Remove default `application/json` header from fastapi response

Question

I have taken this (https://fastapi.tiangolo.com/advanced/response-directly/#returning-a-custom-response) example from fastapi documentation regarding how to return a custom response from a fastapi application. This is my example code that i came up with to test it :

from http.client import responses
from fastapi import FastAPI, Response

app = FastAPI()

response_examples = {
    200: {
        "description": "Success",
        "content": {
            "application/xml": {
                "example": {
                    """<?xml version="1.0"?>
    <shampoo>
    <Header>
        Apply shampoo here.
    </Header>
    <Body>
        You'll have to use soap here.
    </Body>
    </shampoo>
    """
                }
            }
        },
    },
    400: {"description": "An invalid value for header content-type."},
    405: {"description": "Endpoint only supports POST."},
    500: {"description": "Internal server error."},
}


@app.get("/legacy/", responses=response_examples)
def get_legacy_data():
    data = """<?xml version="1.0"?>
    <shampoo>
    <Header>
        Apply shampoo here.
    </Header>
    <Body>
        You'll have to use soap here.
    </Body>
    </shampoo>
    """
    return Response(content=data, media_type="application/xml")

However my question is regarding the open api file when I am querying the /docs endpoint of my application.

Below is the relevant section of the /docs endpoint response(in yaml):

openapi: 3.0.2
info:
  title: FastAPI
  version: 0.1.0
paths:
  /legacy/:
    get:
      summary: Get Legacy Data
      operationId: get_legacy_data_legacy__get
      responses:
        '200':
          description: Success
          content:
            application/json:
              schema: {}
            application/xml:
              example:
                - |-
                  <?xml version="1.0"?>
                      <shampoo>
                      <Header>
                          Apply shampoo here.
                      </Header>
                      <Body>
                          You'll have to use soap here.
                      </Body>
                      </shampoo>
                      
        '400':
          description: An invalid value for header content-type.
        '405':
          description: Endpoint only supports POST.
        '500':
          description: Internal server error.

There are 2 header types mentioned in the response application/json and application/xml which is the right response header. There should not be an application/json response at all.

My question is that is this possible to do in fastapi and if so how can i remove the default application/json header from response.

Asked By: Subhayan Bhattacharya

||

Source

Answer 1

You should put in a response_class= parameter in your endpoint. Below is a fully working example:

from fastapi import FastAPI, Response

app = FastAPI()

response_examples = {
    200: {
        "description": "Success",
        "content": {
            "application/xml": {
                "example": {
                    """<?xml version="1.0"?>
    <shampoo>
    <Header>
        Apply shampoo here.
    </Header>
    <Body>
        You'll have to use soap here.
    </Body>
    </shampoo>
    """
                }
            }
        },
    },
    400: {"description": "An invalid value for header content-type."},
    405: {"description": "Endpoint only supports POST."},
    500: {"description": "Internal server error."},
}

class XMLResponse(Response):
    media_type = "application/xml"



@app.get("/legacy/", responses=response_examples, response_class=XMLResponse)
def get_legacy_data():
    data = """<?xml version="1.0"?>
    <shampoo>
    <Header>
        Apply shampoo here.
    </Header>
    <Body>
        You'll have to use soap here.
    </Body>
    </shampoo>
    """
    return XMLResponse(content=data)

if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8000,  )

The outcome:

Answered By: JarroVGIT

Remove default `application/json` header from fastapi response

Question:

Answers: