private  DataSource getJdbcConnectionPool()  throws  NamingException {
        Context c= new  InitialContext();
         return  (DataSource) c.lookup("java:comp/env/jdbc/connectionPool");
    }  

        
Connection connection= null ;
         try  {
            // connect to database
            String sql="SELECT FROM..";
            DataSource dataSource=getJdbcConnectionPool();
            connection=dataSource.getConnection();
            PreparedStatement stat=connection.prepareStatement(sql);
            ................
        }  catch (Exception e){
            System.out.println(e.getMessage());
        }