# Exceptions – `HTTPException` und `WebSocketException`

Dies sind die <abbr title="Exception – Ausnahme, Fehler: Python-Objekt, das einen Fehler nebst Metadaten repräsentiert">Exceptions</abbr>, die Sie auslösen können, um dem Client Fehler zu berichten.

# Exceptions - `HTTPException` and `WebSocketException`

These are the exceptions that you can raise to show errors to the client.

When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

from pydantic import BaseModel, create_model
from starlette.exceptions import HTTPException as StarletteHTTPException
from starlette.exceptions import WebSocketException as StarletteWebSocketException
from typing_extensions import Annotated, Doc


class HTTPException(StarletteHTTPException):
    """
    An HTTP exception you can raise in your own code to show errors to the client.

def reset_state_and_db():
    global fake_database
    global state
    fake_database = initial_fake_database.copy()
    state = initial_state.copy()


client = TestClient(app)


def test_dependency_gets_exception():
    assert state["except"] is False
    assert state["finally"] is False
    response = client.put("/invalid-user/rick", json="Morty")
    assert response.status_code == 400, response.text

from starlette import status as status

from .applications import FastAPI as FastAPI
from .background import BackgroundTasks as BackgroundTasks
from .datastructures import UploadFile as UploadFile
from .exceptions import HTTPException as HTTPException
from .exceptions import WebSocketException as WebSocketException
from .param_functions import Body as Body
from .param_functions import Cookie as Cookie
from .param_functions import Depends as Depends

    )


def test_internal_server_error():
    from docs_src.dependencies.tutorial008d_an import app

    client = TestClient(app, raise_server_exceptions=False)
    response = client.get("/items/portal-gun")
    assert response.status_code == 500, response.text

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!}

```

请求 `/unicorns/yolo` 时，路径操作会触发 `UnicornException`。

但该异常将会被 `unicorn_exception_handler` 处理。

接收到的错误信息清晰明了，HTTP 状态码为 `418`，JSON 内容如下：

```

## ❎ 🛃 ⚠ 🐕‍🦺

👆 💪 🚮 🛃 ⚠ 🐕‍🦺 ⏮️ <a href="https://www.starlette.io/exceptions/" class="external-link" target="_blank">🎏 ⚠ 🚙 ⚪️➡️ 💃</a>.

➡️ 💬 👆 ✔️ 🛃 ⚠ `UnicornException` 👈 👆 (⚖️ 🗃 👆 ⚙️) 💪 `raise`.

&amp; 👆 💚 🍵 👉 ⚠ 🌐 ⏮️ FastAPI.

👆 💪 🚮 🛃 ⚠ 🐕‍🦺 ⏮️ `@app.exception_handler()`:

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

    )


def test_internal_server_error():
    from docs_src.dependencies.tutorial008d import app

    client = TestClient(app, raise_server_exceptions=False)
    response = client.get("/items/portal-gun")
    assert response.status_code == 500, response.text

                "alias": alias,
            }
        )
    try:
        return ModelField(**kwargs)  # type: ignore[arg-type]
    except (RuntimeError, PydanticSchemaGenerationError):
        raise fastapi.exceptions.FastAPIError(
            "Invalid args for response field! Hint: "
            f"check that {type_} is a valid Pydantic field type. "
            "If you are using a return type annotation that is not a valid Pydantic "