外行请问jsp数据库链接500异常

外行请教jsp数据库链接500错误.
偶不懂JSP,公司JSP程序员走了,让偶配置JSP站点.花了1周才把环境搞好.现在又出500错误.请各路神仙帮忙.

数据库链接代码:
package   cn.com.dateConn;

import   java.sql.*;

public   class   DateConnSql   {
      private   static   Connection   conn   =   null;

      public   static   Connection   getInstance()   {
            if(conn   ==   null)  
                      new   DateConnSql();
            return   conn;
      }
      private   DateConnSql()   {
try   {
Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver ");
}   catch   (ClassNotFoundException   e1)   {
//   TODO   Auto-generated   catch   block
e1.printStackTrace();
}

          try   {
conn=DriverManager.getConnection( "jdbc:odbc:mydata ");
}   catch   (SQLException   e)   {
//   TODO   Auto-generated   catch   block
e.printStackTrace();
}
      }
}    

}

root   cause  

java.lang.NullPointerException
cn.com.dateConn.PageConn.executeQuery(PageConn.java:21)

//第21行就是conn=DriverManager.getConnection( "jdbc:odbc:mydata ");


note   The   full   stack   trace   of   the   root   cause   is   available   in   the   Apache   Tomcat/5.5.12   logs.


--------------------------------------------

Apache   Tomcat/5.5.12

------解决方案--------------------
得配置ODBC mydata
------解决方案--------------------
conn=DriverManager.getConnection( "jdbc:odbc:mydata ");

mydata是什么？数据库连接的原理是下面这个：

Connection conn = DriverManager.getConnection( "jdbc:oracle:thin:@192.168.1.1:1521:ora9i ", "name ", "password ");

这是连接oracle的，jdbc:oracle:thin:@是固定的，然后跟着ip地址，然后是用户名和密码
------解决方案--------------------
从错误信息上来看，你的错误不是这个类的，应该是别的类的，可能 pageConn中的executeQuery方法出了问题
------解决方案--------------------
我给你写了个类你试一下,希望能帮到你
import java.sql.*;
public class DB {
private Connection con=null;
private Statement stmt=null;
private ResultSet rs=null;
//url= "jdbc:odbc:first ";
//Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver ");
//con=DriverManager.getConnection(url, "sa ", " ");
String DBDriver= "sun.jdbc.odbc.JdbcOdbcDriver ";
String url= "jdbc:odbc:Test ";
public DB()
{
try
{
Class.forName(DBDriver);

}
catch (ClassNotFoundException e)
{

System.out.println( "opendb: "+e.getMessage());
}

}
public ResultSet excuteQuery(String sql)
{
try
{
con=DriverManager.getConnection(url, "sa ", " ");
stmt=con.createStatement();
rs=stmt.executeQuery(sql);
}
catch (SQLException e)
{
System.out.println( "executeQueryerr: "+e.getMessage());