/// tip

尽可能选择使用 `Annotated` 的版本。

///

```Python hl_lines="4"
{!> ../../docs_src/body_fields/tutorial001.py!}
```

////

/// warning | "警告"

注意，与从 `fastapi` 导入 `Query`，`Path`、`Body` 不同，要直接从 `pydantic` 导入 `Field` 。

///

## 声明模型属性

然后，使用 `Field` 定义模型的属性：

//// tab | Python 3.10+

```Python hl_lines="11-14"

from dirty_equals import IsDict
from fastapi.testclient import TestClient

from docs_src.security.tutorial003_an import app

client = TestClient(app)


def test_login():
    response = client.post("/token", data={"username": "johndoe", "password": "secret"})
    assert response.status_code == 200, response.text
    assert response.json() == {"access_token": "johndoe", "token_type": "bearer"}


def test_login_incorrect_password():

import inspect

from fastapi.openapi.docs import get_redoc_html, get_swagger_ui_html


def test_strings_in_generated_swagger():
    sig = inspect.signature(get_swagger_ui_html)
    swagger_js_url = sig.parameters.get("swagger_js_url").default  # type: ignore
    swagger_css_url = sig.parameters.get("swagger_css_url").default  # type: ignore
    swagger_favicon_url = sig.parameters.get("swagger_favicon_url").default  # type: ignore

from fastapi.testclient import TestClient

from docs_src.metadata.tutorial001 import app

client = TestClient(app)


def test_items():
    response = client.get("/items/")
    assert response.status_code == 200, response.text
    assert response.json() == [{"name": "Katana"}]


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == {

from fastapi import Header, HTTPException


async def get_token_header(x_token: str = Header()):
    if x_token != "fake-super-secret-token":
        raise HTTPException(status_code=400, detail="X-Token header invalid")


async def get_query_token(token: str):
    if token != "jessica":

import os
from pathlib import Path

import pytest
from fastapi.testclient import TestClient


@pytest.fixture(scope="module")
def client():
    static_dir: Path = Path(os.getcwd()) / "static"
    print(static_dir)
    static_dir.mkdir(exist_ok=True)
    from docs_src.custom_docs_ui.tutorial001 import app

    with TestClient(app) as client:
        yield client
    static_dir.rmdir()

然后你可以在这个*临时*响应对象中设置`status_code`。

```Python hl_lines="1  9  12"
{!../../docs_src/response_change_status_code/tutorial001.py!}
```

然后你可以像平常一样返回任何你需要的对象（例如一个`dict`或者一个数据库模型）。如果你声明了一个`response_model`，它仍然会被用来过滤和转换你返回的对象。

**FastAPI**将使用这个临时响应来提取状态码（也包括cookies和头部），并将它们放入包含你返回的值的最终响应中，该响应由任何`response_model`过滤。

from fastapi import APIRouter

router = APIRouter()


@router.get("/users/", tags=["users"])
async def read_users():
    return [{"username": "Rick"}, {"username": "Morty"}]


@router.get("/users/me", tags=["users"])
async def read_user_me():
    return {"username": "fakecurrentuser"}


@router.get("/users/{username}", tags=["users"])
async def read_user(username: str):

from fastapi.testclient import TestClient

from docs_src.response_headers.tutorial002 import app

client = TestClient(app)


def test_path_operation():
    response = client.get("/headers-and-object/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "Hello World"}

# Middleware

You can add middleware to **FastAPI** applications.

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.