关于NETBEANS连接数据库的问题

[JSW464618551]

run:
com.microsoft.sqlserver.jdbc.SQLServerException: 用户 'sa' 登录失败。
at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDatabaseError(Unknown Source)
at com.microsoft.sqlserver.jdbc.TDSTokenHandler.onEOF(Unknown Source)
at com.microsoft.sqlserver.jdbc.TDSParser.parse(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.sendLogon(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.logon(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.access$000(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection$LogonCommand.doExecute(Unknown Source)
at com.microsoft.sqlserver.jdbc.TDSCommand.execute(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.executeCommand(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.connectHelper(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.loginWithoutFailover(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.connect(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerDriver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at jdbctext.Main.getConn(Main.java:21)
at jdbctext.Main.main(Main.java:49)
java.lang.NullPointerException
at jdbctext.Main.main(Main.java:57)
成功生成（总时间：0 秒）











这是出现的问题

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/

package jdbctest;

import java.sql.Connection;
import java.sql.DriverManager;

/**
*
* @author Administrator
*/
public class Main {

private String url = "jdbc:sqlserver://localhost:1433;databaseName=MySchool";
public Connection getConn() throws Exception{
//加载驱动
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection conn = DriverManager.getConnection(url,"sa","sa");
return conn;
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
Main main = new Main();
Connection con = null;
try {
con = main.getConn();
if(con != null) {
System.out.println("数据库连接成功。");
}
}catch(Exception ex) {
ex.printStackTrace();
}finally {
try {
con.close();;
}catch(Exception ex) {
ex.printStackTrace();
}
}
}
}






这里是源码
谁能告诉我这是怎么情况啊，在线等，谢谢了