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- Java MySQL Select Query
- public class Connector {
- Connection con;
- PreparedStatement stmt;
- ResultSet rs;
- Connector()
- {
- try{
- Class.forName("com.mysql.jdbc.Driver");
- con=DriverManager.getConnection("jdbc:mysql://localhost/luxmidatabase","root","");
- stmt=con.prepareStatement("select * from login where username=? and password=?");
- }
- catch (Exception e)
- {
- System.out.println(e);
- }
- }
- }
- public class AttendanceHistory extends Connector
- {
- public AttendanceHistory() {
- initialize();
- }
- public JFrame frmAttendanceHistory;
- Connector con;
- private JTextField textField;
- // initialise the frame
- private void initialize() {
- frmAttendanceHistory = new JFrame();
- frmAttendanceHistory.setTitle("LEC AdminPro: Attendance History");
- frmAttendanceHistory.setBounds(100, 100, 323, 149);
- frmAttendanceHistory.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
- frmAttendanceHistory.setLocationRelativeTo(null);
- // Initialising a Grey Border, which I am going to be using later to add borders to JLabels.
- Border border = LineBorder.createGrayLineBorder();
- frmAttendanceHistory.getContentPane().setLayout(null);
- con = new Connector();
- JPanel panel_1 = new JPanel();
- panel_1.setBounds(0, 0, 307, 113);
- frmAttendanceHistory.getContentPane().add(panel_1);
- panel_1.setBorder(border);
- panel_1.setLayout(null);
- JLabel lblRegister = new JLabel("View Attendance History");
- lblRegister.setFont(new Font("Tahoma", Font.BOLD, 12));
- lblRegister.setBounds(10, 11, 193, 20);
- panel_1.add(lblRegister);
- JLabel lblStudentId = new JLabel("Student ID");
- lblStudentId.setFont(new Font("Arial", Font.PLAIN, 11));
- lblStudentId.setBounds(10, 45, 69, 14);
- panel_1.add(lblStudentId);
- // Created a Cancel button along with an OptionDialog which pops up to confirm whether user wants to cancel registration or not.
- JButton btnNewButton = new JButton("Cancel");
- btnNewButton.addActionListener(new ActionListener() {
- public void actionPerformed(ActionEvent arg0) {
- Object[] options = {"Yes", "No"};
- Component form = null;
- int n = JOptionPane.showOptionDialog(form, "Would you like to cancel the progress?", "Exit Confirmation", JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options);
- if(n == JOptionPane.YES_OPTION) {
- frmAttendanceHistory.setVisible(false);
- }
- }
- });
- btnNewButton.setBounds(159, 73, 75, 23);
- panel_1.add(btnNewButton);
- JButton button = new JButton("Submit");
- button.addActionListener(new ActionListener() {
- public void actionPerformed(ActionEvent arg0) {
- //String studentID = textField.getText();
- try {
- con.stmt.executeQuery("SELECT StudentID, date FROM attendance WHERE StudentID = 21457");
- while ( rs.next() ) {
- String date = rs.getString("date");
- System.out.println(date);
- }
- JOptionPane.showMessageDialog(frmAttendanceHistory, "Attendance has been registered.");
- frmAttendanceHistory.setVisible(false);
- } catch (SQLException e) {
- //System.out.println("Record couldn't be added!");
- JOptionPane.showMessageDialog(frmAttendanceHistory, "Attendance couldn't be registered. Please try again!");
- e.printStackTrace();
- }
- }
- });
- button.setBounds(81, 73, 75, 23);
- panel_1.add(button);
- textField = new JTextField();
- textField.setBounds(81, 42, 212, 20);
- panel_1.add(textField);
- textField.setColumns(10);
- }
- public static void main(String[] args) {
- EventQueue.invokeLater(new Runnable() {
- public void run() {
- try {
- AttendanceHistory window = new AttendanceHistory();
- window.frmAttendanceHistory.setVisible(true);
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- });
- }
- // method to make this frame visible (may be used in other classes for retrieval)
- public void setVisible(boolean b) {
- frmAttendanceHistory.setVisible(true);
- }
- }
- Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
- at AttendanceHistory$2.actionPerformed(AttendanceHistory.java:85)
- at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
- at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
- at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
- at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
- at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
- at java.awt.Component.processMouseEvent(Unknown Source)
- at javax.swing.JComponent.processMouseEvent(Unknown Source)
- at java.awt.Component.processEvent(Unknown Source)
- at java.awt.Container.processEvent(Unknown Source)
- at java.awt.Component.dispatchEventImpl(Unknown Source)
- at java.awt.Container.dispatchEventImpl(Unknown Source)
- at java.awt.Component.dispatchEvent(Unknown Source)
- at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
- at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
- at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
- at java.awt.Container.dispatchEventImpl(Unknown Source)
- at java.awt.Window.dispatchEventImpl(Unknown Source)
- at java.awt.Component.dispatchEvent(Unknown Source)
- at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
- at java.awt.EventQueue.access$000(Unknown Source)
- at java.awt.EventQueue$1.run(Unknown Source)
- at java.awt.EventQueue$1.run(Unknown Source)
- at java.security.AccessController.doPrivileged(Native Method)
- at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
- at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
- at java.awt.EventQueue$2.run(Unknown Source)
- at java.awt.EventQueue$2.run(Unknown Source)
- at java.security.AccessController.doPrivileged(Native Method)
- at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
- at java.awt.EventQueue.dispatchEvent(Unknown Source)
- at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
- at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
- at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
- at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
- at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
- at java.awt.EventDispatchThread.run(Unknown Source)
- while ( rs.next() ) {
- ResultSet rs = con.stmt.executeQuery(...);
- Statement st = con.con.createStatement();
- ResultSet rs = st.executeQuery("SELECT StudentID, date from ...");
- while (rs.hasNext()) {
- // ...
- }
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