<Context>   
<Resource
name="oracle-10g"
auth="Container"
type="javax.sql.DataSource"
driverClassName="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:thin:@127.0.0.1:1521:XE"
username="wind"
password="wind"
connectionProperties="SetBigStringTryClob=true"
maxActive="25"
maxIdle="5"
maxWait="10000"
/>
</Context>    

<resource-ref>
<res-ref-name>oracle-10g</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>

 public   void  doGet(HttpServletRequest request,
                  HttpServletResponse response)
         throws  IOException, ServletException
{
    Context env =  null ;
     try  {
        env = (Context)  new  InitialContext().lookup("java:comp/env");
        pool = (DataSource) env.lookup("oracle-10g");
         if (pool ==  null )
         throw   new  Exception("OracleXE неизвестный источник");
    }  catch  (Exception e){
        System.out.println(e);
    }
     if  (pool !=  null )
    {
        System.out.println("Соединение может происходить настройка найдена");
        Connect();
    }

}

     private   void  Connect() {
        Connection conn =  null ;
                Statement stmp =  null ;
                ResultSet rs =  null ;
                ResultSetMetaData rsm = null ;
                String sql = "select * from dual";

                     try  {
                        conn = pool.getConnection();
                    }  catch  (SQLException e) {
                        e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
                    }
         try {
                    stmp = conn.createStatement();
                    rs = stmp.executeQuery(sql);
                    rsm = rs.getMetaData();
                     int  colCount = rsm.getColumnCount();
        } catch  (SQLException e)
        {
            e.printStackTrace();
        }

    }

 1 . Cannot create JDBC driver of  class  ''  for  connect URL 'null'
 2 . Caused by: java.sql.SQLException: No suitable driver