从头开始从DB加载数据

Question

有人可以帮助我在启动程序后立即从数据库加载数据，即在start方法中。我可以在点击的按钮上加载它，但在start方法中，我得到一个NullPointerException。这是代码：

public class Main extends Application {
    Controller objekt = new Controller();

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("FXML/sample.fxml"));
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(root));
        objekt.učitajRadnike();
        primaryStage.show();
    }


    public static void main(String[] args) {
        launch(args);
    }
}


public class Controller {
    @FXML
    TableView<radnici> radniciTabela;
    @FXML
    TableColumn<radnici, String> ime = new TableColumn<>();
    @FXML
    TableColumn<radnici, String> adresa = new TableColumn<>();
    @FXML
    TableColumn<radnici, String> grad = new TableColumn<>();
    @FXML
    TableColumn<radnici, String> telefon = new TableColumn<>();
    @FXML
    TableColumn<radnici, String> email = new TableColumn<>();
    @FXML
    Button učitajBtn;
    ObservableList<radnici> lista;

    public ObservableList<radnici> getData() {
        lista = FXCollections.observableArrayList();
        try {
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3307/radnici", "root", "Kvark");
            Statement stm = conn.createStatement();
            ResultSet rs = stm.executeQuery("SELECT *FROM kontaktinfo");
            while (rs.next()) {
                lista.add(
                        new radnici(rs.getString("ime"),
                                rs.getString("adresa"),
                                rs.getString("grad"),
                                rs.getString("telefon"),
                                rs.getString("email")));
            }
            System.out.println("umetanje u listu završeno");
        } catch (Exception e) {
            System.out.println("Greška je " + e);
        }
        return lista;

    }

    @FXML
    public void učitajRadnike() {
        ime.setCellValueFactory(new PropertyValueFactory<radnici, String>("ime"));
        adresa.setCellValueFactory(new PropertyValueFactory<radnici, String>("adresa"));
        grad.setCellValueFactory(new PropertyValueFactory<radnici, String>("grad"));
        telefon.setCellValueFactory(new PropertyValueFactory<radnici, String>("telefon"));
        email.setCellValueFactory(new PropertyValueFactory<radnici, String>("email"));

        radniciTabela.setItems(getData());


    }




}

这可能是微不足道的，但我真的不明白。该方法不应为null，它适用于单击按钮。顺便说一句，我正在使用SceneBuilder添加动作，并创建UI。