sql 与java 连接不上的原因谁知道?

package bean;

import java.sql.*;

public class Admin
{
String DBDriver="sun.jdbc.odbc.JdbcOdbcDriver";
String DBUrl="jdbc:odbc:sj_test";//建立了sj_test的数据源

private Connection conn=null;
private Statement stmt=null;
ResultSet rs=null;

public Admin(){
try{//注册
Class.forName(DBDriver);
}

catch(java.lang.ClassNotFoundException e)
{
System.err.println("出错啦！！数据库注册出毛病了！！！"+e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{ rs=null;
try{//连接数据库查询
conn=DriverManager.getConnection(DBUrl,"用户名","密码");
stmt=conn.createStatement();
rs=stmt.executeQuery(sql);
}
catch(SQLException ex)
{
System.err.println("暂时无法连接数据库！！"+ex.getMessage());
}
return rs;
}

public void e