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这是一个 JDBC 项目。来自 WAMP 服务器上的 mySql 数据库的数据显示在 jtable 中。现在我想要在我的 Spinnerbutton 上用户输入的 ID 并删除具有该 ID 的行。我做了一个 SQL 查询，一切正常，但是执行查询时 myjtable 上的数据不会刷新。我单击我的 JNazad 按钮（我的后退按钮），然后重新进入该窗口，以便我的 Jtable 显示刷新的数据。我想我没有在 NapraviTablicu 方法中正确实现 FireTableModel，但不知道我做错了什么：

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();
            }
        });
    }
}

首先，非常感谢您的回答！

当我使用PreparedStatement我得到这个异常：

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

..所以我必须使用经典Statement

我也尝试不JTable每次都创建，我只是在我的NapraviTablicu方法中创建模型，然后通过简单地将它添加到 table 来在我的构造函数中使用该模型Tablica，但现在表没有显示任何数据。我不知道我是否在我的代码中以正确的方式实现了你的提示......

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();
            }
        });
    }
}
4

1 回答 1

3

您需要com.mysql.jdbc.Driver用作JDBC驱动程序而不是通用驱动程序JDBC/ODBC。也没有必要打电话fireTableDataChanged，你TableModel会在后台调用它。

旁注：

  • 无需JTable每次都创建。是一个可以更新DefaultTableModel的可变的。TableModel
  • PreparedStatement被认为比安全Statement
  • JFrame如果您不添加新功能，则无需扩展。直接实例是首选。
  • 为了可维护性，请考虑将您的数据库/非 UI 代码与您的 UI 代码分开。

更新：

要创建一个PreparedStatement，使用Connection#prepareStatement而不是Connection#createStatement。

PreparedStatement Stat = con2.prepareStatement(SqlQuery);

然后在执行查询时，需要使用带有空 参数列表的execute语句 ：

int rez = stat.executeUpdate();

最好将Statement& Connection& close语句放在一个finally块中。Java 使用初始小写字母作为变量名，这将使SqlQuery sqlQuery.

于 2013-03-01T01:49:11.177 回答