CODEWITHSUNDEEP
javamysqlswingjdbcjtable
Mensur Duraković
Mensur Duraković

Reputation: 25

JTable refreshed data not displayed

This is a JDBC project. Data from a mySql database on a WAMP server is displayed in jtable. Now I want that user-entered ID on my Spinnerbutton and to delete row with that ID. I made a SQL Query and everything works, but the data on the myjtable doesn't refresh when my query is executed. I click my JNazad button (my back button), and reenter that window so that my Jtable shows refreshed data. I think I haven't implemented FireTableModel correctly in my NapraviTablicu method, but don't know what I did wrong:

public class GUIBDelete extends JFrame{

    private SpinnerModel SM;
    private JSpinner Spinner;
    private JLabel LUnos;
    private JButton BNazad, BIzvrsi;
    private String ID, SqlQuery;
    private Vector NaziviKolona = new Vector();
    private Vector Podaci = new Vector();
    private JTable Tablica=new JTable();
    private JScrollPane ScrollPane;
    private DefaultTableModel model;


    private JTable NapraviTablicu(){
        try {
            String SqlQuery = "SELECT * FROM `nfc_baza`";
            Podaci.clear();
            NaziviKolona.clear();
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            Connection con = DriverManager.getConnection("jdbc:mysql://"
                    + "localhost:3306/nfc", "root", "");

            Statement Stat = con.createStatement();
            ResultSet Rez = Stat.executeQuery(SqlQuery);
            ResultSetMetaData md = Rez.getMetaData();
            int columns = md.getColumnCount();
            for (int i = 1; i <= columns; i++) {
                NaziviKolona.addElement(md.getColumnName(i));
            }
            while (Rez.next()) {
                Vector red = new Vector(columns);
                for (int i = 1; i <= columns; i++) {
                    red.addElement(Rez.getObject(i));
                }
                Podaci.addElement(red);
            }
            Rez.close();
            Stat.close();
            con.close();
        } catch (Exception e) {
            System.out.println(e);
        }
        model = new DefaultTableModel(Podaci, NaziviKolona);
        model.fireTableDataChanged();
        JTable table = new JTable(model);

        return table;

    }

    ActionListener a1 = new ActionListener() {
        public void actionPerformed(ActionEvent a) {
            dispose();
            new GUIIzbornik();
        }
    };

    ActionListener a2 = new ActionListener() {
        public void actionPerformed(ActionEvent a) {
            ID=null;
            SqlQuery = "DELETE FROM `nfc`.`nfc_baza` WHERE `nfc_baza`.`ID` = ";
            IzvrsiQuery();
            model.fireTableDataChanged();
        }

        private void IzvrsiQuery() {
            Object sp = Spinner.getValue();
            ID = sp.toString();
            SqlQuery=SqlQuery+ID;
            try {
                Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                Connection con2 = DriverManager.getConnection(
                        "jdbc:mysql://" + "localhost:3306/nfc", "root", "");
                Statement Stat = con2.createStatement();
                int Rez = Stat.executeUpdate(SqlQuery);
                Stat.close();
                con2.close();
                JOptionPane.showMessageDialog(null, "Uspješno izvrseno!",
                        "Poruka!", JOptionPane.INFORMATION_MESSAGE);

            } catch (Exception e) {
                System.out.println(e);
            }


        }

    };


    GUIBDelete(){
        setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();

        Tablica=NapraviTablicu();
        ScrollPane = new JScrollPane(Tablica);
        c.fill = GridBagConstraints.BOTH;
        c.insets = new Insets(2, 2, 2, 2);
        c.weightx = 0.1;
        c.weighty = 0.1;
        c.gridwidth = 4;
        c.gridheight = 2;
        c.gridx = 0;
        c.gridy = 0;
        add(ScrollPane, c);


        LUnos= new JLabel("<html><br>Unesite ID elementa</br> kojeg želite obrisati:<html>");
        c.gridx = 0;
        c.gridy = 2;
        c.gridwidth = 1;
        c.gridheight = 1;
        add(LUnos, c);

        SM = new SpinnerNumberModel(1, 1, 1000, 1);
        Spinner = new JSpinner(SM);
        c.gridx = 2;
        c.gridy = 2;
        c.gridwidth = 1;
        add(Spinner, c);

        BNazad = new JButton("Nazad");
        c.gridx = 0;
        c.gridy = 3;
        c.gridwidth = 1;
        BNazad.addActionListener(a1);
        add(BNazad, c);

        BIzvrsi = new JButton("Izvrši");
        c.gridx = 3;
        c.gridy = 3;
        BIzvrsi.addActionListener(a2);
        add(BIzvrsi, c);

        setSize(400, 500);
        setTitle("Brisanje podataka");
        setVisible(true);
        setLocationRelativeTo(null);

    }


    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                GUIBDelete i = new GUIBDelete();
            }
        });
    }
}

First, thank you very much for your answer!

