Because of this, **FastAPI** itself provides an alternative API documentation (using ReDoc), which you can access at <a href="http://127.0.0.1:8000/redoc" class="external-link" target="_blank">http://127.0.0.1:8000/redoc</a>:

<img src="/img/tutorial/path-params/image02.png">

* `allow_credentials` - 指示跨域请求支持 cookies。默认是 `False`。另外，允许凭证时 `allow_origins` 不能设定为 `['*']`，必须指定源。
* `expose_headers` - 指示可以被浏览器访问的响应头。默认为 `[]`。
* `max_age` - 设定浏览器缓存 CORS 响应的最长时间，单位是秒。默认为 `600`。

中间件响应两种特定类型的 HTTP 请求……

### CORS 预检请求

这是些带有 `Origin` 和 `Access-Control-Request-Method` 请求头的 `OPTIONS` 请求。

* `allow_methods` - 교차-출처 요청을 허용하는 HTTP 메소드의 리스트입니다. 기본값은 `['GET']` 입니다. `['*']` 을 사용하여 모든 표준 메소드들을 허용할 수 있습니다.
* `allow_headers` - 교차-출처를 지원하는 HTTP 요청 헤더의 리스트입니다. 기본값은 `[]` 입니다. 모든 헤더들을 허용하기 위해 `['*']` 를 사용할 수 있습니다. `Accept`, `Accept-Language`, `Content-Language` 그리고 `Content-Type` 헤더는 CORS 요청시 언제나 허용됩니다.
* `allow_credentials` - 교차-출처 요청시 쿠키 지원 여부를 설정합니다. 기본값은 `False` 입니다. 또한 해당 항목을 허용할 경우 `allow_origins` 는 `['*']` 로 설정할 수 없으며, 출처를 반드시 특정해야 합니다.

* Headers.
* Cookies.
* etc.

And by doing so, **FastAPI** is validating that data, converting it and generating documentation for your API automatically.

But there are situations where you might need to access the `Request` object directly.

## Details about the `Request` object

* `allow_methods` - オリジン間リクエストで許可するHTTPメソッドのリスト。デフォルトは `['GET']` です。`['*']`を使用してすべての標準メソッドを許可できます。
* `allow_headers` - オリジン間リクエストでサポートするHTTPリクエストヘッダーのリスト。デフォルトは `[]` です。`['*']`を使用して、すべてのヘッダーを許可できます。CORSリクエストでは、 `Accept` 、 `Accept-Language` 、 `Content-Language` 、 `Content-Type` ヘッダーが常に許可されます。
* `allow_credentials` - オリジン間リクエストでCookieをサポートする必要があることを示します。デフォルトは `False` です。
* `expose_headers` - ブラウザからアクセスできるようにするレスポンスヘッダーを示します。デフォルトは `[]` です。

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.

Just use any kind of model, any kind of class, any kind of database that you need for your application. **FastAPI** has you covered with the dependency injection system.

## Code size

Create a variable for the expiration of the token.

Define a Pydantic Model that will be used in the token endpoint for the response.

Create a utility function to generate a new access token.

=== "Python 3.10+"

    ```Python hl_lines="6  12-14  28-30  78-86"
    {!> ../../../docs_src/security/tutorial004_an_py310.py!}
    ```

=== "Python 3.9+"

@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(

@app.post("/token")
async def login_for_access_token(
    form_data: Annotated[OAuth2PasswordRequestForm, Depends()],
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(

    obtain the OAuth2 scopes required by all the dependencies in the same chain.

    This way, multiple dependencies can have different scopes, even when used in the
    same *path operation*. And with this, you can access all the scopes required in
    all those dependencies in a single place.

    Read more about it in the
    [FastAPI docs for OAuth2 scopes](https://fastapi.tiangolo.com/advanced/security/oauth2-scopes/).
    """