# 中间件

你可以向 **FastAPI** 应用添加中间件.

"中间件"是一个函数,它在每个**请求**被特定的*路径操作*处理之前,以及在每个**响应**返回之前工作.

* 它接收你的应用程序的每一个**请求**.
* 然后它可以对这个**请求**做一些事情或者执行任何需要的代码.
* 然后它将**请求**传递给应用程序的其他部分 (通过某种*路径操作*).
* 然后它获取应用程序生产的**响应** (通过某种*路径操作*).
* 它可以对该**响应**做些什么或者执行任何需要的代码.
* 然后它返回这个 **响应**.

/// note | 技术细节

如果你使用了 `yield` 关键字依赖, 依赖中的退出代码将在执行中间件*后*执行.

如果有任何后台任务(稍后记录), 它们将在执行中间件*后*运行.

///

## 创建中间件

import importlib

import pytest
from fastapi.testclient import TestClient

from ...utils import needs_py310


@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial002_py39"),
        pytest.param("tutorial002_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.body_multiple_params.{request.param}")

import importlib

import pytest
from dirty_equals import IsList
from fastapi.testclient import TestClient

from ...utils import needs_py310


@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial005_py39"),
        pytest.param("tutorial005_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.body_nested_models.{request.param}")

Please read the [Development - Contributing](https://fastapi.tiangolo.com/contributing/) guidelines in the documentation site....

from fastapi import APIRouter

router = APIRouter()


@router.post("/")
async def update_admin():

# デプロイ

**FastAPI** 製のアプリケーションは比較的容易にデプロイできます。

ユースケースや使用しているツールによっていくつかの方法に分かれます。

from typing import Annotated, Optional

import pytest
from fastapi import FastAPI, Query
from fastapi.testclient import TestClient
from pydantic import BaseModel, Field

app = FastAPI()

# =====================================================================================
# Without aliases


@app.get("/optional-str")
async def read_optional_str(p: Optional[str] = None):
    return {"p": p}

```console
// Não execute isso agora, é apenas um exemplo 🤓
$ pip install "fastapi[standard]"
---> 100%
```

</div>

Isso fará o download de um arquivo compactado com o código FastAPI, normalmente do <a href="https://pypi.org/project/fastapi/" class="external-link" target="_blank">PyPI</a>.

Ele também fará o **download** de arquivos para outros pacotes dos quais o FastAPI depende.

```console
// No ejecutes esto ahora, solo es un ejemplo 🤓
$ pip install "fastapi[standard]"
---> 100%
```

</div>

Eso descargará un archivo comprimido con el código de FastAPI, normalmente desde <a href="https://pypi.org/project/fastapi/" class="external-link" target="_blank">PyPI</a>.

También **descargará** archivos para otros paquetes de los que depende FastAPI.

import importlib

from fastapi.testclient import TestClient


def get_client() -> TestClient:
    from docs_src.conditional_openapi import tutorial001_py39

    importlib.reload(tutorial001_py39)

    client = TestClient(tutorial001_py39.app)
    return client


def test_disable_openapi(monkeypatch):
    monkeypatch.setenv("OPENAPI_URL", "")
    # Load the client after setting the env var
    client = get_client()