public void test_getAccessTokenFromRequest_ok0() {
        final String token = accessTokenHelper.generateAccessToken();
        MockletHttpServletRequest req = getMockRequest();
        req.addHeader("Authorization", "Bearer " + token);
        assertEquals(token, accessTokenHelper.getAccessTokenFromRequest(req));
    }

    public void test_getAccessTokenFromRequest_ok1() {
        final String token = accessTokenHelper.generateAccessToken();

    * But it needs authentication for that specific endpoint.
    * So, to authenticate with our API, it sends a header `Authorization` with a value of `Bearer ` plus the token.
    * If the token contains `foobar`, the content of the `Authorization` header would be: `Bearer foobar`.

## **FastAPI**'s `OAuth2PasswordBearer`

    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid authentication credentials",
            headers={"WWW-Authenticate": "Bearer"},
        )
    return user


async def get_current_active_user(
    current_user: Annotated[User, Depends(get_current_user)],
):
    if current_user.disabled:

    * Но для этого необходима аутентификация для конкретной конечной точки.
    * Поэтому для аутентификации в нашем API он посылает заголовок `Authorization` со значением `Bearer` плюс сам токен.
    * Если токен содержит `foobar`, то содержание заголовка `Authorization` будет таким: `Bearer foobar`.

## Класс `OAuth2PasswordBearer` в **FastAPI**

    - 为指定的端点（Endpoint）进行身份验证
    - 因此，用 API 验证身份时，要发送值为 `Bearer` + 令牌的请求头 `Authorization`
    - 假如令牌为 `foobar`，`Authorization` 请求头就是： `Bearer foobar`

## **FastAPI** 的 `OAuth2PasswordBearer`

**FastAPI** 提供了不同抽象级别的安全工具。

本例使用 **OAuth2** 的 **Password** 流以及 **Bearer** 令牌（`Token`）。为此要使用 `OAuth2PasswordBearer` 类。

!!! info "说明"

    `Bearer` 令牌不是唯一的选择。

    但它是最适合这个用例的方案。

OpenAPI defines the following security schemes:

* `apiKey`: an application specific key that can come from:
    * A query parameter.
    * A header.
    * A cookie.
* `http`: standard HTTP authentication systems, including:
    * `bearer`: a header `Authorization` with a value of `Bearer ` plus a token. This is inherited from OAuth2.
    * HTTP Basic authentication.
    * HTTP Digest, etc.

OpenAPI define os seguintes esquemas de segurança:

* `apiKey`: uma chave específica de aplicação que pode vir de:
    * Um parâmetro query.
    * Um header.
    * Um cookie.
* `http`: padrão HTTP de sistemas autenticação, incluindo:
    * `bearer`: um header de `Authorization` com valor de `Bearer` adicionado de um token. Isso é herança do OAuth2.
    * HTTP Basic authentication.
    * HTTP Digest, etc.

            headers={"WWW-Authenticate": "Bearer"},
        )
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username}, expires_delta=access_token_expires
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(

	// already present we can blindly use the
	// authToken as is instead of adding 'Bearer'
	tokens := strings.Fields(target.args.AuthToken)
	switch len(tokens) {
	case 2:
		req.Header.Set("Authorization", target.args.AuthToken)
	case 1:
		req.Header.Set("Authorization", "Bearer "+target.args.AuthToken)
	}

	req.Header.Set("Content-Type", "application/json")

	return target.httpClient.Do(req)
}

    ```

!!! info
    The additional header `WWW-Authenticate` with value `Bearer` we are returning here is also part of the spec.

    Any HTTP (error) status code 401 "UNAUTHORIZED" is supposed to also return a `WWW-Authenticate` header.

    In the case of bearer tokens (our case), the value of that header should be `Bearer`.

    You can actually skip that extra header and it would still work.