Javafx: Populating a Combobox with Data from a Mysql Database, Stringconverter Breaking the Combobox

Question

I have a ComboBox, which I'd like to populate with data from a database. Using the following code, the data that is displayed in the ComboBox is the ID of the value, not the string value.

(Partial) Java Controller Code:

@FXML
    ComboBox studentPicker;
@Override
    public void initialize(URL url, ResourceBundle rb) {
        String dbUsername = "root";
        String dbPassword = "x";
        String dbURL = "jdbc:mysql://localhost:3306/uia";
        try {
            Connection conn = DriverManager.getConnection(dbURL, dbUsername, dbPassword);
            data = FXCollections.observableArrayList();
            // Execute query and store result in a resultset
            ResultSet rs = conn.createStatement().executeQuery("SELECT username FROM user WHERE userrole='STUDENT';");
            while (rs.next()) {
                //get string from db,whichever way 
                data.add(new User(rs.getString("username")));
            }

        } catch (SQLException ex) {
            System.err.println("Error"+ex);
        }

        studentPicker.setItems(null);
        studentPicker.setItems(data);
    }

The StringConverter I tried was picked up from How to import database data into combo box in javafx, but this caused an error with the ComboBox. See image below: Image on the left is how it is supposed to be, right image is how it is when the StringConverter is added to the code.

studentPicker.setConverter(new StringConverter<User>() {

        @Override
        public String toString(User object) {
            return object.getName();
        }

        @Override
        public User fromString(String string) {
            // TODO Auto-generated method stub
            return null;
        }
    });

What I'd like to display is the usernames collected from the Database, but ID's like "is20x.User@4b6ca8f7" is displayed instead. Any suggestion to how I can solve this problem is greatly appreciated.

Accepted Answer

Answering from my comment.

You are adding a new User("username") to your data array which is why you are getting a weird String, its the ID of that particular User.

Try instead doing data.add(new User(rs.getString("username")).getUserName());, if you User class has a getUserName() method.

This may break what you are trying to do all around though, as I assume you use data more that just here. It might be best to make another variable and store you comboBox strings in that. So something like

//Init same place data is
comboString = FXCollections.observableArrayList(); //Declared somewhere else
data.add(new User(rs.getString("username")));
comboString.add(rs.getString("username"));

Answer 2

I want to share what I did to automatically set the data from MySQL database. (that is very simple)

        // first I execute the query that select name of department one by one
        resultSet = statement.executeQuery("Select name from department");

        while (resultSet.next()) {  // loop

           // Now add the comboBox addAll statement 
            comboBox.getItems().addAll(resultSet.getString("name")); 
       }

note here the "name" field in last line, is exactly spelled same as the name of the column in MySQL table.

Javafx: Populating a Combobox with Data from a Mysql Database, Stringconverter Breaking the Combobox

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Javafx: Populating a Combobox with Data from a Mysql Database, Stringconverter Breaking the Combobox

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