Nexios

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Error Handling ​

Nexios provides a robust and flexible error handling system that allows you to manage exceptions gracefully and return appropriate responses to clients. This documentation covers all aspects of error handling in Nexios applications.

HTTP Exceptions ​

Nexios includes built-in HTTP exceptions for common error scenarios:

python
from nexios.exceptions import HTTPException
@app.get("/users/{user_id}")
async def get_user(request, response):
    user = await find_user(request.path_params['user_id'])
    if not user:
        raise HTTPException(detail="User not found", status = 404)
    return response.json(user)

Raising HTTP Exceptions ​

All HTTP exceptions accept these parameters:

  • status_code: HTTP status code (required for base HTTPException)

  • detail: Error message or details

  • headers: Custom headers to include in the response

python
raise HTTPException(
    status_code=400,
    detail="Invalid request parameters",
    headers={"X-Error-Code": "INVALID_PARAMS"}
)

Custom Exception Classes ​

Nexios provides a way to create custom exception classes that extend the built-in HTTPException class. This allows you to define specific error handling behavior for specific types of errors.

python
from nexios.exceptions import HTTPException

class PaymentRequiredException(HTTPException):
    def __init__(self, detail: str = None):
        super().__init__(
            status_code=402,
            detail=detail or "Payment required",
            headers={"X-Payment-Required": "true"}
        )

@app.get("/premium-content")
async def get_premium_content(request, response):
    if not request.user.has_premium:
        raise PaymentRequiredException("Upgrade to premium to access this content")
    return response.json({"message": "Premium content available"})

Exception Handlers ​

Nexios provides a way to register custom exception handlers for specific exception types or HTTP status codes. This allows you to define custom error handling behavior for specific errors.

python
from nexios.exceptions import HTTPException

async def handle_payment_required_exception(request, response, exception):
    return response.json({"error": "Payment required"}, status=402)

app.add_exception_handler(PaymentRequiredException, handle_payment_required_exception)

@app.get("/premium-content")
async def get_premium_content(request, response):
    if not request.user.has_premium:
        raise PaymentRequiredException("Upgrade to premium to access this content")
    return response.json({"message": "Premium content available"})

Status Code Handlers ​

Handle exceptions by status code:

python
from nexios.exceptions import HTTPException

async def handle_payment_required_exception(request, response, exception):
    return response.json({"error": "Payment required"}, status=402)

app.add_exception_handler(402, handle_payment_required_exception)

@app.get("/premium-content")
async def get_premium_content(request, response):
    if not request.user.has_premium:
        raise PaymentRequiredException("Upgrade to premium to access this content")
    return response.json({"message": "Premium content available"})

In the provided example, we demonstrate how to create a custom exception handler for handling specific exceptions in a Nexios application. We define a custom exception handler handle_payment_required_exception, which returns a JSON response with an error message and a status code when a PaymentRequiredException is raised. This handler is registered with the application using app.add_exception_handler(). This approach allows for granular control over error responses, improving the user experience by providing clear feedback for specific scenarios, such as when a user tries to access premium content without a subscription.

Debug Mode ​

Enable debug mode for detailed error responses:

python

from nexios import MakeConfig

config = MakeConfig({"debug": True})
app = NexiosApp(config=config)

🥹Tip

You can modify the app config simply as app.config.debug = True