Managing Exception Handling

@RestControllerAdvice
public class GlobalExceptionHandler {
  @ExceptionHandler(EntityNotFoundException.class)
  public ResponseEntity<ProblemDetail> notFound(EntityNotFoundException ex) {
    var pd = ProblemDetail.forStatusAndDetail(HttpStatus.NOT_FOUND, ex.getMessage());
    pd.setTitle("Resource not found");
    return ResponseEntity.status(HttpStatus.NOT_FOUND).body(pd);
  }
}

public record ApiError(int status, String code, String message,
                       Instant timestamp, String path) {}

@ExceptionHandler(BusinessException.class)
ResponseEntity<ApiError> handle(BusinessException ex, HttpServletRequest req) {
  var body = new ApiError(400, ex.getCode(), ex.getMessage(),
                          Instant.now(), req.getRequestURI());
  return ResponseEntity.badRequest().body(body);
}

@ExceptionHandler(MethodArgumentNotValidException.class)
public ResponseEntity<Map<String,Object>> onValidation(MethodArgumentNotValidException ex) {
  Map<String,String> fields = ex.getBindingResult().getFieldErrors().stream()
    .collect(Collectors.toMap(FieldError::getField, FieldError::getDefaultMessage,
                              (a,b) -> a));
  return ResponseEntity.badRequest()
    .body(Map.of("status", 400, "errors", fields));
}

@Component
public class TraceErrorAttributes extends DefaultErrorAttributes {
  @Override public Map<String,Object> getErrorAttributes(WebRequest req, ErrorAttributeOptions opts) {
    Map<String,Object> attrs = super.getErrorAttributes(req, opts);
    attrs.put("traceId", MDC.get("traceId"));
    return attrs;
  }
}

@ExceptionHandler(Exception.class)
ResponseEntity<ProblemDetail> unhandled(Exception ex, HttpServletRequest req) {
  String tid = MDC.get("traceId");
  log.error("Unhandled error tid={} path={} ", tid, req.getRequestURI(), ex);
  return ResponseEntity.internalServerError()
    .body(ProblemDetail.forStatusAndDetail(HttpStatus.INTERNAL_SERVER_ERROR, "tid=" + tid));
}

@ExceptionHandler(OrderNotFoundException.class)
ProblemDetail handle(OrderNotFoundException ex) {
  ProblemDetail pd = ProblemDetail.forStatusAndDetail(HttpStatus.NOT_FOUND, ex.getMessage());
  pd.setType(URI.create("https://errors.example.com/orders/not-found"));
  pd.setTitle("Order Not Found");
  pd.setProperty("orderId", ex.getId());
  return pd;
}