Java & Access Database

Question

我正在尝试选择记录并在 JTable 中查看它。我的记录位于计算机本地的 Ms Access 数据库中。在尝试运行程序时，我收到空点异常错误，指向我的准备语句。下面是我的代码

try {
    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
    String sourceURL =
                "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb, *.accdb)};DBQ=E:/My Documents/NetBeansProjects/VictoriaMilk/3.accdb;";
    Connection li = DriverManager.getConnection(sourceURL, "Admin", "");
    System.out.println("Connection is: "+li);
    PreparedStatement pstm = conn.prepareStatement("SELECT * FROM Milk");
    // SLNO, NAMES, QTY, RATE, Deductns, BalPaid
    ResultSet Rs = pstm.executeQuery();
    while (Rs.next()) {
        model.addRow(new Object[]{Rs.getInt(1), Rs.getString(2), Rs.getString(3), Rs.getString(4), Rs.getString(5),
        Rs.getString(6), Rs.getString(7)});
    }
} catch (ClassNotFoundException ex) {
    Logger.getLogger(ResultTable.class.getName()).log(Level.SEVERE, null, ex);
} catch (SQLException sqle) {
    System.out.println(sqle);
}

Answer 1

您正在打开一个新连接并分配给局部li变量，但片刻之后您正在尝试private static Connection con哪个是null。使用来自li变量的连接：

Connection li = DriverManager.getConnection(sourceURL, "Admin", "");
PreparedStatement pstm = li.prepareStatement("SELECT * FROM Milk");