Populating the combobox from database - javafx

Question

I want to build a ComboBox that is populated with data from database but it's not working.The Scene Builder is fine i made the fxid:comboBoxx and onAction:fillComboBox2 and its running,but i dont have any data,just blank.I dont know where is the problem,i tried everything i know.
public class FXMLController implements Initializable {
#FXML
private ComboBox comboBoxx;
final ObservableList options = FXCollections.observableArrayList();
public void initialize(URL url, ResourceBundle rb) {
}
public void fillComboBox2() {
String connectionUrl = "jdbc:sqlserver://localhost:1433;" + "databaseName=TestDB;integratedSecurity=true;";
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection con = DriverManager.getConnection(connectionUrl);
String query = "select artikulli from product_table";
PreparedStatement statement = con.prepareStatement(query);
ResultSet set = statement.executeQuery();
while(set.next()){
options.add(set.getString("artikulli"));
}
statement .close();
set.close();
} catch(ClassNotFoundException | SQLException ex) {
Logger.getLogger(JavaFXExample.class.getName()).log(Level.SEVERE, null, ex);
}
}
}

Answer 1

There are a couple of things to address here. First of all, you are never actually telling your ComboBox where to find the data it's meant to display.
This is done using the comboBoxx.setItems() method. This is easy to do within the controller's initialize() method.
Also, you stated that you set the onAction property of the ComboBox to your fillComboBox2() method. This is not correct. Doing so will cause the fillComboBox2() method to be called every time you click on the dropdown for the ComboBox.
Instead, you should fill the ComboBox when loading the scene. So, remove the onAction definition from your FXML document.
Lastly, it would be a good idea to change that method entirely. In my updated code below, you'll see that I've changed it to a private method that returns a List<String>. We can use that List to populate the ComboBox.
Now, when the scene is being loaded, the comboBoxx.setItems() method is called, and the List<String> from the getData() method is used to populate it.
The code below also has some comments to help explain the flow.
THE CODE
import javafx.collections.FXCollections;
import javafx.fxml.FXML;
import javafx.scene.control.ComboBox;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
public class FXMLController {
// If you ComboBox is going to display Strings, you should define that datatype here
#FXML
private ComboBox<String> comboBoxx;
#FXML
private void initialize() {
// Within this initialize method, you can initialize the data for the ComboBox. I have changed the
// method from fillComboBox2() to getData(), which returns a List of Strings.
// We need to set the ComboBox to use that list.
comboBoxx.setItems(FXCollections.observableArrayList(getData()));
}
/**
* Here we will define the method that builds the List used by the ComboBox
*/
private List<String> getData() {
String connectionUrl = "jdbc:sqlserver://localhost:1433;" + "databaseName=TestDB;integratedSecurity=true;";
// Define the data you will be returning, in this case, a List of Strings for the ComboBox
List<String> options = new ArrayList<>();
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection con = DriverManager.getConnection(connectionUrl);
String query = "select artikulli from product_table";
PreparedStatement statement = con.prepareStatement(query);
ResultSet set = statement.executeQuery();
while (set.next()) {
options.add(set.getString("artikulli"));
}
statement.close();
set.close();
// Return the List
return options;
} catch (ClassNotFoundException | SQLException ex) {
Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
return null;
}
}
}