求助，java连接sql server2008出错！com.microsoft.jdbc.sqlserver.SQLServerDriver

附代码：

数据库连接类
package classsource;

import java.sql.*;

public class Database {
public static Connection cn;
public static Statement st;
public static ResultSet rs;

public static boolean joinDB() {
boolean joinFlag;
try {
joinFlag = true;
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
cn = DriverManager.getConnection("jdbc:microsoft:sqlserver://localhost:1433; DatabaseName=EmployeeInformationMS","sa","admin12");

cn.setCatalog("EmployeeInformationMS");
System.out.println("数据库连接成功");
st = cn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_READ_ONLY);
return joinFlag;

} catch (SQLException sqlEx) {
System.out.println(sqlEx.getMessage());

joinFlag = false;
return joinFlag;

} catch (ClassNotFoundException notfoundEX) {
System.out.println(notfoundEX.getMessage());

joinFlag = false;
return joinFlag;
}
}

public static boolean executeSQL(String sqlString) {
boolean executeFlag;
try {
st.execute(sqlString);
executeFlag = true;
} catch (Exception e) {
executeFlag = false;
System.out.println("sql exception:" + e.getMessage());
}
return executeFlag;
}


public static boolean query(String sqlString) {

try {
rs = null;
//System.out.println(sqlString);
rs = st.executeQuery(sqlString);
} catch (Exception Ex) {
System.out.println("sql exception:" + Ex);
return false;
}
return true;
}
}

//用户登陆类


package classsource;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.sql.*;

public class Land extends JFrame{
JFrame jf ;

JTextField textName=new JTextField();
JPasswordField textage=new JPasswordField();

JLabel label = new JLabel("员工管理系统");
JLabel labelName=new JLabel("用户名：");
JLabel labelage=new JLabel("密码：");


JButton buttonEnter=new JButton("登录");
JButton buttoncancel=new JButton("清空");

public Land(){
jf=this;
setTitle("登录");
Font f = new Font("新宋体",Font.PLAIN,12);
Container con = getContentPane();
con.setLayout(null);
label.setBounds(95,10,110,20);
label.setFont(new Font("新宋体",Font.PLAIN,14));
con.add(label);
labelName.setBounds(45,40,55,20);
labelName.setFont(f);
con.add(labelName);
textName.setBounds(95,40,120,20);
con.add(textName);

labelage.setBounds(45,70,45,20);
con.add(labelage);
labelage.setFont(f);
textage.setBounds(95,70,120,20);
con.add(textage);



buttonEnter.setBounds(90,110,60,20);
buttonEnter.setFont(f);
con.add(buttonEnter);

//登陆的鼠标监听

buttonEnter.addMouseListener(new MouseAdapter(){
public void mouseClicked(MouseEvent me){
if(textName.getText().equals("")){
new JOptionPane().showMessageDialog(null,"用户名不能为空!");
}
else if(textage.getText().equals("")){
new JOptionPane().showMessageDialog(null,"密码不能为空!");
}
else{
String sql="select * from UserInformation where User_Name = '" + textName.getText() + "' and Password = '" + textage.getText()+ "'";
System.out.println(sql);
Judge(sql);
}
}
});

buttoncancel.setBounds(155,110,60,20);
buttoncancel.setFont(f);
con.add(buttoncancel);

//清空按钮的鼠标监听方法
buttoncancel.addMouseListener(new MouseAdapter(){
public void mouseClicked(MouseEvent me){
textName.setText("");
textage.setText("");
}
});

setResizable(false);
//窗口图标
Image img=Toolkit.getDefaultToolkit().getImage("image\\main.gif");
setIconImage(img);
Toolkit t = Toolkit.getDefaultToolkit();
int w = t.getScreenSize().width;
int h = t.getScreenSize().height;
setBounds(w/2-150,h/2-90,300,180);
setVisible(true);
}

private void Judge(String sqlString) {

if (Database.joinDB()) {
if (Database.query(sqlString))
try{
if(Database.rs.isBeforeFirst()) {
System.out.println("密码正确");
jf.setVisible(false);
//关闭数据库连接
Database.cn.close();
new Main();
}
else {
System.out.println("错误");
new JOptionPane().showMessageDialog(null,"用户名或密码错误!","",JOptionPane.ERROR_MESSAGE);//!!!!!!!!!!!!!!
}
}catch(Exception ex) {
System.out.println(ex.getMessage());
}
}
else{
System.out.println("连接数据库不成功!!!");
}
}

public static void main(String args[]){
new Land();
}
}


需要主函数类的话我再上传