## Mounting a **FastAPI** application { #mounting-a-fastapi-application }

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

### Top-level application { #top-level-application }

                            "description": "Successful Response",
                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {

                            "description": "Successful Response",
                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools" package="okhttp.android.testapp">

  <uses-permission android:name="android.permission.INTERNET" />

  <application
    android:allowBackup="true"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:name=".TestApplication"
  >
    <activity
      android:name=".MainActivity"

                            "200": {
                                "description": "Successful Response",
                                "content": {
                                    "application/json": {
                                        "schema": {"$ref": "#/components/schemas/Token"}
                                    }
                                },
                            },

                            "description": "Successful Response",
                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {

from fastapi.testclient import TestClient


class ORJSONResponse(JSONResponse):
    media_type = "application/x-orjson"

    def render(self, content: Any) -> bytes:
        return orjson.dumps(content)


class OverrideResponse(JSONResponse):
    media_type = "application/x-override"


app = FastAPI(default_response_class=ORJSONResponse)
router_a = APIRouter()
router_a_a = APIRouter()

                            "description": "Successful Response",
                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {

                                "application/json": {
                                    "schema": {},
                                },
                            },
                            "description": "Successful Response",
                        },
                        "422": {
                            "content": {
                                "application/json": {

                            "description": "Successful Response",
                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {