app = FastAPI()


@app.websocket_route("/")
async def index(websocket: WebSocket):
    await websocket.accept()
    await websocket.send_text("Hello, world!")
    await websocket.close()


@router.websocket_route("/router")
async def routerindex(websocket: WebSocket):
    await websocket.accept()
    await websocket.send_text("Hello, router!")
    await websocket.close()


@prefix_router.websocket_route("/")

@app.get("/large")
async def large():
    return PlainTextResponse("x" * 4000, status_code=200)


client = TestClient(app)


def test_middleware():
    response = client.get("/large", headers={"accept-encoding": "gzip"})
    assert response.status_code == 200, response.text
    assert response.text == "x" * 4000
    assert response.headers["Content-Encoding"] == "gzip"
    assert int(response.headers["Content-Length"]) < 4000

            - cookies
            - client
            - state
            - url_for
            - client_state
            - application_state
            - receive
            - send
            - accept
            - receive_text
            - receive_bytes
            - receive_json
            - iter_text
            - iter_bytes
            - iter_json
            - send_text
            - send_bytes

async def index(websocket: WebSocket, deps: DepList):
    await websocket.accept()
    await websocket.send_text(json.dumps(deps))
    await websocket.close()


@router.websocket("/router", dependencies=[create_dependency("routerindex")])
async def routerindex(websocket: WebSocket, deps: DepList):
    await websocket.accept()
    await websocket.send_text(json.dumps(deps))
    await websocket.close()

@app.websocket("/items/{item_id}/ws")
async def websocket_endpoint(
    websocket: WebSocket,
    item_id: str,
    q: int | None = None,
    cookie_or_token: str = Depends(get_cookie_or_token),
):
    await websocket.accept()
    while True:
        data = await websocket.receive_text()
        await websocket.send_text(
            f"Session cookie or query token value is: {cookie_or_token}"
        )
        if q is not None:

* `allow_credentials` - 指示跨域请求支持 cookies。默认是 `False`。另外，允许凭证时 `allow_origins` 不能设定为 `['*']`，必须指定源。
* `expose_headers` - 指示可以被浏览器访问的响应头。默认为 `[]`。
* `max_age` - 设定浏览器缓存 CORS 响应的最长时间，单位是秒。默认为 `600`。

中间件响应两种特定类型的 HTTP 请求……

### CORS 预检请求

这是些带有 `Origin` 和 `Access-Control-Request-Method` 请求头的 `OPTIONS` 请求。

* `allow_methods` - 교차-출처 요청을 허용하는 HTTP 메소드의 리스트입니다. 기본값은 `['GET']` 입니다. `['*']` 을 사용하여 모든 표준 메소드들을 허용할 수 있습니다.
* `allow_headers` - 교차-출처를 지원하는 HTTP 요청 헤더의 리스트입니다. 기본값은 `[]` 입니다. 모든 헤더들을 허용하기 위해 `['*']` 를 사용할 수 있습니다. `Accept`, `Accept-Language`, `Content-Language` 그리고 `Content-Type` 헤더는 CORS 요청시 언제나 허용됩니다.
* `allow_credentials` - 교차-출처 요청시 쿠키 지원 여부를 설정합니다. 기본값은 `False` 입니다. 또한 해당 항목을 허용할 경우 `allow_origins` 는 `['*']` 로 설정할 수 없으며, 출처를 반드시 특정해야 합니다.

    </body>
</html>
"""


class ConnectionManager:
    def __init__(self):
        self.active_connections: List[WebSocket] = []

    async def connect(self, websocket: WebSocket):
        await websocket.accept()
        self.active_connections.append(websocket)

    def disconnect(self, websocket: WebSocket):
        self.active_connections.remove(websocket)

Wenn ein eingehender Request nicht korrekt validiert wird, wird eine „400“-Response gesendet.

## `GZipMiddleware`

Verarbeitet GZip-Responses für alle Requests, die `"gzip"` im `Accept-Encoding`-Header enthalten.

Diese Middleware verarbeitet sowohl Standard- als auch Streaming-Responses.

```Python hl_lines="2  6"
{!../../../docs_src/advanced_middleware/tutorial003.py!}
```

async def websocket_endpoint(
    *,
    websocket: WebSocket,
    item_id: str,
    q: int | None = None,
    cookie_or_token: Annotated[str, Depends(get_cookie_or_token)],
):
    await websocket.accept()
    while True:
        data = await websocket.receive_text()
        await websocket.send_text(
            f"Session cookie or query token value is: {cookie_or_token}"
        )
        if q is not None: