///

## Override the default exception handlers { #override-the-default-exception-handlers }

**FastAPI** has some default exception handlers.

These handlers are in charge of returning the default JSON responses when you `raise` an `HTTPException` and when the request has invalid data.

You can override these exception handlers with your own.

{* ../../docs_src/events/tutorial001_py39.py hl[8] *}

In this case, the `startup` event handler function will initialize the items "database" (just a `dict`) with some values.

You can add more than one event handler function.

And your application won't start receiving requests until all the `startup` event handlers have completed.

### `shutdown` event { #shutdown-event }

{* ../../docs_src/handling_errors/tutorial002_py39.py hl[14] *}

## Установка пользовательских обработчиков исключений { #install-custom-exception-handlers }

Вы можете добавить пользовательские обработчики исключений с помощью <a href="https://www.starlette.dev/exceptions/" class="external-link" target="_blank">тех же утилит обработки исключений из Starlette</a>.

///

## Die Default-Exceptionhandler überschreiben { #override-the-default-exception-handlers }

**FastAPI** hat einige Default-Exceptionhandler.

Diese Handler sind dafür verantwortlich, die Default-JSON-Responses zurückzugeben, wenn Sie eine `HTTPException` `raise`n und wenn der Request ungültige Daten enthält.

{* ../../docs_src/handling_errors/tutorial002_py39.py hl[14] *}

## Instale manipuladores de exceções customizados { #install-custom-exception-handlers }

Você pode adicionar manipuladores de exceção customizados com <a href="https://www.starlette.dev/exceptions/" class="external-link" target="_blank">a mesma seção de utilidade de exceções presentes no Starlette</a>.

{* ../../docs_src/handling_errors/tutorial002_py39.py hl[14] *}

## Instalar manejadores de excepciones personalizados { #install-custom-exception-handlers }

Puedes agregar manejadores de excepciones personalizados con <a href="https://www.starlette.dev/exceptions/" class="external-link" target="_blank">las mismas utilidades de excepciones de Starlette</a>.

        }
    }

    /**
     * Loads protocol handlers from the specified base package by scanning for
     * Handler classes in subpackages and registering them as web or file protocols
     * based on their PROTOCOL_TYPE field.
     *
     * @param basePackage the base package to scan for protocol handlers
     */
    protected void loadProtocols(final String basePackage) {

new_app = UnicornMiddleware(app, some_config="rainbow")
```

But FastAPI (actually Starlette) provides a simpler way to do it that makes sure that the internal middlewares handle server errors and custom exception handlers work properly.

For that, you use `app.add_middleware()` (as in the example for CORS).

```Python
from fastapi import FastAPI
from unicorn import UnicornMiddleware

app = FastAPI()

    sub_router_shutdown: bool = False


@pytest.fixture
def state() -> State:
    return State()


@pytest.mark.filterwarnings(
    r"ignore:\s*on_event is deprecated, use lifespan event handlers instead.*:DeprecationWarning"
)
def test_router_events(state: State) -> None:
    app = FastAPI()

    @app.get("/")
    def main() -> dict[str, str]:
        return {"message": "Hello World"}

До FastAPI 0.106.0 вызывать исключения после `yield` было невозможно: код после `yield` в зависимостях выполнялся уже после отправки ответа, поэтому [Обработчики исключений](../tutorial/handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank} к тому моменту уже отработали.