Yaya kake sarrafa exceptions a matakin duniya da @ControllerAdvice?

Question

IT Interview Practice · Accepted Answer

Maimakon nannaɗe kowace hanyar controller a cikin try/catch, Spring yana barin ka tara sarrafa kuskure a cikin aji guda da aka annotate `@ControllerAdvice` (ko `@RestControllerAdvice`). Hanyoyin da aka yiwa alama `@ExceptionHandler` suna kama exceptions da aka jefa a ko'ina cikin controllers ɗinka kuma suna juya su zuwa amsoshin HTTP masu daidaituwa.

## Wani global handler

```java
@RestControllerAdvice // = @ControllerAdvice + @ResponseBody
public class GlobalExceptionHandler {

// Catches this exception from ANY controller and returns 404.
    @ExceptionHandler(EntityNotFoundException.class)
    @ResponseStatus(HttpStatus.NOT_FOUND)
    public ApiError notFound(EntityNotFoundException ex) {
        return new ApiError("NOT_FOUND", ex.getMessage());
    }

// Validation failures (@Valid) throw this — turn field errors into 400.
    @ExceptionHandler(MethodArgumentNotValidException.class)
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    public ApiError invalid(MethodArgumentNotValidException ex) {
        String msg = ex.getBindingResult().getFieldErrors().stream()
            .map(e -> e.getField() + " " + e.getDefaultMessage())
            .collect(Collectors.joining(", "));
        return new ApiError("VALIDATION", msg);
    }
}
```

Kowane controller yanzu zai iya kawai `throw new EntityNotFoundException(...)` kuma ya amince da advice ta tsara amsar.

## Zaɓin zamani: ProblemDetail

Spring 6 / Boot 3 suna aikawa RFC 9457 `ProblemDetail`, jikin kuskure da aka daidaita:

```java
@ExceptionHandler(PaymentDeclinedException.class)
public ProblemDetail declined(PaymentDeclinedException ex) {
    var pd = ProblemDetail.forStatusAndDetail(HttpStatus.PAYMENT_REQUIRED, ex.getMessage());
    pd.setTitle("Payment declined");
    return pd; // serialized as application/problem+json
}
```

## Me ya sa yake da muhimmanci

Amsoshin kuskure masu daidaituwa da inji zai iya karantawa su ne abin da ya raba API na ƙwararru daga wanda ke zubar da stack traces. Masu tambayoyin hira suna son ganin cewa ka tara sarrafawa (DRY), ka tsara exceptions zuwa status codes *daidai*, kuma ba za ka taɓa bayyana bayanan ciki ga abokan ciniki ba. Ambaton `ProblemDetail` yana nuna cewa kana tare da Boot 3.

Wani global handler

Zaɓin zamani: ProblemDetail

Me ya sa yake da muhimmanci

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