### Override request validation exceptions

When a request contains invalid data, **FastAPI** internally raises a `RequestValidationError`.

And it also includes a default exception handler for it.

To override it, import the `RequestValidationError` and use it with `@app.exception_handler(RequestValidationError)` to decorate the exception handler.

The exception handler will receive a `Request` and the exception.

Wenn ein Request ungültige Daten enthält, löst **FastAPI** intern einen `RequestValidationError` aus.

Und bietet auch einen Default-Exceptionhandler dafür.

Um diesen zu überschreiben, importieren Sie den `RequestValidationError` und verwenden Sie ihn in `@app.exception_handler(RequestValidationError)`, um Ihren Exceptionhandler zu dekorieren.

from fastapi.encoders import jsonable_encoder
from fastapi.exceptions import RequestValidationError, WebSocketRequestValidationError
from fastapi.utils import is_body_allowed_for_status_code
from fastapi.websockets import WebSocket
from starlette.exceptions import HTTPException
from starlette.requests import Request
from starlette.responses import JSONResponse, Response
from starlette.status import HTTP_422_UNPROCESSABLE_ENTITY, WS_1008_POLICY_VIOLATION

Когда запрос содержит недопустимые данные, **FastAPI** внутренне вызывает ошибку `RequestValidationError`.

А также включает в себя обработчик исключений по умолчанию.

Чтобы переопределить его, импортируйте `RequestValidationError` и используйте его с `@app.exception_handler(RequestValidationError)` для создания обработчика исключений.

Обработчик исключения получит объект `Request` и исключение.

from fastapi.encoders import jsonable_encoder
from fastapi.exceptions import RequestValidationError
from fastapi.responses import JSONResponse
from pydantic import BaseModel

app = FastAPI()


@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request: Request, exc: RequestValidationError):
    return JSONResponse(
        status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,

from typing import Callable, List

from fastapi import Body, FastAPI, HTTPException, Request, Response
from fastapi.exceptions import RequestValidationError
from fastapi.routing import APIRoute


class ValidationErrorLoggingRoute(APIRoute):
    def get_route_handler(self) -> Callable:
        original_route_handler = super().get_route_handler()

        async def custom_route_handler(request: Request) -> Response:
            try:

from fastapi import FastAPI, HTTPException
from fastapi.exceptions import RequestValidationError
from fastapi.responses import PlainTextResponse
from starlette.exceptions import HTTPException as StarletteHTTPException

app = FastAPI()


@app.exception_handler(StarletteHTTPException)
async def http_exception_handler(request, exc):
    return PlainTextResponse(str(exc.detail), status_code=exc.status_code)

## Sobrescreva exceções de validação da requisição

Quando a requisição contém dados inválidos, **FastAPI** internamente lança para o `RequestValidationError`.

Para sobrescrevê-lo, importe o `RequestValidationError` e use-o com o `@app.exception_handler(RequestValidationError)` para decorar o manipulador de exceções.

```Python hl_lines="2  14-16"
{!../../../docs_src/handling_errors/tutorial004.py!}
```

触发 `HTTPException` 或请求无效数据时，这些处理器返回默认的 JSON 响应结果。

不过，也可以使用自定义处理器覆盖默认异常处理器。

### 覆盖请求验证异常

请求中包含无效数据时，**FastAPI** 内部会触发 `RequestValidationError`。

该异常也内置了默认异常处理器。

覆盖默认异常处理器时需要导入 `RequestValidationError`，并用 `@app.excption_handler(RequestValidationError)` 装饰异常处理器。

这样，异常处理器就可以接收 `Request` 与异常。

```Python hl_lines="2  14-16"
{!../../../docs_src/handling_errors/tutorial004.py!}

```

import pytest
from fastapi import FastAPI, HTTPException
from fastapi.exceptions import RequestValidationError
from fastapi.testclient import TestClient
from starlette.responses import JSONResponse


def http_exception_handler(request, exception):
    return JSONResponse({"exception": "http-exception"})


def request_validation_exception_handler(request, exception):
    return JSONResponse({"exception": "request-validation"})