app = FastAPI()


class InternalError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except InternalError:
        print("Oops, we didn't raise again, Britney 😱")


@app.get("/items/{item_id}")
def get_item(item_id: str, username: Annotated[str, Depends(get_username)]):
    if item_id == "portal-gun":
        raise InternalError(

        });

    }

    public void changePassword(final String username, final String password) {
        final boolean changed = ComponentUtil.getAuthenticationManager().changePassword(username, password);
        if (changed) {
            userBhv.selectEntity(cb -> cb.query().setName_Equal(username)).ifPresent(entity -> {
                final String encodedPassword = fessLoginAssist.encryptPassword(password);

```Python
UserInDB(**user_dict)
```

就会生成如下结果：

```Python
UserInDB(
    username="john",
    password="secret",
    email="******@****.***",
    full_name=None,
)
```

或更精准，直接把可能会用到的内容与 `user_dict` 一起使用：

```Python
UserInDB(
    username = user_dict["username"],
    password = user_dict["password"],
    email = user_dict["email"],
    full_name = user_dict["full_name"],

    assert response.json() == {"detail": "Incorrect username or password"}


@needs_py310
def test_login_incorrect_username(client: TestClient):
    response = client.post("/token", data={"username": "foo", "password": "secret"})
    assert response.status_code == 400, response.text
    assert response.json() == {"detail": "Incorrect username or password"}


@needs_py310
def test_no_token(client: TestClient):

        validatePasswordForm(form, toIndexPage);
        final String username = getUserBean().map(FessUserBean::getUserId).get();
        try {
            userService.changePassword(username, form.newPassword);
            saveInfo(messages -> messages.addSuccessChangedPassword(GLOBAL));
        } catch (final Exception e) {
            logger.warn("Failed to change password for {}", username, e);

本章添加上一章示例中欠缺的部分，实现完整的安全流。

## 获取 `username` 和 `password`

首先，使用 **FastAPI** 安全工具获取 `username` 和 `password`。

OAuth2 规范要求使用**密码流**时，客户端或用户必须以表单数据形式发送 `username` 和 `password` 字段。

并且，这两个字段必须命名为 `username` 和 `password` ，不能使用 `user-name` 或 `email` 等其它名称。

不过也不用担心，前端仍可以显示终端用户所需的名称。

数据库模型也可以使用所需的名称。

但对于登录*路径操作*，则要使用兼容规范的 `username` 和 `password`，（例如，实现与 API 文档集成）。

该规范要求必须以表单数据形式发送 `username` 和 `password`，因此，不能使用 JSON 对象。

                """
            ),
        ] = None,
        username: Annotated[
            str,
            Form(),
            Doc(
                """
                `username` string. The OAuth2 spec requires the exact field name
                `username`.
                """
            ),
        ],
        password: Annotated[
            str,

UserInDB(**user_dict)
```

dann ist das ungefähr äquivalent zu:

```Python
UserInDB(
    username="john",
    password="secret",
    email="******@****.***",
    full_name=None,
)
```

Oder, präziser, `user_dict` wird direkt verwendet, welche Werte es auch immer haben mag:

```Python
UserInDB(
    username = user_dict["username"],
    password = user_dict["password"],
    email = user_dict["email"],

app = FastAPI()

security = HTTPBasic()


def get_current_username(
    credentials: Annotated[HTTPBasicCredentials, Depends(security)],
):
    current_username_bytes = credentials.username.encode("utf8")
    correct_username_bytes = b"stanleyjobson"
    is_correct_username = secrets.compare_digest(
        current_username_bytes, correct_username_bytes
    )
    current_password_bytes = credentials.password.encode("utf8")

        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None: