🧩🚨 Spring Boot API error handling with ProblemDetail (RFC 9457)

@RestControllerAdvice
class ApiErrors {
 @ExceptionHandler(CustomerNotFoundException.class)
 ProblemDetail handle(CustomerNotFoundException ex) {
 ProblemDetail pd = ProblemDetail.forStatusAndDetail(HttpStatus.NOT_FOUND, ex.getMessage());
 pd.setTitle("Customer not found");
 pd.setType(URI.create("https://lnkd.in/evfJ_kGK"));
 pd.setProperty("customerId", ex.customerId()); // 👈 custom field
 pd.setProperty("traceId", TraceId.current()); // 👈 correlation id (example)
 return pd;
 }
}

@RestControllerAdvice
class ValidationErrors {
 record FieldIssue(String field, String message) {}

 @ExceptionHandler(MethodArgumentNotValidException.class)
 ProblemDetail handle(MethodArgumentNotValidException ex) {
 ProblemDetail pd = ProblemDetail.forStatus(HttpStatus.BAD_REQUEST);
 pd.setTitle("Validation failed");
 pd.setType(URI.create("https://lnkd.in/ehDs73e5"));
 List<FieldIssue> issues = ex.getBindingResult().getFieldErrors().stream()
 .map(fe -> new FieldIssue(fe.getField(), msg(fe)))
 .toList();
 pd.setProperty("errors", issues);
 return pd;
 }
 private String msg(FieldError fe) {
 return fe.getDefaultMessage() != null ? fe.getDefaultMessage() : "Invalid value";
 }
}