# Handling Errors

There are many situations in which you need to notify an error to a client that is using your API.

This client could be a browser with a frontend, a code from someone else, an IoT device, etc.

You could need to tell the client that:

* The client doesn't have enough privileges for that operation.
* The client doesn't have access to that resource.
* The item the client was trying to access doesn't exist.
* etc.

/// warning

👫 📡 ℹ 👈 👆 💪 🚶 🚥 ⚫️ 🚫 ⚠ 👆 🔜.

///

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

**FastAPI** ⚙️ ⚫️ 👈, 🚥 👆 ⚙️ Pydantic 🏷 `response_model`, &amp; 👆 💽 ✔️ ❌, 👆 🔜 👀 ❌ 👆 🕹.

/// warning | "Aviso"

Você pode pular estes detalhes técnicos caso eles não sejam importantes para você neste momento.

///

`RequestValidationError` é uma subclasse do <a href="https://docs.pydantic.dev/latest/#error-handling" class="external-link" target="_blank">`ValidationError`</a> existente no Pydantic.

**FastAPI** faz uso dele para que você veja o erro no seu log, caso você utilize um modelo de Pydantic em `response_model`, e seus dados tenham erro.

/// warning | "注意"

これらは今のあなたにとって重要でない場合は省略しても良い技術的な詳細です。

///

`RequestValidationError`はPydanticの<a href="https://docs.pydantic.dev/latest/concepts/models/#error-handling" class="external-link" target="_blank">`ValidationError`</a>のサブクラスです。

**FastAPI** は`response_model`でPydanticモデルを使用していて、データにエラーがあった場合、ログにエラーが表示されるようにこれを使用しています。

Это технические детали, которые можно пропустить, если они не важны для вас сейчас.

///

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

**FastAPI** использует его для того, чтобы, если вы используете Pydantic-модель в `response_model`, и ваши данные содержат ошибку, вы увидели ошибку в журнале.

///

`RequestValidationError` ist eine Unterklasse von Pydantics <a href="https://pydantic-docs.helpmanual.io/usage/models/#error-handling" class="external-link" target="_blank">`ValidationError`</a>.

**FastAPI** verwendet diesen, sodass Sie, wenn Sie ein Pydantic-Modell für `response_model` verwenden, und ihre Daten fehlerhaft sind, einen Fehler in ihrem Log sehen.

/// 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。

## Accessing the request body in an exception handler

/// tip

To solve this same problem, it's probably a lot easier to use the `body` in a custom handler for `RequestValidationError` ([Handling Errors](../tutorial/handling-errors.md#use-the-requestvalidationerror-body){.internal-link target=_blank}).

But this example is still valid and it shows how to interact with the internal components.

///

   * Test EqualsTester with no equals or not equals objects. This checks proper handling of null,
   * incompatible class and reflexive tests
   */
  public void testTestEqualsEmptyLists() {
    equalsTester.addEqualityGroup(reference);
    equalsTester.testEquals();
  }

  /**
   * Test EqualsTester after populating equalObjects. This checks proper handling of equality and
   * verifies hashCode for valid objects
   */

   * Test EqualsTester with no equals or not equals objects. This checks proper handling of null,
   * incompatible class and reflexive tests
   */
  public void testTestEqualsEmptyLists() {
    equalsTester.addEqualityGroup(reference);
    equalsTester.testEquals();
  }

  /**
   * Test EqualsTester after populating equalObjects. This checks proper handling of equality and
   * verifies hashCode for valid objects
   */