params = JSON.stringify(LoginDto);

    return this.httpService.post('https://api.example.com/authenticate_user',
      params,
      {
        headers: {
          'Content-Type': 'application/json',
        },
      }).pipe(map((res) => {
    return res.data;
  }));
}

edited Jan 12 '22 at 16:07

answered May 16 '18 at 13:22

andyrue

903
10
24

1

@andyrune. Sorry , I just wanted to point out that async await doesn't work with Observables. It works only with promises. I believe you have to convert your observable to a promise and then use async/await. – vijayakumarpsg587 Feb 25 '19 at 11:22
@andyrune, why controller here, make api call and hit another api instead of directly return data from database? – Muhammed Moussa May 07 '19 at 11:50
2

@MuhammedMoussa In my case the authentication api is on a different server. – andyrue May 07 '19 at 20:04
1

This works, but is really ugly imo. Why is making http request implemented in such a weird way? – fonzane Aug 16 '21 at 13:04
I am not getting any response, when I tried to console.log the response – AbhimanuSharma Aug 23 '21 at 11:40

score 0 · Answer 3 · answered Jun 15 '22 at 05:28

If you are looking for HTTP Data, HTTP Status code and wanted to convert an observable to a promise using firstValueFrom ('rxjs')

const responseData = await firstValueFrom(
        this.httpService.post(url, data, config).pipe(map((response) => [response.data, response.status])),
      );

score 0 · Answer 4 · answered May 28 '23 at 20:52

0

For those of us who are familiar with Axios and want to stick to that, here's the solution I can suggest:

@Injectable()
export class HttpService {
 constructor(private readonly http: HttpService){}

 fetch(url, params) {
  return this.http.axiosRef.get(url, params)
  }

}

answered May 28 '23 at 20:52

giles

85
1
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HttpService class is imported from @nestjs/axios – giles May 28 '23 at 20:53

NestJS returning the result of an HTTP request

4 Answers4