使用 `startup` 事件声明 `app` 启动前运行的函数：

```Python hl_lines="8"
{!../../docs_src/events/tutorial001.py!}
```

本例中，`startup` 事件处理器函数为项目数据库（只是**字典**）提供了一些初始值。

**FastAPI** 支持多个事件处理器函数。

只有所有 `startup` 事件处理器运行完毕，**FastAPI** 应用才开始接收请求。

## `shutdown` 事件

使用 `shutdown` 事件声明 `app` 关闭时运行的函数：

```Python hl_lines="6"
{!../../docs_src/events/tutorial002.py!}
```

此处，`shutdown` 事件处理器函数在 `log.txt` 中写入一行文本 `Application shutdown`。

```Python hl_lines="10-12"
{!../../docs_src/response_headers/tutorial001.py!}
```

/// note | "Technische Details"

Sie können auch `from starlette.responses import Response` oder `from starlette.responses import JSONResponse` verwenden.

Create a response as described in [Return a Response Directly](response-directly.md){.internal-link target=_blank} and pass the headers as an additional parameter:

```Python hl_lines="10-12"
{!../../docs_src/response_headers/tutorial001.py!}
```

/// note | "Technical Details"

You could also use `from starlette.responses import Response` or `from starlette.responses import JSONResponse`.

```

////

//// tab | Python 3.8+ non-Annotated

/// tip | "Dica"

Utilize a versão com `Annotated` se possível.

///

```Python hl_lines="8-11"
{!> ../../docs_src/dependencies/tutorial001.py!}
```

////

E pronto.

**2 linhas**.

E com a mesma forma e estrutura de todas as suas *funções de operação de rota*.

        shutil.rmtree("./templates")
    shutil.copytree("./docs_src/templates/templates/", "./templates")
    shutil.copytree("./docs_src/templates/static/", "./static")
    from docs_src.templates.tutorial001 import app

    client = TestClient(app)
    response = client.get("/items/foo")
    assert response.status_code == 200, response.text
    assert (

但 FastAPI 还可以使用数据类（<a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a>）：

```Python hl_lines="1  7-12  19-20"
{!../../docs_src/dataclasses/tutorial001.py!}
```

这还是借助于 **Pydantic** 及其<a href="https://pydantic-docs.helpmanual.io/usage/dataclasses/#use-of-stdlib-dataclasses-with-basemodel" class="external-link" target="_blank">内置的 `dataclasses`</a>。

* 一个函数 `call_next` 它将接收 `request` 作为参数.
    * 这个函数将 `request` 传递给相应的 *路径操作*.
    * 然后它将返回由相应的*路径操作*生成的 `response`.
* 然后你可以在返回 `response` 前进一步修改它.

```Python hl_lines="8-9  11  14"
{!../../docs_src/middleware/tutorial001.py!}
```

/// tip

请记住可以 <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">用'X-' 前缀</a>添加专有自定义请求头.

And then you can set the `status_code` in that *temporal* response object.

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

And then you can return any object you need, as you normally would (a `dict`, a database model, etc).

And if you declared a `response_model`, it will still be used to filter and convert the object you returned.

import pytest
from fastapi.testclient import TestClient

from ...utils import needs_pydanticv2


@pytest.fixture(name="client")
def get_client() -> TestClient:
    from docs_src.separate_openapi_schemas.tutorial001 import app

    client = TestClient(app)
    return client


def test_create_item(client: TestClient) -> None:
    response = client.post("/items/", json={"name": "Foo"})
    assert response.status_code == 200, response.text

```Python hl_lines="8"
{!../../docs_src/events/tutorial001.py!}
```

이 경우 `startup` 이벤트 핸들러 함수는 단순히 몇 가지 값으로 구성된 `dict` 형식의 "데이터베이스"를 초기화합니다.

하나 이상의 이벤트 핸들러 함수를 추가할 수도 있습니다.

그리고 응용 프로그램은 모든 `startup` 이벤트 핸들러가 완료될 때까지 요청을 받지 않습니다.

## `shutdown` 이벤트

응용 프로그램이 종료될 때 실행하려는 함수를 추가하려면 `"shutdown"` 이벤트로 선언합니다:

```Python hl_lines="6"
{!../../docs_src/events/tutorial002.py!}
```