만약 (나중에 문서에서 다룰) 백그라운드 작업이 있다면, 모든 미들웨어가 실행되고 *난 후에* 실행됩니다.

## 미들웨어 만들기

미들웨어를 작성하기 위해서 함수 상단에 `@app.middleware("http")` 데코레이터를 사용할 수 있습니다.

미들웨어 함수는 다음 항목들을 받습니다:

* `request`.
* `request`를 매개변수로 받는 `call_next` 함수.
    * 이 함수는 `request`를 해당하는 *경로 작업*으로 전달합니다.
    * 그런 다음, *경로 작업*에 의해 생성된 `response` 를 반환합니다.
* `response`를 반환하기 전에 추가로 `response`를 수정할 수 있습니다.

```Python hl_lines="8-9  11  14"

    price: float
    tags: List[str] = field(default_factory=list)
    description: Union[str, None] = None
    tax: Union[float, None] = None


app = FastAPI()


@app.get("/items/next", response_model=Item)
async def read_next_item():
    return {
        "name": "Island In The Moon",
        "price": 12.99,
        "description": "A place to be be playin' and havin' fun",
        "tags": ["breater"],

That way, the same route class can handle gzip compressed or uncompressed requests.

```Python hl_lines="8-15"
{!../../../docs_src/custom_request_and_route/tutorial001.py!}
```

### Create a custom `GzipRoute` class

Next, we create a custom subclass of `fastapi.routing.APIRoute` that will make use of the `GzipRequest`.

This time, it will overwrite the method `APIRoute.get_route_handler()`.

This decoupling of parts, and being a "microframework" that could be extended to cover exactly what is needed was a key feature that I wanted to keep.

Given the simplicity of Flask, it seemed like a good match for building APIs. The next thing to find was a "Django REST Framework" for Flask.

!!! check "Inspired **FastAPI** to"
    Be a micro-framework. Making it easy to mix and match the tools and parts needed.

models.Base.metadata.create_all(bind=engine)

app = FastAPI()


@app.middleware("http")
async def db_session_middleware(request: Request, call_next):
    response = Response("Internal server error", status_code=500)
    try:
        request.state.db = SessionLocal()
        response = await call_next(request)
    finally:
        request.state.db.close()
    return response


# Dependency
def get_db(request: Request):

* <a href="https://cdn.jsdelivr.net/npm/swagger-ui-dist@5.9.0/swagger-ui-bundle.js" class="external-link" target="_blank">`swagger-ui-bundle.js`</a>
* <a href="https://cdn.jsdelivr.net/npm/swagger-ui-dist@5.9.0/swagger-ui.css" class="external-link" target="_blank">`swagger-ui.css`</a>

Und **ReDoc** verwendet diese Datei:

The main [Tutorial - User Guide](../tutorial/index.md){.internal-link target=_blank} should be enough to give you a tour through all the main features of **FastAPI**.

In the next sections you will see other options, configurations, and additional features.

!!! tip
    The next sections are **not necessarily "advanced"**.

    And it's possible that for your use case, the solution is in one of them.

## Read the Tutorial first

**Swagger UI** 使用如下文件：

* <a href="https://cdn.jsdelivr.net/npm/swagger-ui-dist@3/swagger-ui-bundle.js" class="external-link" target="_blank">`swagger-ui-bundle.js`</a>
* <a href="https://cdn.jsdelivr.net/npm/swagger-ui-dist@3/swagger-ui.css" class="external-link" target="_blank">`swagger-ui.css`</a>

**ReDoc** 使用如下文件：

    assert "window.opener.swaggerUIRedirectOauth2" in response.text


def test_redoc_html(client: TestClient):
    response = client.get("/redoc")
    assert response.status_code == 200, response.text
    assert "https://unpkg.com/redoc@next/bundles/redoc.standalone.js" in response.text


def test_api(client: TestClient):
    response = client.get("/users/john")

        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/items/next": {
                "get": {
                    "summary": "Read Next Item",
                    "operationId": "read_next_item_items_next_get",
                    "responses": {
                        "200": {
                            "description": "Successful Response",