http调用接口，并解析返回的xml数据，显示在jsp页面上
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import="java.util.*"%>
<%@ page import="java.net.URL"%>
<%@ page import="javax.xml.parsers.DocumentBuilderFactory"%>
<%@ page import="javax.xml.parsers.DocumentBuilder"%>
<%@ page import="org.w3c.dom.Element"%>
<%@ page import="org.w3c.dom.NodeList"%>
<%@ page import="org.w3c.dom.Document"%>
<%@ page import="java.net.URLConnection"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>查询商品大类</title>
</head>
<body>
