但对于某些高级应用场景，还是需要添加自定义响应头：

```Python hl_lines="14"
{!../../../docs_src/handling_errors/tutorial002.py!}

```

## 安装自定义异常处理器

添加自定义处理器，要使用 [Starlette 的异常工具](https://www.starlette.io/exceptions/)。

假设要触发的自定义异常叫作 `UnicornException`。

且需要 FastAPI 实现全局处理该异常。

此时，可以用 `@app.exception_handler()` 添加自定义异常控制器：

```Python hl_lines="5-7  13-18  24"
{!../../../docs_src/handling_errors/tutorial003.py!}

```

💭 🌐 👈 **"4️⃣0️⃣4️⃣ 🚫 🔎"** ❌ (& 🤣) ❓

## ⚙️ `HTTPException`

📨 🇺🇸🔍 📨 ⏮️ ❌ 👩‍💻 👆 ⚙️ `HTTPException`.

### 🗄 `HTTPException`

```Python hl_lines="1"
{!../../../docs_src/handling_errors/tutorial001.py!}
```

### 🤚 `HTTPException` 👆 📟

`HTTPException` 😐 🐍 ⚠ ⏮️ 🌖 📊 🔗 🔗.

↩️ ⚫️ 🐍 ⚠, 👆 🚫 `return` ⚫️, 👆 `raise` ⚫️.

**"404 Not Found"** のエラー（およびジョーク）を覚えていますか？

## `HTTPException`の使用

HTTPレスポンスをエラーでクライアントに返すには、`HTTPException`を使用します。

### `HTTPException`のインポート

```Python hl_lines="1"
{!../../../docs_src/handling_errors/tutorial001.py!}
```

### コード内での`HTTPException`の発生

`HTTPException`は通常のPythonの例外であり、APIに関連するデータを追加したものです。

Pythonの例外なので、`return`ではなく、`raise`です。

# 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.

## Use o `HTTPException`

Para retornar ao cliente *responses* HTTP com erros, use o `HTTPException`.

### Import `HTTPException`

```Python hl_lines="1"
{!../../../docs_src/handling_errors/tutorial001.py!}
```

### Lance o `HTTPException` no seu código.

`HTTPException`, ao fundo, nada mais é do que a conjunção entre uma exceção comum do Python e informações adicionais relevantes para APIs.

## Использование `HTTPException`

Для возврата клиенту HTTP-ответов с ошибками используется `HTTPException`.

### Импортируйте `HTTPException`

```Python hl_lines="1"
{!../../../docs_src/handling_errors/tutorial001.py!}
```

### Вызовите `HTTPException` в своем коде

`HTTPException` - это обычное исключение Python с дополнительными данными, актуальными для API.

## `HTTPException` verwenden

Um HTTP-Responses mit Fehlern zum Client zurückzugeben, verwenden Sie `HTTPException`.

### `HTTPException` importieren

```Python hl_lines="1"
{!../../../docs_src/handling_errors/tutorial001.py!}
```

### Eine `HTTPException` in Ihrem Code auslösen

### What is "Mounting"

"Mounting" means adding a complete "independent" application in a specific path, that then takes care of handling all the sub-paths.

This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

from dirty_equals import IsDict
from fastapi.testclient import TestClient

from docs_src.handling_errors.tutorial005 import app

client = TestClient(app)


def test_post_validation_error():
    response = client.post("/items/", json={"title": "towel", "size": "XL"})
    assert response.status_code == 422, response.text
    assert response.json() == IsDict(
        {
            "detail": [
                {

之后，所有处理逻辑都一样。

但因为改变了 `GzipRequest.body`，**FastAPI** 加载请求体时会自动解压。

## 在异常处理器中访问请求体

!!! tip "提示"

    为了解决同样的问题，在 `RequestValidationError` 的自定义处理器使用 `body`  （[处理错误](../tutorial/handling-errors.md#use-the-requestvalidationerror-body){.internal-link target=_blank}）可能会更容易。

    但本例仍然可行，而且本例展示了如何与内部组件进行交互。

同样也可以在异常处理器中访问请求体。

此时要做的只是处理 `try`/`except` 中的请求：

```Python hl_lines="13  15"