Question

I have a database schema = which will be shown in a JCombobox as a JTable column to select a name. But I want the ID field to insert (as a foreign key) in another table.

Usually, selecting an Item in drop down, bring the selected item to the shown area of the combo box.

What I want to do is, when select any item (string) in the combo box its corresponding integer key (can be kept in a sorted map) should be shown in the combobox placeholder area, so that when take the value of the JTable.getValueAt(row, column), I get the integer key, not the string item value.
Please help me how can I do that?

Answer 1

Since there is no automatic way to do it :(.
I am using a Map to keep my values and key.

private TreeMap <Integer, String> categoryMap = new TreeMap<Integer, String>();
private JComboBox comboCategory = new JComboBox();

Get all the categories (key, value) and populate the map and combo

private void addComboColumnData() {
        try {
            Class.forName("org.sqlite.JDBC");
            Connection conn = DriverManager.getConnection(conURL);
            Statement stat = conn.createStatement();
            ResultSet rs = stat.executeQuery("SELECT id, name FROM categories");            
            comboCategory.removeAllItems();
            comboCategory.addItem(""); // blank value.
            categoryMap.clear();
            while(rs.next()){
                String name = rs.getString("name");
                comboCategory.addItem(name);
                categoryMap.put(rs.getInt("id"), name);
            }           
            rs.close();
            conn.close();
        } catch (Exception e){
            JOptionPane.showMessageDialog(this, e.toString());
            e.printStackTrace();
        }
    }

The fourth column of my JTable should be combobox,

// set the fourth column as combo
            TableColumn categoryColumn = tableData.getColumnModel().getColumn(4);
            categoryColumn.setCellEditor(new DefaultCellEditor(comboCategory));

When editing the value in the combobox, it show the text, but for updating the value in the database table I have to get the integer key.

// show Category name in text in the category field.
                    if(columnNames[i].equalsIgnoreCase("category")){
                        Object obj = rs.getObject(i+1);
                        if(obj != null && (obj instanceof Integer) )
                            row[i] = (String) categoryMap.get((Integer) obj);
                    }   

For database update,

Object value = tableData.getModel().getValueAt(rowIndex, 4);
        int categoryID = 0;

        if(value!= null){
            if (value instanceof String && !((String)value).isEmpty()) {
                categoryID = getKeyForValue((String)value);
            } else if(value instanceof Number) {
                categoryID = (Integer) value;
            }
        }

And here is the getKeyForValue,

private int getKeyForValue(String value) {
    for (Entry<Integer, String> entry : categoryMap.entrySet()) {
         if (entry.getValue().equals(value)) {
             return entry.getKey();
         }
     }
    return 0;
}