JavaFx Project 1.1 ( LoginScreenController.java)

//LoginScreenController.java

package hotelmanagementsystem;

import com.jfoenix.controls.JFXButton;
import com.jfoenix.controls.JFXDialog;
import com.jfoenix.controls.JFXDialogLayout;
import com.jfoenix.controls.JFXTextField;
import java.io.IOException;
import java.net.URL;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.geometry.Pos;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.StackPane;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
import javafx.util.Duration;
import org.controlsfx.control.Notifications;

/**
 * FXML Controller class
 *
 * @author medam
 */
public class LoginScreenController implements Initializable {

    @FXML
    private JFXTextField username;
    @FXML
    private JFXTextField password;
    @FXML
    private StackPane stackepane;

    /**
     * Initializes the controller class.
     */
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }

@FXML
    private void loginButton(MouseEvent event) {
        //video : 19-5
        if(username.getText().toString().equals("")){

            Image image = new Image("/img/delete.png");
            Notifications notification = Notifications.create()
                    .title("Error")
                    .text("Username is empty")
                    .hideAfter(Duration.seconds(3))
                    .position(Pos.BOTTOM_LEFT)
                    .graphic(new ImageView(image));
            notification.darkStyle();
            notification.show();
        }else if(password.getText().toString().equals("")){

            Image image = new Image("/img/delete.png");
            Notifications notification = Notifications.create()
                    .title("Error")
                    .text("Password is empty")
                    .hideAfter(Duration.seconds(3))
                    .position(Pos.BOTTOM_LEFT)
                    .graphic(new ImageView(image));
            notification.darkStyle();
            notification.show();

        }else {


                    boolean isExist=false;
        String userPass="";
        String userType="";

        String sql="select * from users where username='" +username.getText().toString().trim()+ "' ";
        //Connection con = DataBase.getInstance().getConnection();
        Connection connection = DBConnection.getConnection();
        try {
            PreparedStatement ps = (PreparedStatement) connection.prepareStatement(sql);
            ResultSet rs = ps.executeQuery();

            while(rs.next()){
                isExist=true;
                userPass=rs.getString(3);
                userType=rs.getString(8);

            }

            if(isExist){
                if(password.getText().toString().trim().equals(userPass)){
                    if(userType.equals("admin")){
                        //if user admin → admin Screen
                        Stage adminScreen = new Stage();
                        Parent root=null;

                        try {
                            root= FXMLLoader.load(getClass().getResource("AdminScreen.fxml"));

                         } catch (IOException ex) { Logger.getLogger(LoginScreenController.class.getName()).log(Level.SEVERE, null, ex);}

                        Stage current = (Stage) username.getScene().getWindow();
                        Scene scene = new Scene(root,1366,730);
                        adminScreen.setScene(scene);
                        adminScreen.initStyle(StageStyle.TRANSPARENT);

                        current.hide();
                        adminScreen.show();


                    }else {     //if user normal → HomeScreen


                        Stage homeScreen = new Stage();
                        Parent root=null;
                        try {
                            root= FXMLLoader.load(getClass().getResource("HomeScreen.fxml"));
                         } catch (IOException ex) { Logger.getLogger(LoginScreenController.class.getName()).log(Level.SEVERE, null, ex);}

                        Stage current = (Stage) username.getScene().getWindow();
                        Scene scene = new Scene(root,1366,730);
                        homeScreen.setScene(scene);
                        homeScreen.initStyle(StageStyle.TRANSPARENT);
                        current.hide();
                        homeScreen.show();


                    }
                }
            }else {
                        Image image = new Image("/img/delete.png");
            Notifications notification = Notifications.create()
                    .title("Error")
                    .text("Check Your username and password again !!!")
                    .hideAfter(Duration.seconds(3))
                    .position(Pos.BOTTOM_LEFT)
                    .graphic(new ImageView(image));
            notification.darkStyle();
            notification.show();

            }

        } catch (SQLException ex) {
            Logger.getLogger(LoginScreenController.class.getName()).log(Level.SEVERE, null, ex);
        }
        }
     }

    @FXML
    private void cancelButton(MouseEvent event) {
        //vid 20 : 20-6  Enhance Login Screen Design

        JFXDialogLayout dialogLayout = new JFXDialogLayout();
        dialogLayout.setHeading(new Text("Close"));
        dialogLayout.setBody(new Text("Do you want to exit !"));
        JFXButton ok = new JFXButton("ok");
        JFXButton Cancel = new JFXButton("cancel");

        JFXDialog dialog = new JFXDialog(stackepane,dialogLayout,JFXDialog.DialogTransition.CENTER);
        ok.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {

            System.exit(0);
            }
        });


        Cancel.setOnAction(new EventHandler<ActionEvent>(){
           @Override
            public void handle(ActionEvent event) {

            dialog.close();
            }
        });

        dialogLayout.setActions(ok,Cancel);
        dialog.show();

    }
}