如何在 FastAPI 中自定义特定路由的错误响应？

如何在 FastAPI 中自定义特定路由的错误响应

在 FastAPI 中，您可以通过重写来自定义特定路由的错误响应RequestValidationError 的异常处理程序。这里有几个选项：

选项 1（简单）

如果您不介意 Header 在 OpenAPI 文档中显示为可选，您可以使用以下代码：

from fastapi import Header, HTTPException

@app.post("/")
def some_route(some_custom_header: Optional[str] = Header(None)):
    if not some_custom_header:
        raise HTTPException(status_code=401, detail="Unauthorized")
    return {"some-custom-header": some_custom_header}

选项 2（自定义异常Handler)

要让 Header 按 OpenAPI 文档中的要求显示，您可以重写异常处理程序：

from fastapi import FastAPI, Request, Header, status
from fastapi.exceptions import RequestValidationError
from fastapi.responses import JSONResponse
from fastapi.encoders import jsonable_encoder

app = FastAPI()
routes_with_custom_exception = ["/"]

@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request: Request, exc: RequestValidationError):
    if request.url.path in routes_with_custom_exception:
        # Check for the specific Header in the errors
        for err in exc.errors():
            if err['loc'][0] == 'header' and err['loc'][1] == 'some-custom-header':
                return JSONResponse(content={'401': 'Unauthorized'}, status_code=401)
            
    return JSONResponse(
        status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
        content=jsonable_encoder({'detail': exc.errors(), 'body': exc.body}),
    )

@app.get("/")
def some_route(some_custom_header: str = Header(...)):
    return {'some-custom-header': some_custom_header}

选项 3（子应用程序）

您可以创建一个子应用程序并将其挂载到主应用程序。这将允许您仅为子应用程序中定义的路由自定义异常处理程序：

from fastapi import FastAPI, Request, Header
from fastapi.exceptions import RequestValidationError
from fastapi.responses import JSONResponse

app = FastAPI()

@app.get('/')
async def main():
    return {'message': 'Hello from main API'}
    

subapi = FastAPI()
   
@subapi.exception_handler(RequestValidationError)
async def validation_exception_handler(request: Request, exc: RequestValidationError):
    # Custom exception handling
    return JSONResponse(content={'401': 'Unauthorized'}, status_code=401)


@subapi.get('/')
async def sub_api_route(some_custom_header: str = Header(...)):
    return {'some-custom-header': some_custom_header}    


app.mount('/sub', subapi)

选项 4（自定义 APIRouter 和异常处理）

您可以使用自定义 APIRouter 类并在 try- except 内处理异常块：

from fastapi import FastAPI, APIRouter, Response, Request, Header, HTTPException
from fastapi.responses import JSONResponse
from fastapi.exceptions import RequestValidationError
from fastapi.routing import APIRoute
from typing import Callable

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

        async def custom_route_handler(request: Request) -> Response:
            try:
                return await original_route_handler(request)
            except RequestValidationError as e:
                # Custom exception handling
                raise HTTPException(status_code=401, detail='401 Unauthorized')
                            
        return custom_route_handler


app = FastAPI()
router = APIRouter(route_class=ValidationErrorHandlingRoute)


@app.get('/')
async def main():
    return {'message': 'Hello from main API'}
    

@router.get('/custom')
async def custom_route(some_custom_header: str = Header(...)):
    return {'some-custom-header': some_custom_header}


app.include_router(router)

选择最适合您要求的选项。

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