当键入One Jtextfield时，将数据从数据库提取到Jtextfield

嗨大家我有一个连接到oracle数据库的Swing应用程序，我想要它，这样一旦我在JTextField中键入一个值，JFrame上的其他JTextfields都会加载来自数据库的后续数据，但我似乎没有实现这个。 我已经尝试过以下代码，但它什么也没找到。

txtNo.addKeyListener(new KeyAdapter() { public void keyTyped(KeyEvent ke) { Connection conn = null; try{ Class.forName("oracle.jdbc.driver.OracleDriver"); conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE", "Username", "Password"); Statement st = conn.createStatement(); String load = "Select * from Store_info_table where PART_NUMBER = '" + txtNo.getText() + "'"; ResultSet rs = st.executeQuery(load); while(rs.next()){ txtName.setText(rs.getString("SPARE_DESC")); } }catch(Exception ae){ } } }); 

Answer 1

你知道你的数据库连接是否有效吗？ 例如，您可以在侦听器之外运行数据库部分吗？

如果是这样，我建议使用ActionListener或FocusListener 。 KeyListeners（虽然有时是必要的）通常很笨拙 – 通常有一种更好的方法（参见Java Swing：使用ActionMap和解释）：

 import java.awt.event.*; import javax.swing.*; public class Example extends Box{ JLabel txtName = new JLabel("Nothing Entered"); public temp(){ super(BoxLayout.Y_AXIS); // Add FocusListener to first field final JTextField txtNo = new JTextField(20); txtNo.addFocusListener(new CustomFocusListener(txtNo)); add(txtNo); // Add TextListener to first field final JTextField txtNo2 = new JTextField(20); txtNo2.addFocusListener(new CustomFocusListener(txtNo2)); add(txtNo2); // Add TextListener to first field final JTextField txtNo3 = new JTextField(20); txtNo3.addFocusListener(new CustomFocusListener(txtNo3)); add(txtNo3); add(new JButton("Do Something")); add(txtName); } public static void main(String[] args){ final JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.add(new Example()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } /** * Your custom focust listener that does all your SQL Work */ public class CustomFocusListener extends FocusAdapter{ JTextField field; public CustomFocusListener(JTextField field){ this.field = field; } @Override public void focusLost(FocusEvent e) { //Assuming your database connection works, this gives you an example to follow txtName.setText(field.getText()); /*Connection conn = null; try{ Class.forName("oracle.jdbc.driver.OracleDriver"); conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE", "Username", "Password"); Statement st = conn.createStatement(); String load = "Select * from Store_info_table where PART_NUMBER = '" + field.getText() + "'"; ResultSet rs = st.executeQuery(load); while(rs.next()){ txtName.setText(rs.getString("SPARE_DESC")); } }catch(Exception ae){ }*/ } } } 

Answer 2

• 用DocumentListener替换KeyListener
• EDT上的数据库连接是一个坏主意（太慢）。 有关更多信息，请参阅Swing指南中的并发性
• 您很容易受到SQL注入攻击
• 避免空的catch语句，或者你不知道出现了什么问题。 如果您不选择合适的error handling，请至少记录堆栈跟踪（通过打印它或使用Logger ）。

Answer 3

罗宾和尼克都是对的。

这是一个如何实现他们正在讨论的内容的例子……

 public class TestForm02 { public static void main(String[] args) { new TestForm02(); } public TestForm02() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (ClassNotFoundException ex) { } catch (InstantiationException ex) { } catch (IllegalAccessException ex) { } catch (UnsupportedLookAndFeelException ex) { } JFrame frame = new JFrame(); frame.setLayout(new BorderLayout()); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.add(new MyForm()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } protected class MyForm extends JPanel { private JTextField txtNo; private JTextField txtName; private String partToLoad; private Timer loadTimer; public MyForm() { setLayout(new GridBagLayout()); GridBagConstraints gbc = new GridBagConstraints(); gbc.gridx = 0; gbc.gridy = 0; gbc.insets = new Insets(2, 2, 2, 2); gbc.anchor = GridBagConstraints.WEST; txtName = new JTextField(12); txtNo = new JTextField(12); txtName.setEnabled(false); add(new JLabel("Parts #:"), gbc); gbc.gridx++; add(txtNo, gbc); gbc.gridy++; gbc.gridx = 0; add(new JLabel("Description:"), gbc); gbc.gridx++; add(txtName, gbc); txtNo.addFocusListener(new FocusAdapter() { @Override public void focusLost(FocusEvent e) { loadParts(); } }); txtNo.getDocument().addDocumentListener(new DocumentListener() { protected void update() { loadTimer.restart(); } @Override public void insertUpdate(DocumentEvent e) { update(); } @Override public void removeUpdate(DocumentEvent e) { update(); } @Override public void changedUpdate(DocumentEvent e) { update(); } }); loadTimer = new Timer(250, new ActionListener() { @Override public void actionPerformed(ActionEvent e) { loadParts(); } }); loadTimer.setRepeats(false); loadTimer.setCoalesce(true); } protected void loadParts() { String text = txtNo.getText(); // Don't want to trigger this twice... if (text == null ? partToLoad != null : !text.equals(partToLoad)) { partToLoad = text; txtNo.setEnabled(false); txtName.setEnabled(false); BackgroundWorker worker = new BackgroundWorker(); worker.execute(); } } protected class BackgroundWorker extends SwingWorker { @Override protected String doInBackground() throws Exception { // Do you're database load here. Rather then updating the text // field, assign it to variable and return it from here String desc = "Some description"; // load me :D // Inserted delay for simulation... Thread.sleep(2000); return desc; } @Override protected void done() { try { String value = get(); txtName.setText(value); txtName.setEnabled(true); txtNo.setEnabled(true); } catch (InterruptedException exp) { exp.printStackTrace(); // Log these some where useful } catch (ExecutionException exp) { exp.printStackTrace(); // Log these some where useful } } } } } 

Answer 4

谢谢大家的帮助。 我得到了我想要的东西使用NickL建议的FocusListener：

  txtNo.addFocusListener(new FocusAdapter() { public void focusLost(FocusEvent e) { Connection conn = null; try{ Class.forName("oracle.jdbc.driver.OracleDriver"); conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE", "Username", "Password"); Statement st = conn.createStatement(); String load = "Select * from Store_info_table where PART_NUMBER = '" + txtNo.getText().trim() + "'"; ResultSet rs = st.executeQuery(load); while(rs.next()){ txtName.setText(rs.getString("SPARE_DESC")); } }catch(Exception ae){ } } });