Unashughulikiaje exceptions kwa ujumla (globally) kwa @ControllerAdvice?

Question

IT Interview Practice · Accepted Answer

Badala ya kufunga kila controller method kwa try/catch, Spring hukuwezesha kuweka ushughulikiaji wa makosa katikati katika class moja iliyowekewa `@ControllerAdvice` (au `@RestControllerAdvice`). Methods zilizowekewa `@ExceptionHandler` hukamata exceptions zinazotupwa mahali popote katika controllers zako na kuzigeuza kuwa HTTP responses zinazolingana.

## Handler ya kimataifa (global)

```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);
    }
}
```

Controllers yoyote sasa inaweza tu `throw new EntityNotFoundException(...)` na kuamini advice itaunda response.

## Chaguo la kisasa: ProblemDetail

Spring 6 / Boot 3 huleta RFC 9457 `ProblemDetail`, body ya kosa iliyosanifiwa:

```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
}
```

## Kwa nini ni muhimu

Responses za makosa zinazolingana na zinazosomeka na mashine ndizo zinazotofautisha API ya kitaalamu na ile inayovuja stack traces. Wahoji wanataka kuona unaweka ushughulikiaji katikati (DRY), kuunganisha exceptions na status codes *sahihi*, na kutoweka wazi kamwe undani wa ndani kwa clients. Kutaja `ProblemDetail` kunaonyesha uko na wakati wa Boot 3.

Handler ya kimataifa (global)

Chaguo la kisasa: ProblemDetail

Kwa nini ni muhimu

Maswali yanayohusiana