java的登录界面与 数据库中表unpw的连接方法

import javax.swing.*;import java.awt.*;import java.awt.event.*;import java.sql.*;class DLFrame extends JFrame implements ActionListener, ItemListener {// 登录界面JPanel p1 = null;JPanel p2 = null;JPanel p3 = null;JLabel userName = new JLabel("用户：");JTextField txtUser = new JTextField();JLabel password = new JLabel("密码：");JPasswordField txtPwd = new JPasswordField(6);JLabel role = new JLabel("角色：");JComboBox cbrole = new JComboBox();JButton btnLogin = new JButton("登录");JButton btncz = new JButton("重置");JButton btnCancel = new JButton("取消");JLabel imageLabel;Icon image;static int OK = 1;static int CANCEL = 0;int actionCode = 0;Connection con = null;Statement stmt = null;ResultSet rs = null;int qxian = 0;public DLFrame() {// 构造方法super("登录界面");p1 = new JPanel();p2 = new JPanel();p3 = new JPanel();cbrole.addItem("管理员");cbrole.addItem("学生");image = new ImageIcon("pi.jpg");imageLabel = new JLabel(image);p1.add(imageLabel);this.setLayout(new FlowLayout());this.setBounds(100, 100, 246, 345);p2.setLayout(new GridLayout(4, 2));p2.add(userName);p2.add(txtUser);p2.add(password);p2.add(txtPwd);p2.add(role);p2.add(cbrole);p3.add(btnLogin);p3.add(btncz);p3.add(btnCancel);this.add(p1);this.add(p2);this.add(p3);this.setResizable(false);this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);this.show();btnLogin.addActionListener(this);cbrole.addItemListener(this);btncz.addActionListener(this);btnCancel.addActionListener(this);}public void connDB() { // 连接数据库try {Class.forName("com.mysql.jdbc.Driver");} catch (ClassNotFoundException e) {e.printStackTrace();}try {con = DriverManager.getConnection("jdbc:mysql://localhost:3306/student","root", "123456");stmt = con.createStatement();} catch (SQLException e) {e.printStackTrace();}}public void closeDB() // 关闭连接{try {stmt.close();con.close();} catch (SQLException e) {e.printStackTrace();}}public void itemStateChanged(ItemEvent e) {if (e.getStateChange() == ItemEvent.SELECTED) {JComboBox jcb = (JComboBox) e.getSource();qxian = jcb.getSelectedIndex();}}public void actionPerformed(ActionEvent e) {Object source = e.getSource();String un = null;String pw = null;boolean success = false;// 用于判断是否登录成功if (source == btnLogin) {if (txtUser.getText().equals("") || txtPwd.getText().equals("")) {// 判断是否输入了用户名和密码JOptionPane.showMessageDialog(null, "登录名和密码不能为空！");} else {this.connDB();try {rs = stmt.executeQuery("select * from unpw where qx="+ qxian);while (rs.next()) {un = rs.getString("un").trim();pw = rs.getString("pw").trim();if (txtUser.getText().equals(un)) {if (txtPwd.getText().equals(pw)) {actionCode = OK;this.setVisible(false);if (qxian == 0) {new ManagerFrane();// 进入管理员界面}if (qxian == 1) {new StudentFrame();// 进入学生界面}success = true;break;} else {JOptionPane.showMessageDialog(null, "密码错误！");txtPwd.setText("");success = true;}}}if (!success) {JOptionPane.showMessageDialog(null, "登录名错误！");txtUser.setText("");txtPwd.setText("");}} catch (SQLException e1) {e1.printStackTrace();}}} else if (source == btncz) {txtUser.setText("");txtPwd.setText("");} else if (source == btnCancel) {System.exit(0);
}
}