使用ResultSetTableModel刪除JTable所選行

Question

我使用ResultSetTableModel類將我的數據庫數據顯示爲JTable。

public class ResultSetTableModel extends AbstractTableModel { 

private Connection connection; 
private Statement statement; 
private PreparedStatement prstatement; 
private ResultSet resultSet; 
private ResultSetMetaData metaData; 
private int numberOfRows; 
private boolean connectedToDatabase = false; 

public ResultSetTableModel(String driver, String url, 
     String username, String password, String query) 
     throws SQLException, ClassNotFoundException { 

    Class.forName(driver); 

    connection = DriverManager.getConnection(url, username, password); 

    prstatement = (PreparedStatement) connection.createStatement(
      ResultSet.TYPE_SCROLL_INSENSITIVE, 
      ResultSet.CONCUR_READ_ONLY); 

    connectedToDatabase = true; 
    setQuery(query); 
} 

@Override 
public Class getColumnClass(int column) throws IllegalStateException { 
    if (!connectedToDatabase) { 
     throw new IllegalStateException("Not Connected to Database"); 
    } 

    try { 
     String className = metaData.getColumnClassName(column + 1); 

     return Class.forName(className); 
    } catch (Exception exception) { 
     exception.printStackTrace(); 
    } 

    return Object.class; 
} 

@Override 
public int getColumnCount() throws IllegalStateException { 
    if (!connectedToDatabase) { 
     throw new IllegalStateException("Not Connected to Database"); 
    } 
    try { 
     return metaData.getColumnCount(); 

    } catch (SQLException sqlException) { 
     sqlException.printStackTrace(); 
    } 
    return 0; 
} 

@Override 
public String getColumnName(int column) throws IllegalStateException { 
    if (!connectedToDatabase) { 
     throw new IllegalStateException("Not Connected to Database"); 
    } 
    try { 
     return metaData.getColumnName(column + 1); 
    } catch (SQLException sqlException) { 
     sqlException.printStackTrace(); 
    } 
    return ""; 
} 

@Override 
public int getRowCount() throws IllegalStateException { 
    if (!connectedToDatabase) { 
     throw new IllegalStateException("Not Connected to Database"); 
    } 
    return numberOfRows; 
} 

@Override 
public Object getValueAt(int row, int column) 
     throws IllegalStateException { 
    if (!connectedToDatabase) { 
     throw new IllegalStateException("Not Connected to Database"); 
    } 
    try { 
     resultSet.absolute(row + 1); 
     return resultSet.getObject(column + 1); 
    } catch (SQLException sqlException) { 
     sqlException.printStackTrace(); 
    } 

    return ""; 
} 

public void setQuery(String query) 
     throws SQLException, IllegalStateException { 
    if (!connectedToDatabase) { 
     throw new IllegalStateException("Not Connected to Database"); 
    } 
    int a = prstatement.executeUpdate(query); 
    metaData = resultSet.getMetaData(); 

    resultSet.last();     // move to last row 
    numberOfRows = resultSet.getRow(); // get row number  

    fireTableStructureChanged(); 
} 

public void disconnectFromDatabase() { 
    if (!connectedToDatabase) { 
     return; 
    } 

    try { 
     prstatement.close(); 
     connection.close(); 
    } catch (SQLException sqlException) { 
     sqlException.printStackTrace(); 
    } finally 
    { 
     connectedToDatabase = false; 
    } 
} 

public void removeRecord(int row) throws SQLException { 
    String deleteQuery = "delete from mytable where id=?"; 
    PreparedStatement pStatement = connection.prepareStatement(deleteQuery); 
    pStatement.setInt(1, row); 
    int rowsAffected = pStatement.executeUpdate(); 
} 
} 

我的第二類：

public class d7Table extends JFrame implements ActionListener { 

String dbUrl = "jdbc:mysql://localhost/mydb"; 
String dbDriver = "com.mysql.jdbc.Driver"; 
public JTable table; 
public JButton dellButton; 
ResultSetTableModel rstm; 
public int selectedRow; 

public d7Table() { 
    try { 
     rstm = new ResultSetTableModel(dbDriver, dbUrl, 
       "root", "2323", "select * from mytable"); 
     table = new JTable(rstm); 

    } catch (SQLException ex) { 
     System.out.println("Could not connect to database"); 
    } catch (ClassNotFoundException cnfe) { 
    } 

    add(new JScrollPane(table), BorderLayout.CENTER); 
    add(buttonsPanel(), BorderLayout.SOUTH); 

    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    this.setSize(800, 600); 
    this.setLocation(300, 60); 
    this.setVisible(true); 
} 

public JPanel buttonsPanel() { 
    JPanel buttonP = new JPanel(); 
    dellButton = new JButton("Delete"); 
    dellButton.addActionListener(this); 
    buttonP.add(dellButton); 
    return buttonP; 
} 

@Override 
public void actionPerformed(ActionEvent e) { 
    if(e.getSource()== dellButton){ 
     selectedRow = table.getSelectedRow(); 
     if(selectedRow>0){ 
      try{ 
       rstm.removeRecord(selectedRow); 
      } 
      catch(SQLException sqle){ 
       sqle.printStackTrace(); 
      } 
     } 
     else{ 
      System.out.println("Select a row"); 
     } 
    } 
} 

public static void main(String[] args) { 
    SwingUtilities.invokeLater(new Runnable() { 
     @Override 
     public void run() { 
      new d7Table(); 
     } 
    }); 
} 
} 

現在，我的表正確填充，但是，當選擇一行並單擊刪除，沒有任何反應！

Answer 1

錯誤非常明顯 - executeQuery不能用於數據庫寫入操作。代替使用executeUpdate。

使用PreparedStatement，而不是Statement防止SQL Injection攻擊。然後簡化removeRecord，將其所有邏輯封裝在方法中，而不是與setQuery共享。

public void removeRecord(int row) throws SQLException { 
    String deleteQuery = "delete from mytable where id=?"; 
    PreparedStatement statement = connection.prepareStatement(deleteQuery); 
    statement.setInt(1, row); 
    int rowsAffected = statement.executeUpdate(); 
} 

旁白：setQuery不是一個簡單的二傳手，重命名，比方說，updateFromDatabase