How to replace 422 standard exception with custom exception only for one route in FastAPI?
I don't want to replace for the application project, just for one route. I read many docs, and I don't understand how to do this.
Example of route that I need to change the 422 exception:
from fastapi import APIRouter
from pydantic import BaseModel
router = APIRouter()
class PayloadSchema(BaseModel):
value_int: int
value_str: str
@router.post('/custom')
async def custom_route(payload: PayloadSchema):
return payload
You can register multiple error handlers with the router. You can re-declare the default handler, and then optionally call it depending on the path:
class PayloadSchema(BaseModel):
value_int: int
value_str: str
router = APIRouter()
@router.post('/standard')
async def standard_route(payload: PayloadSchema):
return payload
@app.exception_handler(RequestValidationError)
async def standard_validation_exception_handler(request: Request, exc: RequestValidationError):
return JSONResponse(
status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
content=jsonable_encoder({"detail": exc.errors(), "body": exc.body}),
)
@router.post('/custom')
async def custom_route(payload: PayloadSchema):
return payload
@app.exception_handler(RequestValidationError)
async def custom_exception_handler(request: Request, exc: RequestValidationError):
if (request.url.path == '/custom'):
return JSONResponse({"error": "Bad request, must be a valid PayloadSchema format"}, status_code=400)
else:
return await standard_validation_exception_handler(request, exc)
app = FastAPI()
app.include_router(router)
app.add_exception_handler(RequestValidationError, custom_exception_handler)
Or you can do it directly with the @app.exception_handler decorator without the router (see FastAPI docs).