Spring Boot Global Exception Handler

import org.springframework.web.bind.annotation.*;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.http.*;
import java.time.Instant;
import java.util.*;

@RestControllerAdvice
public class GlobalExceptionHandler {

    record ErrorResponse(int status, String error, String message, Instant timestamp) {}

    @ExceptionHandler(ResourceNotFoundException.class)
    public ResponseEntity<ErrorResponse> handleNotFound(ResourceNotFoundException ex) {
        return ResponseEntity.status(404)
            .body(new ErrorResponse(404, "Not Found", ex.getMessage(), Instant.now()));
    }

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<Map<String, Object>> handleValidation(MethodArgumentNotValidException ex) {
        Map<String, String> fieldErrors = new HashMap<>();
        ex.getBindingResult().getFieldErrors().forEach(err ->
            fieldErrors.put(err.getField(), err.getDefaultMessage()));

        Map<String, Object> body = Map.of(
            "status", 400,
            "error", "Validation Failed",
            "fields", fieldErrors,
            "timestamp", Instant.now()
        );
        return ResponseEntity.badRequest().body(body);
    }

    @ExceptionHandler(IllegalArgumentException.class)
    public ResponseEntity<ErrorResponse> handleBadRequest(IllegalArgumentException ex) {
        return ResponseEntity.badRequest()
            .body(new ErrorResponse(400, "Bad Request", ex.getMessage(), Instant.now()));
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ErrorResponse> handleGeneric(Exception ex) {
        return ResponseEntity.status(500)
            .body(new ErrorResponse(500, "Internal Server Error",
                "An unexpected error occurred", Instant.now()));
    }
}

class ResourceNotFoundException extends RuntimeException {
    public ResourceNotFoundException(String resource, Object id) {
        super(resource + " not found with id: " + id);
    }
}