## 常规 **FastAPI** 应用

添加回调前，首先看下常规 API 应用是什么样子。

常规 API 应用包含接收 `Invoice` 请求体的*路径操作*，还有包含回调 URL 的查询参数 `callback_url`。

这部分代码很常规，您对绝大多数代码应该都比较熟悉了：

{* ../../docs_src/openapi_callbacks/tutorial001.py hl[10:14,37:54] *}

/// tip | 提示

`callback_url` 查询参数使用 Pydantic 的 <a href="https://pydantic-docs.helpmanual.io/usage/types/#urls" class="external-link" target="_blank">URL</a> 类型。

///

app = FastAPI()

callback_router = APIRouter(default_response_class=JSONResponse)


@callback_router.get(
    "{$callback_url}/callback/", responses={400: {"model": CustomModel}}
)
def callback_route():
    pass  # pragma: no cover


@app.post("/", callbacks=callback_router.routes)
def main_route(callback_url: HttpUrl):
    pass  # pragma: no cover


client = TestClient(app)


def test_openapi_schema():

@invoices_callback_router.post(
    "{$callback_url}/invoices/{$request.body.id}", response_model=InvoiceEventReceived
)
def invoice_notification(body: InvoiceEvent):
    pass  # pragma: nocover


class Event(BaseModel):
    name: str
    total: float


events_callback_router = APIRouter()


@events_callback_router.get("{$callback_url}/events/{$request.body.title}")
def event_callback(event: Event):

Tendrá una *path operation* que recibirá un cuerpo `Invoice`, y un parámetro de query `callback_url` que contendrá la URL para el callback.

Esta parte es bastante normal, probablemente ya estés familiarizado con la mayor parte del código:

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[7:11,34:51] *}

/// tip | Consejo

В нём будет *операция пути*, которая получит тело запроса `Invoice`, и query-параметр `callback_url`, содержащий URL для обратного вызова.

Эта часть вполне обычна, большая часть кода вам уже знакома:

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[7:11,34:51] *}

/// tip | Совет

Dieser Teil ist ziemlich normal, der größte Teil des Codes ist Ihnen wahrscheinlich bereits bekannt:

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[7:11,34:51] *}

/// tip | Tipp

invoices_callback_router = APIRouter()


@invoices_callback_router.post(
    "{$callback_url}/invoices/{$request.body.id}", response_model=InvoiceEventReceived
)
def invoice_notification(body: InvoiceEvent):
    pass


@app.post("/invoices/", callbacks=invoices_callback_router.routes)
def create_invoice(invoice: Invoice, callback_url: HttpUrl | None = None):
    """
    Create an invoice.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[7:11,34:51] *}

/// tip

Ele terá uma *operação de rota* que receberá um corpo `Invoice`, e um parâmetro de consulta `callback_url` que conterá a URL para o callback.

Essa parte é bastante normal, a maior parte do código provavelmente já é familiar para você:

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[7:11,34:51] *}

/// tip | Dica

                                    {"type": "null"},
                                ],
                                "title": "Callback Url",
                            },
                            "name": "callback_url",
                            "in": "query",
                        }
                    ],
                    "requestBody": {
                        "content": {
                            "application/json": {