当我尝试将列名和行数据添加到表模型时，出现空指针异常。列名来自列表，我将它们作为数组添加到表模型中。但在那里我得到了例外：tableModel.addColumn(columnNames.toArray());
tableModel.addRow(rowData);
我的完整代码：
public class DBC extends JFrame{
static String tablo;
static JTextField tf = new JTextField(20);
static int columnCount;
static JPanel tfPanel = new JPanel();
static String[] sutunlar;
static JLabel sutunLabel;
static JPanel sutunPanel = new JPanel(new BorderLayout());
static JTable table;
static JScrollPane scrollPane;
static DefaultTableModel tableModel;
static Object[] columnNames;
public static void main(String[] args) throws Exception {
Class.forName("com.mysql.jdbc.Driver");
Connection connect = DriverManager.getConnection("jdbc:mysql://localhost:3306/project"
,"root","123456789");
final Statement statement = connect.createStatement();
JLabel tabloSec = new JLabel("Tablo Seçin:");
final JComboBox<String> tablolar = new JComboBox<String>();
final DatabaseMetaData md = connect.getMetaData();
final ResultSet rs = md.getTables(null, null, "%", null);
while (rs.next()) {
tablolar.addItem(rs.getString(3));
}
tablolar.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent arg0) {
tablo = tablolar.getSelectedItem().toString();
try {
ResultSet rs2 = statement.executeQuery("SELECT * FROM "+tablo);
ResultSetMetaData rsmd = rs2.getMetaData();
columnCount = rsmd.getColumnCount();
List<String> columnNames = new ArrayList<String>();
sutunlar = new String[columnCount];
Object rowData[][] = {{""}};
for(int i=0;i<columnCount;i++){
sutunlar[i] = rsmd.getColumnLabel(i+1);
columnNames.add(sutunlar[i]);
tableModel.addColumn(columnNames.toArray());
tableModel.addRow(rowData);
}
tableModel = new DefaultTableModel(rowData, columnNames.toArray());
table = new JTable();
table.setModel(tableModel);
table.repaint();
scrollPane = new JScrollPane(table);
sutunPanel.add(scrollPane);
sutunPanel.revalidate();
sutunPanel.repaint();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
JButton ekle = new JButton("Ekle");
ekle.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e) {
try {
switch(tablo){
case "department":
statement.executeUpdate("INSERT INTO department(Name,Location) VALUES('"+tf.getText()+"')");
case "employee":
statement.executeUpdate("INSERT INTO employee(Id,FirstName,LastName,Sex,Address,Email,Salary,BirthDate,JoinDate) VALUES('"+tf.getText()+"')");
case "engineer":
statement.executeUpdate("INSERT INTO engineer(EngineerType) VALUES('"+tf.getText()+"')");
case "manager":
statement.executeUpdate("INSERT INTO manager(Department) VALUES('"+tf.getText()+"')");
case "project":
statement.executeUpdate("INSERT INTO project(Name,Number,Value) VALUES('"+tf.getText()+"')");
case "secretary":
statement.executeUpdate("INSERT INTO secretary(TypingSpeed) VALUES('"+tf.getText()+"')");
}
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
});
JButton cik = new JButton("Çık");
cik.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
});
JPanel panel = new JPanel(new FlowLayout());
panel.add(tabloSec);
panel.add(tablolar);
panel.add(sutunPanel);
panel.revalidate();
panel.add(ekle);
panel.add(cik);
JFrame frame = new JFrame("Deneme");
frame.setSize(600,600);
frame.setLocationRelativeTo(null);
frame.add(panel);
frame.setVisible(true);
}
}