Kif timmaniġġja l-eċċezzjonijiet globalment b'@ControllerAdvice?

Question

IT Interview Practice · Accepted Answer

Minflok ma tgeżwer kull metodu tal-controller f'try/catch, Spring iħallik tiċċentralizza l-ġestjoni tal-errors fi klass waħda annotata `@ControllerAdvice` (jew `@RestControllerAdvice`). Il-metodi mmarkati `@ExceptionHandler` jaqbdu l-eċċezzjonijiet mitfugħa kullimkien fil-controllers tiegħek u jibdluhom f'responses HTTP konsistenti.

## Handler globali

```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);
    }
}
```

Kwalunkwe controller issa jista' sempliċement jagħmel `throw new EntityNotFoundException(...)` u jafda l-advice biex jifforma r-response.

## L-għażla moderna: ProblemDetail

Spring 6 / Boot 3 jġibu l-RFC 9457 `ProblemDetail`, body ta' error standardizzat:

```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
}
```

## Għaliex huwa importanti

Responses ta' error konsistenti u li jinqraw mill-magni huma dak li jiddistingwi API professjonali minn waħda li tikxef stack traces. L-intervistaturi jridu jaraw li tiċċentralizza l-ġestjoni (DRY), timmappja l-eċċezzjonijiet għall-istatus codes *it-tajba*, u qatt ma tesponi dettalji interni lill-klijenti. Li ssemmi `ProblemDetail` juri li int aġġornat ma' Boot 3.

Handler globali

L-għażla moderna: ProblemDetail

Għaliex huwa importanti

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