A middleware doesn't have to be made for FastAPI or Starlette to work, as long as it follows the ASGI spec.

In general, ASGI middlewares are classes that expect to receive an ASGI app as the first argument.

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

But let's save you the time of reading the full long specification just to find those little pieces of information you need.

Let's use the tools provided by **FastAPI** to handle security.

## How it looks

    "W",  # pycodestyle warnings
    "F",  # pyflakes
    "I",  # isort
    "B",  # flake8-bugbear
    "C4",  # flake8-comprehensions
    "UP",  # pyupgrade
]
ignore = [
    "E501",  # line too long, handled by black
    "B008",  # do not perform function calls in argument defaults
    "C901",  # too complex
    "W191",  # indentation contains tabs
]

[tool.ruff.lint.per-file-ignores]

{% for section_name, section_content in external_links.items() %}

## {{ section_name }}

{% for lang_name, lang_content in section_content.items() %}

### {{ lang_name }}

{% for item in lang_content %}

.idea
.ipynb_checkpoints
.mypy_cache
.vscode
__pycache__
.pytest_cache
htmlcov
dist
site
.coverage
coverage.xml
.netlify
test.db
log.txt
Pipfile.lock
env3.*
env
docs_build
site_build
venv
docs.zip
archive.zip

# vim temporary files
*~
.*.sw?
.cache

# macOS

**FastAPI** は、それぞれの場合の処理​​方法と同じオブジェクトの再利用方法を知っているため、すべてのバックグラウンドタスクがマージされ、バックグラウンドで後で実行されます。

```Python hl_lines="13  15  22  25"
{!../../../docs_src/background_tasks/tutorial002.py!}
```

この例では、レスポンスが送信された *後* にメッセージが `log.txt` ファイルに書き込まれます。

リクエストにクエリがあった場合、バックグラウンドタスクでログに書き込まれます。

そして、*path operations 関数* で生成された別のバックグラウンドタスクは、`email` パスパラメータを使用してメッセージを書き込みます。

## 技術的な詳細

Do you want to just have a `str`? Or just a `dict`? Or a database class model instance directly? It all works the same way.

You actually don't have users that log in to your application but robots, bots, or other systems, that have just an access token? Again, it all works the same.

---

Another useful case is when you want to have keys of another type (e.g., `int`).

That's what we are going to see here.

In this case, you would accept any `dict` as long as it has `int` keys with `float` values:

=== "Python 3.9+"

    ```Python hl_lines="7"
    {!> ../../../docs_src/body_nested_models/tutorial009_py39.py!}
    ```

=== "Python 3.8+"

    ```

=== "Python 3.8+"

    ```Python hl_lines="20-21"
    {!> ../../../docs_src/path_operation_configuration/tutorial003.py!}
    ```

## Description from docstring

Or you might have any other way to communicate with the WebSocket endpoint.

---

But for this example, we'll use a very simple HTML document with some JavaScript, all inside a long string.

This, of course, is not optimal and you wouldn't use it for production.

In production you would have one of the options above.