Kepiye carane nangani exception sacara global nganggo @ControllerAdvice?

Question

IT Interview Practice · Accepted Answer

Tinimbang mbungkus saben metode controller ing try/catch, Spring ngidini kowe misahake panganganan error ing siji kelas sing dianotasi `@ControllerAdvice` (utawa `@RestControllerAdvice`). Metode sing ditandhani `@ExceptionHandler` nyekel exception sing dibuwang ing endi wae ing controller-mu lan ngowahi dadi respons HTTP sing konsisten.

## Sawijining handler 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);
    }
}
```

Saiki saben controller bisa mung `throw new EntityNotFoundException(...)` lan percaya menyang advice kanggo mbentuk respons.

## Opsi modern: ProblemDetail

Spring 6 / Boot 3 ngirim RFC 9457 `ProblemDetail`, badan error sing distandardisasi:

```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
}
```

## Kenapa iki penting

Respons error sing konsisten lan bisa diwaca mesin iku sing mbedakake API profesional karo sing mbocorake stack trace. Pewawancara pengin ndeleng yen kowe misahake panganganan (DRY), memetakan exception menyang kode status sing *bener*, lan ora tau ngetokake rincian internal menyang klien. Nyebut `ProblemDetail` nuduhake yen kowe up-to-date karo Boot 3.

Sawijining handler global

Opsi modern: ProblemDetail

Kenapa iki penting

Pitakon sing gegandhengan