Piye cara nangani kesalahan lan ngangkat pengecualian HTTP?

Question

Accepted Answer

FastAPI nangani kesalahan kanthi **ngangkat pengecualian** sing diubahaké dadi tanggapan HTTP sing bener. `HTTPException` nutupi sawetara kasuse; panganan pengecualian khusus ngidini sampeyan ngontrol format kesalahan sacara global.

## Ngangkat HTTPException

```python
from fastapi import HTTPException

@app.get("/items/{id}")
def get_item(id: int):
    item = db.get(id)
    if not item:
        raise HTTPException(status_code=404, detail="Item not found")   # → 404 JSON response
    if not item.is_public:
        raise HTTPException(status_code=403, detail="Forbidden")
    return item
```

`raise HTTPException(status_code=..., detail=...)` minangka cara idiomatik kanggo bali kesalahan — FastAPI ngasilake tanggapan JSON `{"detail": "..."}` karo status sing diwenehake. `detail` bisa apa wae nilai sing bisa diserialisaké JSON (string, dict, list).

## Kesalahan validasi otomatis (422)

```text
When request data fails Pydantic validation, FastAPI AUTOMATICALLY returns a 422
with a structured list of exactly which fields are wrong — you write nothing.
```

## Panganan pengecualian khusus (format global)

```python
from fastapi import Request
from fastapi.responses import JSONResponse

class ItemNotFound(Exception):
    def __init__(self, item_id: int): self.item_id = item_id

@app.exception_handler(ItemNotFound)         # handle a custom exception type globally
def handle_not_found(request: Request, exc: ItemNotFound):
    return JSONResponse(status_code=404, content={"error": f"Item {exc.item_id} not found"})

@app.get("/items/{id}")
def get(id: int):
    raise ItemNotFound(id)        # raise your domain exception; the handler formats it
```

Panganan pengecualian khusus ngidini sampeyan nggoleki pengecualian dhewe (domain) menyang tanggapan, memusatake format kesalahan lan nyimpan kode penganan tetep resik.

## Ngganti panganan baku

```python
from fastapi.exceptions import RequestValidationError

@app.exception_handler(RequestValidationError)   # customize the 422 validation-error format
def validation_handler(request, exc):
    return JSONResponse(status_code=422, content={"errors": exc.errors()})
```

## Mulane Penting

Penanganan kesalahan sing bener penting kanggo mbangun API sing kaandal lan profesional, lan pendekatan FastAPI iku resik lan konsisten.

HTTPException idiomatik nggawake gampil kanggo bali tanggapan kesalahan sing bener karo kode status lan pesen sing cocok — dhasar kanggo salah siji endpoint sing bisa gagal (ora ketemu, larangan, kondisi salah).

Sama pentinge yen **kesalahan validasi ditangani otomatis** (kegagalan Pydantic ngasilake tanggapan terstruktur 422 tanpa kode saka sampeyan), lan yen **panganan pengecualian khusus** ngidini sampeyan nggoleki pengecualian domain dhewe menyang tanggapan lan nggegasake format kesalahan konsisten saindhenging API — nambah keterpeliharaan (logika kesalahan terpusat) lan pengalaman klien (bentuk kesalahan sing bisa diprediksi).

Pamahaman `HTTPException`, kesalahan validasi otomatis, lan panganan khusus nutupi spektrum praktis penanganan kesalahan, dadi pengetahuan penting kanggo mbangun API sing kuat.