🪓 Fallback Middleware

A global fallback ensures your API always returns a predictable JSON response — even when something goes wrong that you didn’t catch.

When you enable use_fallback_middleware=True, APIException adds an extra middleware layer to handle any unhandled exceptions like database crashes, coding bugs, or third-party failures.

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✅ Why use it?

• No more raw HTML 500 Internal Server Error pages.
• Logs unexpected errors automatically — you get stack traces in logs, but your client gets a safe, clear JSON.
• Keeps your API response consistent no matter what goes wrong.

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⚙️ How to enable

When you call register_exception_handlers(), just pass use_fallback_middleware=True.

from fastapi import FastAPI
from APIException import register_exception_handlers

app = FastAPI()

register_exception_handlers(
    app=app,
    use_fallback_middleware=True
)

Simple as that!

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📌 Example fallback response

Imagine your database goes down. Instead of an ugly HTML page, the fallback returns this:

{
  "data": null,
  "status": "FAIL",
  "message": "Something went wrong.",
  "error_code": "ISE-500",
  "description": "An unexpected error occurred. Please try again later."
}

So frontend team can always handle errors the same way.

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⚡ Tips

✅ By default, fallback middleware is enabled (True).

✅ You can disable it by passing use_fallback_middleware=False.

✅ Works perfectly alongside your custom APIException raises.

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📚 Next

✔️ Want to integrate this with your Swagger docs?
See 📚 Swagger Integration

✔️ Want to log exceptions in detail?
Check 🪵 Logging & Debug

✔️ New here? Start with 🧩 Response Model