/// warning | "警告"

如果您觉得现在还用不到以下技术细节，可以先跳过下面的内容。

///

`RequestValidationError` 是 Pydantic 的 <a href="https://docs.pydantic.dev/latest/concepts/models/#error-handling" class="external-link" target="_blank">`ValidationError`</a> 的子类。

**FastAPI** 调用的就是 `RequestValidationError` 类，因此，如果在 `response_model` 中使用 Pydantic 模型，且数据有错误时，在日志中就会看到这个错误。

但客户端或用户看不到这个错误。反之，客户端接收到的是 HTTP 状态码为 `500` 的「内部服务器错误」。

* 数据校验
* 自动生成文档

## 特殊的类型和校验

除了普通的单一值类型（如 `str`、`int`、`float` 等）外，你还可以使用从 `str` 继承的更复杂的单一值类型。

要了解所有的可用选项，请查看关于 <a href="https://docs.pydantic.dev/latest/concepts/types/" class="external-link" target="_blank">来自 Pydantic 的外部类型</a> 的文档。你将在下一章节中看到一些示例。

例如，在 `Image` 模型中我们有一个 `url` 字段，我们可以把它声明为 Pydantic 的 `HttpUrl`，而不是 `str`：

//// tab | Python 3.10+

```Python hl_lines="2  8"

There is a somewhat non-obvious filter present on the page that allows you to control which type of messages are displayed.
The filter is a dropdown box that appears when you click the `Severity ⬇️ ` label in the black header bar to the immediate right of the Gradle version.

If you have a large number of messages of different types, filtering by severity to see only `Error`s can be helpful when processing the report.

	github.com/antlr4-go/antlr/v4 v4.13.0 // indirect
	github.com/asaskevich/govalidator v0.0.0-20230301143203-a9d515a09cc2 // indirect
	github.com/beorn7/perks v1.0.1 // indirect
	github.com/blang/semver/v4 v4.0.0 // indirect
	github.com/census-instrumentation/opencensus-proto v0.4.1 // indirect
	github.com/chai2010/gettext-go v1.0.2 // indirect
	github.com/containerd/stargz-snapshotter/estargz v0.15.1 // indirect

    assertFailsWith<SSLPeerUnverifiedException> {
      execute(url)
    }
  }

  /**
   * Skips coalescing when hostname verifier is overridden since the intention of the hostname
   * verification is a black box.
   */
  @Test
  fun skipsWhenHostnameVerifierUsed() {
    val verifier = HostnameVerifier { name: String?, session: SSLSession? -> true }
    client = client.newBuilder().hostnameVerifier(verifier).build()

    assertThrows(IndexOutOfBoundsException.class, () -> iia3.subArray(1, 4));
  }

  /*
   * Whenever an implementation uses `instanceof` on a parameter instance, the test has to know that
   * (so much for "black box") and try instances that both do and don't pass the check. The "don't"
   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(final Collection<T> collection) {

$carousel-control-hover-opacity;\n  }\n}\n.carousel-control-prev {\n  left: 0;\n  @if $enable-gradients {\n    background-image: linear-gradient(90deg, rgba($black, .25), rgba($black, .001));\n  }\n}\n.carousel-control-next {\n  right: 0;\n  @if $enable-gradients {\n    background-image: linear-gradient(270deg, rgba($black, .25), rgba($black, .001));\n  }\n}\n\n// Icons for within\n.carousel-control-prev-icon,\n.carousel-control-next-icon {\n  display: inline-block;\n  width: $carousel-control-icon-width;\n...

* データの検証
* 自動文書化

## 特殊な型とバリデーション

`str`や`int`、`float`のような通常の単数型の他にも、`str`を継承したより複雑な単数型を使うこともできます。

すべてのオプションをみるには、<a href="https://docs.pydantic.dev/latest/concepts/types/" class="external-link" target="_blank">Pydanticのエキゾチック な型</a>のドキュメントを確認してください。次の章でいくつかの例をみることができます。

例えば、`Image`モデルのように`url`フィールドがある場合、`str`の代わりにPydanticの`HttpUrl`を指定することができます:

```Python hl_lines="4 10"
{!../../docs_src/body_nested_models/tutorial005.py!}

    assertThrows(IndexOutOfBoundsException.class, () -> iia3.subArray(1, 4));
  }

  /*
   * Whenever an implementation uses `instanceof` on a parameter instance, the test has to know that
   * (so much for "black box") and try instances that both do and don't pass the check. The "don't"
   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(final Collection<T> collection) {

    assertThrows(IndexOutOfBoundsException.class, () -> iia3.subArray(1, 4));
  }

  /*
   * Whenever an implementation uses `instanceof` on a parameter instance, the test has to know that
   * (so much for "black box") and try instances that both do and don't pass the check. The "don't"
   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(final Collection<T> collection) {