Question

This program is used to read data from database. In the database,there are three tables pki17, pki18, pkn18. For viewing different tables,JComboBox is used and it works by changing the TableModel of the table. Also by using tableChanged method I made table editable. When a cell value in the table is changed the corresponding value in the database has to change to.

When I use tableChanged and actionPerformed methods together, value in database doesn’t get changed when I’m editing a cell in the swing table. When I remove actionPerformed method, then I can update database by editing table cells.

I need to have both abilities, to choose a table from the database by using JComboBox and update database values by editing values in the swing table.

I think the problem exists because TableModel of the table is changed in both methods. But I don’t know how to solve it.

public class TableCombobox extends JPanel implements ActionListener, TableModelListener  {
static JTable table;
static JComboBox box;
static MyTableModel model;
static Connection con = null;
static Statement stmt = null;

public TableCombobox() throws SQLException {
    super(new BorderLayout());
    table = new JTable(new MyTableModel("pki18"));
    table.setPreferredScrollableViewportSize(new Dimension(500, 400));
    table.setFillsViewportHeight(true);
    table.getModel().addTableModelListener(this);

    JScrollPane scrollPane = new JScrollPane(table);

    JPanel menuPanel = new JPanel();
    menuPanel.setLayout(new BoxLayout(menuPanel, BoxLayout.Y_AXIS));
    menuPanel.setBorder(BorderFactory.createMatteBorder(0, 0, 0, 1,
            Color.black));

    String[] dalykas = { "Chose groop", "pki17", "pki18", "pkn18" };
    box = new JComboBox(dalykas);
    box.setMaximumSize(new Dimension(150, 25));
    box.setAlignmentX(Component.LEFT_ALIGNMENT);
    box.addActionListener(this);
    box.setSelectedIndex(2);

    menuPanel.add(box);

    JPanel cards = new JPanel(new CardLayout());
    cards.add(scrollPane, "view");
    add(menuPanel, BorderLayout.LINE_START);
    add(cards, BorderLayout.CENTER);
}
public void tableChanged(TableModelEvent e) {
    int row = e.getFirstRow();
    int col = e.getColumn();
    model = (MyTableModel) e.getSource();
    String stulpPav = model.getColumnName(col);
    Object data = model.getValueAt(row, col);
    Object studId = model.getValueAt(row, 0);
    System.out.println("tableChanded works");
    try {
        new ImportData(stulpPav, data, studId);
    } catch (ClassNotFoundException e1) {
        e1.printStackTrace();
    } catch (SQLException e1) {
        e1.printStackTrace();
    }
}

public void actionPerformed(ActionEvent event) {        
        JComboBox cb = (JComboBox) event.getSource();
        String pav = (String) cb.getSelectedItem();
        if (pav != "Chose groop") {
            try {
                model = new MyTableModel(pav);
                table.setModel(model);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

private static void GUI() throws SQLException {
    JFrame frame = new JFrame("E-gradebook");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setContentPane(new TableCombobox());
    frame.pack();
    frame.setSize(800, 400);
    frame.setVisible(true);
}

public static void main(String[] args) throws SQLException {
    try {

        Class.forName("com.mysql.jdbc.Driver");
        con = DriverManager.getConnection("jdbc:mysql://localhost/pki18",
                "root", "");
        GUI();
    } catch (SQLException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e1) {
        e1.printStackTrace();
    } finally {
        if (stmt != null)
            stmt.close();
    }
}

static Connection getConnection() {
    return con;
}
}


public class ImportData {
static Connection con = TableCombobox.getConnection();

public ImportData(String a, Object b, Object c)
        throws ClassNotFoundException, SQLException {
    Statement stmt = null;
    try {

        String stulpPav = a;
        String duom = b.toString();
        String studId = c.toString();
        System.out.println(duom);
        con.setAutoCommit(false);
        stmt = con.createStatement();
        stmt.addBatch("update pki18 set " + stulpPav + " = " + duom
                + " where studento_id = " + studId + ";");
        stmt.executeBatch();
        con.commit();
    } catch (BatchUpdateException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        if (stmt != null)
            stmt.close();
        con.setAutoCommit(true);
        System.out.println("Data was imported to database");
    }
}   
}


public class MyTableModel extends AbstractTableModel{
static int rowCount;
static Object data [][];
static String columnNames [];

public  MyTableModel(String grupName) throws SQLException{
    String query ="select Studento_id, vardas_pavarde, 1_semestras,"+
            " 2_semestras, egzaminas, bendras_balas "+
            "from pki18." + grupName;

    ResultSet rs ;
    Connection con = TableCombobox.getConnection();

    Statement stmt = null;
    stmt = con.createStatement();
    rs = stmt.executeQuery(query);

    rs.last();
    rowCount = rs.getRow();
    data = new Object[rowCount][6];
    rs = stmt.executeQuery(query);
    for (int iEil = 0; iEil < rowCount; iEil++){
        rs.next();                  
        data[iEil][0] = rs.getLong("Studento_id");
        data[iEil][1] = rs.getString("Vardas_Pavarde");
        data[iEil][2]  = rs.getByte("1_semestras");
        data[iEil][3] = rs.getByte("2_semestras");
        data[iEil][4]  = rs.getByte("Egzaminas");
        data[iEil][5] = rs.getByte("bendras_balas");                    
    }

     String[] columnName  = {"Asmens_kodas","Vardas_Pavarde","1_Semestras"
            ,"2_Semestras","Egzaminas","Bendras_Balas"};
     columnNames = columnName;
}   
public int getColumnCount(){
    return columnNames.length;
}
public int getRowCount(){
    return data.length;
}
public String getColumnName(int col){
    return columnNames[col];
}
public Object getValueAt(int row, int col){
    return data[row][col];
}
public Class getColumnClass(int col){
    return getValueAt(0, col).getClass();
}
public boolean isCellEditable(int row, int col){
    return true;
}
public void setValueAt(Object value, int row, int col){
    data[row][col] = value;
    fireTableCellUpdated(row, col);
}
}

Answer 1

In the constructor, you add the table model listener to the current model only:

table.getModel().addTableModelListener(this);

In the action event, however, you replace the table model:

model = new MyTableModel(pav);
table.setModel(model);

As a consequence, the new table model won’t have the listener, and you won’t receive notifications any more. Have the actionPerformed method add the listener as well, and your problem should be fixed.