When I use PreparedStatement I get this exception: 

java.lang.ClassCastException: com.mysql.jdbc.StatementImpl cannot be 
  cast to java.sql.PreparedStatement

..so I must use classic Statement

Also I have tried to not create JTable every time, I just make model in my NapraviTablicu method, and later use that model in my constructor by simply adding it to table Tablica, but now the table is not showing any data. I don't know if I implemented your hints right way in my code... 

public class GUIBDelete extends JFrame{

    private SpinnerModel SM;
    private JSpinner Spinner;
    private JLabel LUnos;
    private JButton BNazad, BIzvrsi;
    private String ID, SqlQuery;
    private Vector NaziviKolona = new Vector();
    private Vector Podaci = new Vector();
    private JTable Tablica=new JTable();
    private JScrollPane ScrollPane;
    private DefaultTableModel model;


    private void NapraviTablicu(){
        try {
            String SqlQuery = "SELECT * FROM `nfc_baza`";
            Podaci.clear();
            NaziviKolona.clear();
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://"
                    + "localhost:3306/nfc", "root", "");

            Statement Stat = con.createStatement();
            ResultSet Rez = Stat.executeQuery(SqlQuery);
            ResultSetMetaData md = Rez.getMetaData();
            int columns = md.getColumnCount();
            for (int i = 1; i <= columns; i++) {
                NaziviKolona.addElement(md.getColumnName(i));
            }
            while (Rez.next()) {
                Vector red = new Vector(columns);
                for (int i = 1; i <= columns; i++) {
                    red.addElement(Rez.getObject(i));
                }
                Podaci.addElement(red);
            }
            Rez.close();
            Stat.close();
            con.close();

        } catch (Exception e) {
            System.out.println(e);
        }
        model = new DefaultTableModel(Podaci, NaziviKolona);
        //model.fireTableDataChanged();

    }

    ActionListener a1 = new ActionListener() {
        public void actionPerformed(ActionEvent a) {
            dispose();
            new GUIIzbornik();
        }
    };

    ActionListener a2 = new ActionListener() {
        public void actionPerformed(ActionEvent a) {
            ID=null;
            SqlQuery = "DELETE FROM `nfc`.`nfc_baza` WHERE `nfc_baza`.`ID` = ";
            IzvrsiQuery();
            //model.fireTableDataChanged();
        }

        private void IzvrsiQuery() {
            Object sp = Spinner.getValue();
            ID = sp.toString();
            SqlQuery=SqlQuery+ID;
            try {
                Class.forName("com.mysql.jdbc.Driver");
                Connection con2 = DriverManager.getConnection(
                        "jdbc:mysql://" + "localhost:3306/nfc", "root", "");
                PreparedStatement Stat = (PreparedStatement) con2.createStatement();
                int Rez = Stat.executeUpdate(SqlQuery);
                Stat.close();
                con2.close();
                JOptionPane.showMessageDialog(null, "Uspješno izvrseno!",
                        "Poruka!", JOptionPane.INFORMATION_MESSAGE);

            } catch (Exception e) {
                System.out.println(e);
            }


        }

    };


    GUIBDelete(){
        setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();

        Tablica=new JTable(model);
        ScrollPane = new JScrollPane(Tablica);
        c.fill = GridBagConstraints.BOTH;
        c.insets = new Insets(2, 2, 2, 2);
        c.weightx = 0.1;
        c.weighty = 0.1;
        c.gridwidth = 4;
        c.gridheight = 2;
        c.gridx = 0;
        c.gridy = 0;
        add(ScrollPane, c);


        LUnos= new JLabel("<html><br>Unesite ID elementa</br> kojeg želite obrisati:<html>");
        c.gridx = 0;
        c.gridy = 2;
        c.gridwidth = 1;
        c.gridheight = 1;
        add(LUnos, c);

        SM = new SpinnerNumberModel(1, 1, 1000, 1);
        Spinner = new JSpinner(SM);
        c.gridx = 2;
        c.gridy = 2;
        c.gridwidth = 1;
        add(Spinner, c);

        BNazad = new JButton("Nazad");
        c.gridx = 0;
        c.gridy = 3;
        c.gridwidth = 1;
        BNazad.addActionListener(a1);
        add(BNazad, c);

        BIzvrsi = new JButton("Izvrši");
        c.gridx = 3;
        c.gridy = 3;
        BIzvrsi.addActionListener(a2);
        add(BIzvrsi, c);

        setSize(400, 500);
        setTitle("Brisanje podataka");
        setVisible(true);
        setLocationRelativeTo(null);

    }


    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                GUIBDelete i = new GUIBDelete();
            }
        });
    }
}

Upvotes: 0

Views: 389

Answers (1)

Reimeus
Reimeus

Reputation: 159784

You need to use com.mysql.jdbc.Driver as your JDBC driver rather than the generic JDBC/ODBC one. Also there's no need to call fireTableDataChanged, your TableModel will call this under the hood.

Side Notes:

  • No need to create the JTable every time. DefaultTableModel is a mutable TableModel which can be updated.
  • PreparedStatement is considered safer than Statement
  • There's no need to extend JFrame if you're not adding new functionality. A direct instance is preferred.
  • For maintainability consider keeping your database/non UI code separate from your UI code.

Update:

To create a PreparedStatement, use Connection#prepareStatement rather than Connection#createStatement. 

PreparedStatement Stat = con2.prepareStatement(SqlQuery);

Then when executing the query, it is necessary to use the execute statement with the empty argument list:

int rez = stat.executeUpdate();

Also better to place Statement & Connection & close statements in a finally block. Java uses an initial lowercase letter for variables names which would make SqlQuery sqlQuery.

Upvotes: 3

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