To create the callback *path operation* use the same `APIRouter` you created above.

It should look just like a normal FastAPI *path operation*:

* It should probably have a declaration of the body it should receive, e.g. `body: InvoiceEvent`.
* And it could also have a declaration of the response it should return, e.g. `response_model=InvoiceEventReceived`.

```Python hl_lines="16-18  21-22  28-32"

首先，新建包含一些用于回调的 `APIRouter`。

```Python hl_lines="5  26"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

### 创建回调*路径操作*

创建回调*路径操作*也使用之前创建的 `APIRouter`。

它看起来和常规 FastAPI *路径操作*差不多：

* 声明要接收的请求体，例如，`body: InvoiceEvent`
* 还要声明要返回的响应，例如，`response_model=InvoiceEventReceived`

```Python hl_lines="17-19  22-23  29-33"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

回调*路径操作*与常规*路径操作*有两点主要区别：

```
https://www.external.org/events/invoices/2expen51ve
```

mit einem JSON-Body, der etwa Folgendes enthält:

```JSON
{
    "description": "Payment celebration",
    "paid": true
}
```

und sie würde eine Response von dieser *externen API* mit einem JSON-Body wie dem folgenden erwarten:

```JSON
{
    "ok": true
}
```

!!! tip "Tipp"

```Python hl_lines="3  25"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

### ✍ ⏲ *➡ 🛠️*

✍ ⏲ *➡ 🛠️* ⚙️ 🎏 `APIRouter` 👆 ✍ 🔛.

⚫️ 🔜 👀 💖 😐 FastAPI *➡ 🛠️*:

* ⚫️ 🔜 🎲 ✔️ 📄 💪 ⚫️ 🔜 📨, ✅ `body: InvoiceEvent`.
*  & ⚫️ 💪 ✔️ 📄 📨 ⚫️ 🔜 📨, ✅ `response_model=InvoiceEventReceived`.

```Python hl_lines="16-18  21-22  28-32"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```