注意默认值依然是 `None`，所以该参数仍是可选的。

但现在把 `Query(max_length=50)` 放到 `Annotated` 里，我们就在告诉 FastAPI，这个值需要**额外校验**，最大长度为 50 个字符。😎

/// tip | 提示

这里用的是 `Query()`，因为这是一个**查询参数**。稍后我们还会看到 `Path()`、`Body()`、`Header()` 和 `Cookie()`，它们也接受与 `Query()` 相同的参数。

///

FastAPI 现在会：

- 对数据进行**校验**，确保最大长度为 50 个字符
- 当数据无效时向客户端展示**清晰的错误**
- 在 OpenAPI 模式的*路径操作*中**记录**该参数（因此会出现在**自动文档 UI** 中）

pkg net/http, const SameSiteStrictMode = 3
pkg net/http, const SameSiteStrictMode SameSite
pkg net/http, const StatusMisdirectedRequest = 421
pkg net/http, const StatusMisdirectedRequest ideal-int
pkg net/http, type Cookie struct, SameSite SameSite
pkg net/http, type SameSite int
pkg net/http, type Transport struct, MaxConnsPerHost int
pkg net/http/httptrace, type ClientTrace struct, Got1xxResponse func(int, textproto.MIMEHeader) error

      MockResponse
        .Builder()
        .addHeader("Set-Cookie: a=FIRST")
        .addHeader("Last-Modified: " + formatDate(-1, TimeUnit.HOURS))
        .addHeader("Cache-Control: max-age=0")
        .body("A")
        .build(),
    )
    server.enqueue(
      MockResponse
        .Builder()
        .addHeader("Set-Cookie: a=SECOND")
        .code(HttpURLConnection.HTTP_NOT_MODIFIED)

f422"}.fa-compress-arrows-alt:before{content:"\f78c"}.fa-concierge-bell:before{content:"\f562"}.fa-confluence:before{content:"\f78d"}.fa-connectdevelop:before{content:"\f20e"}.fa-contao:before{content:"\f26d"}.fa-cookie:before{content:"\f563"}.fa-cookie-bite:before{content:"\f564"}.fa-copy:before{content:"\f0c5"}.fa-copyright:before{content:"\f1f9"}.fa-cotton-bureau:before{content:"\f89e"}.fa-couch:before{content:"\f4b8"}.fa-cpanel:before{content:"\f388"}.fa-creative-commons:before{content:"\f25...

     * pass an expression that *might* be null. This could happen with:
     *
     * - a `getFooOrDefault(@Nullable Foo defaultValue)` method that returns
     *   `map.getOrDefault(FOO_KEY, defaultValue)`
     *
     * - a call that consults a chain of maps, as in `mapA.getOrDefault(key, mapB.getOrDefault(key,
     *   ...))`
     *

  The great question certainly was, what?  Alice looked all round
her at the flowers and the blades of grass, but she did not see
anything that looked like the right thing to eat or drink under
the circumstances.  There was a large mushroom growing near her,
about the same height as herself; and when she had looked under
it, and on both sides of it, and behind it, it occurred to her

Ben Guidarelli, Benjamin Mularczyk, Burness Duan, @c0g, Changming Sun, @chanis,
Corey Wharton, Dan J, Daniel Trebbien, Darren Garvey, David Brailovsky, David
Jones, Di Zeng, @DjangoPeng, Dr. Kashif Rasul, @drag0, Fabrizio (Misto) Milo,
FabríCio Ceschin, @fp, @Ghedeon, @guschmue, Gökçen Eraslan, Haosdent Huang,
Haroen Viaene, Harold Cooper, Henrik Holst, @hoangmit, Ivan Ukhov, Javier

// https://www.iana.org/domains/root/db/hiv.html
hiv

// hkt : PCCW-HKT DataCom Services Limited
// https://www.iana.org/domains/root/db/hkt.html
hkt

// hockey : Binky Moon, LLC
// https://www.iana.org/domains/root/db/hockey.html
hockey

// holdings : Binky Moon, LLC
// https://www.iana.org/domains/root/db/holdings.html
holdings

// holiday : Binky Moon, LLC

/// check | **FastAPI**へ与えたインスピレーション

素晴らしい性能を得るための方法を見つけた点。

Hug (HugはFalconをベースにしています) と一緒に、**FastAPI**が`response`引数を関数に持つことにインスピレーションを与えました。

**FastAPI**では任意ですが、ヘッダーやCookieやステータスコードを設定するために利用されています。

///

### [Molten](https://moltenframework.com/) { #molten }

**FastAPI**を構築する最初の段階でMoltenを発見しました。そして、それは非常に似たようなアイデアを持っています。

* Pythonの型ヒントに基づいている

     * Wildcard expressions will not filter workgroup names or server names.
     *
     * <blockquote><pre>
     * winnt> ls c?o*
     * clock.avi                  -rw--      82944 Mon Oct 14 1996 1:38 AM
     * Cookies                    drw--          0 Fri Nov 13 1998 9:42 PM
     * 2 items in 5ms
     * </pre></blockquote>
     *
     * @param wildcard a wildcard expression