در صورت وجود هر گونه وظایف پس زمینه (که در ادامه توضیح داده می‌شوند)، تمام میان‌افزارها *پس از آن* اجرا خواهند شد.

///

## ساخت یک میان افزار

برای ایجاد یک میان‌افزار، از دکوریتور `@app.middleware("http")` در بالای یک تابع استفاده می‌شود.

تابع میان افزار دریافت می کند:
* `درخواست`
* تابع `call_next` که `درخواست` را به عنوان پارامتر دریافت می کند
    * این تابع `درخواست` را به *path operation* مربوطه ارسال می کند.

///

対話的APIドキュメントは複数の値を許可するために自動的に更新されます。

<img src="https://fastapi.tiangolo.com/img/tutorial/query-params-str-validations/image02.png">

### デフォルト値を持つ、クエリパラメータのリスト / 複数の値

また、値が指定されていない場合はデフォルトの`list`を定義することもできます。

{* ../../docs_src/query_params_str_validations/tutorial012.py hl[9] *}

以下のURLを開くと:

```
http://localhost:8000/items/
```

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