java使用jndi的方法

try{      Context context=new InitalContext();      Context envCtx=(Contet)context.lookup("java:comp/env");      ds=(DataSource)envCtx.lookup("jdbc/bn");      if(ds!null)      {         out.println("已经获得DataSource!");         Connection conn=ds.getConnection();         Statement stmt=conn.createStatement();         ResultSet rst=stmt.executeQuery("select * from X");         out.print("已下是从数据库读出来的数据");         while(rs.next())         {           out.println(rst.getString("username"));         }        }       else         out.println("连接失败");        }      catch(Exception ne)         {          out.print(ne)         }