我怎样才能实现这个代码？

Question

Hey I have a problem with my java codes. If I enter a text in my IDFiELD and then press the "Enter" And then message come out "ID wasn't recognize, Try again..." but it shows the values in my table. So how can i address that problem.

So here is my code in java eclipse:

IDField.addKeyListener(new KeyAdapter() {
        public void keyPressed(KeyEvent evnt) {
            if (evnt.getKeyCode() == KeyEvent.VK_ENTER) {
                try {
                    String query = "select * from employee where IDNo = ?";
                    PreparedStatement pst = connection.prepareStatement(query);
                    pst.setString(1, IDField.getText());
                    ResultSet rs = pst.executeQuery();
                    table.setModel(DbUtils.resultSetToTableModel(rs));

                    int count = 0;
                    while (rs.next()) {
                        count += 1;
                    }
                    if (count == 1) {
                        JOptionPane.showMessageDialog(null, "ID Verified!");

                        IDField.setText(null);
                    } else {
                        JOptionPane.showMessageDialog(null, "ID was'nt recognize, Try again...");
                    }
                    rs.close();
                    pst.close();
                } catch (Exception e) {
                    JOptionPane.showMessageDialog(null, e);
                }
            }

        }
    });

I hope you can help me. Thanks.

Answer 1

Your method table.setModel(DbUtils.resultSetToTableModel(rs)); consumes the ResultSet already, so you cannot use it again to count how many results you received.

You can:

• run the query twice (simplest to code, but least clean and efficient)
• query the table model to see if there are rows
• extract the results of the query into a datastructure and convert that to your table model and also use it to check if there were results