基础java项目２（ Login ）

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JButton;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JOptionPane;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.WindowEvent;
import javax.swing.JComboBox;
import java.util.*;
import javax.swing.plaf.OptionPaneUI;

class Login extends JFrame
{
JFrame loginframe = new JFrame("登陆");
JLabel jlbmanager;
JLabel jlbpassword;
JComboBox jcmbmanager;
JTextField jtfpassword;
JPanel manager_pan;
JPanel password_pan;
JPanel button_pan;
JButton jtbOK;
private String username;
DATAConnection dcon = null;
Vector managerV = null;
//初始化
public void jbinit(){
loginframe.setResizable(false);
jcmbmanager = new JComboBox(getmanager());
jcmbmanager.setEditable(false);
jlbmanager = new JLabel("管理员:");
manager_pan = new JPanel();
manager_pan.setLayout(new GridLayout(1,2));
manager_pan.add(jlbmanager);
manager_pan.add(jcmbmanager);
loginframe.getContentPane().add(manager_pan,BorderLayout.NORTH);
jlbpassword = new JLabel("密 码:");
jtfpassword = new JTextField(10);
password_pan = new JPanel();
password_pan.setLayout(new GridLayout(1,2));
password_pan.add(jlbpassword);
password_pan.add(jtfpassword);
loginframe.getContentPane().add(password_pan, BorderLayout.CENTER);
jtbOK = new JButton("确定");
button_pan = new JPanel();
button_pan.add(jtbOK);
loginframe.getContentPane().add(button_pan,BorderLayout.SOUTH);
loginframe.setSize(200,120);
loginframe.setVisible(true);
jtbOK.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
log();
}
});
}

//关闭
public void closeframe()
{
loginframe.setVisible(false);
loginframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
//得到管理员列表
public String[] getmanager()
{
dcon = new DATAConnection();
managerV = dcon.select("Select username from MACusers");
int count = managerV.size();
String[] s = new String[count];
for(int i = 0; i < count; i ++)
{
s[i] = ((Vector)managerV.get(i)).get(0).toString();
}
return s;
}
//log方法
public void log()
{
dcon = new DATAConnection();
JOptionPane jtp = new JOptionPane();
boolean flags = dcon.isNull("select * from MACusers where (username = '"+jcmbmanager.getSelectedItem().toString()+"' and password = '"+jtfpassword.getText()+"')");
while (!flags)
{
jtp.showMessageDialog(loginframe,"密码不正确,请重新输入");
}
username = jcmbmanager.getSelectedItem().toString();
loginframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
new MainFrame(username);
}
public String getusername()
{
return username;
}
}