JavaFX LoadException when passing value between controllers

Question

I tried to make multi user login form but, I have a problem with passing value from one controller to another and I dont really know what is going on.

First controller

public class Controller implements Initializable{

    public Pracownik pracownik = new Pracownik();

    @FXML
    private Label isConnected;

    @FXML
    private TextField txtUsername;

    @FXML
    private TextField txtPass;

    private Connection conn;

    // private ObservableList<Pracownik> lista = FXCollections.observableArrayList();

    public void initialize(URL url, ResourceBundle rb){
        conn = DBConnection.getConnection();

        //   lista = new Pracownik().getAll(conn);
    }

    public void login(ActionEvent event){
        try {
            if(pracownik.isLogin(conn, txtUsername.getText(), txtPass.getText()) ){

                isConnected.setText("Correct");

                if(pracownik.stanowisko(conn, txtUsername.getText(), txtPass.getText()) == 1){

                    Stage primarystage = new Stage();
                    FXMLLoader loader = new FXMLLoader();
                    Pane root = loader.load(getClass().getResource("/sample/BossView.fxml").openStream());
                    //BossController controller = (BossController) loader.getController();
                    Scene scene = new Scene(root);
                    primarystage.setScene(scene);
                    primarystage.show();
                }
                else {

                    Stage primarystage = new Stage();
                    FXMLLoader loader = new FXMLLoader();
                    Pane root = loader.load(getClass().getResource("/sample/EmployerView.fxml").openStream());
                    EmployerController controller = loader.getController();
                    controller.getUser(txtUsername.getText());


                    Scene scene = new Scene(root);
                    primarystage.setScene(scene);
                    primarystage.show();


                }
            }

            else{
                isConnected.setText("Błędne dane");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }catch (IOException e){
            e.printStackTrace();
        }

    }
}

And second controller where i want to pass txtUserName

package sample;

import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;

import java.net.URL;
import java.util.ResourceBundle;

public class EmployerController implements Initializable {


    String value;

    public void setValue(String value) {
        this.value = value;
    }

    @FXML
    private  static Label imie;

    @FXML
    private Label nazwisko;

    @FXML
    private Label mail;

    @FXML
    private Label numer;



    @Override
    public void initialize(URL url, ResourceBundle resourceBundle) {

        imie.setText(value);

    }

    public void getUser(String user){

        setValue(user);

    }

}

And this exception appears after trying to log in

javafx.fxml.LoadException: 
unknown path

I found out that

 imie.setText(value);

cause this exception. Without it, everything is fine.

Answer 1

The variable value is still null when called in the initialize Method of Employer Controller. In your example, you could just change your getUser Method like this:

public void getUser(String user){

    setValue(user);
    imie.setText(value);

}

Also, a method that is actually setting a value should not be called "get..." and it's most likely not a good idea to declare the Label static.