Question

当我尝试将数据加载到JTable中时出现以下错误。

线程中的异常＆＃34; AWT-EventQueue-0＆＃34;显示java.lang.NullPointerException 在com.tfc.cheque.handle.dao.impl.ChequeDAOImpl.getCheques（ChequeDAOImpl.java:23）在com.tfc.cheque.handle.ui.ChequeGUI。（ChequeGUI.java:38）在TestChequeDAO $ 1.run（TestChequeDAO.java:30）在java.awt.event.InvocationEvent.dispatch（InvocationEvent.java:209） at java.awt.EventQueue.dispatchEvent（EventQueue.java:597） at java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:273） at java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java:183） at java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:173） at java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:168） at java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:160）在java.awt.EventDispatchThread.run（EventDispatchThread.java:121）

这是我的主要课程：

public class TestChequeDAO {

public static void main(String[] args) throws SQLException{
    DBConnection connection = new DBConnection();
    connection.setUser("");
    connection.setPswd("");

    ChequeDAOImpl dao = new ChequeDAOImpl();
    dao.setConnection(connection);

    List<Cheque> cheques = dao.getCheques();

    EventQueue.invokeLater(new Runnable() {

        public void run() {
            ChequeGUI cgui;
            try {
                cgui = new ChequeGUI();

                cgui.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                cgui.pack();
                cgui.setVisible(true);

            } catch (SQLException e) {

                e.printStackTrace();
            }


        }
    });


}

}

这是我的gui课程：

public class ChequeGUI extends JFrame {

JTable guiTable = new JTable();
DefaultTableModel model = new DefaultTableModel(new Object[][]{},new String[]{"Name","Amount","Date"});

public ChequeGUI() throws SQLException {

    guiTable.setModel(model);
    add(new JScrollPane(guiTable));

    //Populate Table
    ChequeDAOImpl chqdi = new ChequeDAOImpl();
    List<Cheque> cheques = chqdi.getCheques();

    for(Cheque cq : cheques){
        model.addRow(new Object[]{cq.getName(),cq.getAmount(),cq.getDate()});
    }


}

}

这是我编写查询的地方：

public class ChequeDAOImpl implements ChequeDAO{
//DB2 connection
private DBConnection dbConnection;

public List<Cheque> getCheques() throws SQLException{
    List<Cheque> cheques = new ArrayList<Cheque>();
    Connection connection = dbConnection.getConnection();
    try{
        Statement statement = connection.createStatement();
        ResultSet result = statement.executeQuery("select * from LIB.DATA");


        while(result.next()) {
            Cheque cheque = new Cheque();      
            cheque.setAmount(result.getDouble("AMOUNT"));
            cheque.setDate(result.getDate("DATE"));
            cheque.setName(result.getString("NAME"));

            cheques.add(cheque);

            for(Cheque chq : cheques){

                System.out.println("Name: " + result.getString("NAME"));
                System.out.println("Amount: " + result.getDouble("AMOUNT"));
                System.out.println("Date: " + result.getDate("DATE"));
            }               



        } 
    }catch(Exception exception){
        exception.printStackTrace();
    }finally{
        connection.close();
    }
    return cheques;
}

public DBConnection getConnection() {
    return dbConnection;
}

public void setConnection(DBConnection connection) {
    this.dbConnection = connection;
}

}

Answer 1

您需要初始化DBConnection dbConnection，这在很大程度上取决于您的应用程序的工作方式

填充JTable时出现NullPointer异常

1 个答案: