使用XPath读取XML文件以及使用Transformer改变XML节点值

最新推荐文章于 2022-07-12 20:44:50 发布

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文章标签：

#xml #xpath

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本文介绍如何利用XPath选择XML文件中的特定节点，并通过Transformer修改这些节点的值，详细阐述了XML处理的基本步骤和技术要点。

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book.xml

<?xml version="1.0" encoding="UTF-8"?>

<bookstore>

<book category="COOKING">
  <title lang="en">Everyday Italian</title>
  <author>Giada De Laurentiis</author>
  <year>2005</year>
  <price>30.00</price>
</book>

<book category="CHILDREN">
  <title lang="en">Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>

<book category="WEB">
  <title lang="en">XQuery Kick Start</title>
  <author>James McGovern</author>
  <author>Per Bothner</author>
  <author>Kurt Cagle</author>
  <author>James Linn</author>
  <author>Vaidyanathan Nagarajan</author>
  <year>2003</year>
  <price>49.99</price>
</book>

<book category="WEB">
  <title lang="en">Learning XML</title>
  <author>Erik T. Ray</author>
  <year>2003</year>
  <price>39.95</price>
</book>

</bookstore>

TestStax.java

<span style="font-size:14px;">package com.xml.stax;

import java.io.IOException;
import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.stream.EventFilter;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.XMLStreamWriter;
import javax.xml.stream.events.XMLEvent;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;

import org.junit.Test;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

public class TestStax {  
  
	
	@Test
	public void test6(){
		InputStream is = null;
		try {
			is = TestStax.class.getClassLoader().getResourceAsStream("books.xml");
			//创建文档处理对象
			DocumentBuilder db = DocumentBuilderFactory.newInstance().newDocumentBuilder();
			/**
			 *  XPath最有用的路径表达式
			 *  nodename 选取此节点的所有子节点 
			 *	/ 从根节点选取 
			 *	// 从匹配选择的当前节点选择文档中的节点，而不考虑它们的位置 
			 *	. 选取当前节点 
			 *	.. 选取当前节点的父节点 
			 *	@ 选取属性 
			 * */
			//通过DocumentBuilder 创建doc对象
			Document doc = db.parse(is);
			XPath path = XPathFactory.newInstance().newXPath();
			NodeList list = (NodeList)path.evaluate("//book[@category='WEB']", doc,XPathConstants.NODESET);
			for(int i = 0;i<list.getLength();i++){
				Element e = (Element)list.item(i);
				System.out.println(e.getElementsByTagName("title").item(0).getTextContent());
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			if(is != null){
				try {
					is.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
	
	@Test
	public void test7(){
		try {
			XMLOutputFactory factory = XMLOutputFactory.newInstance();
			//设置此属性可以写入命名空间 否则无法写入
			factory.setProperty("javax.xml.stream.isRepairingNamespaces", true);
			XMLStreamWriter writer = factory.createXMLStreamWriter(System.out);
			writer.writeStartDocument("UTF-8","1.0");
			writer.writeEndDocument();
			writer.writeStartElement("ns", "book", "http://w3c.school.com/1");
			writer.writeAttribute("category", "Web");
			writer.writeEndElement();
			writer.flush();
			writer.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	@Test
	public void test8(){
		InputStream is = null;
		try {
			is = TestStax.class.getClassLoader().getResourceAsStream("books.xml");
			DocumentBuilder db = DocumentBuilderFactory.newInstance().newDocumentBuilder();
			Document doc = db.parse(is);
			XPath path = XPathFactory.newInstance().newXPath();
			Transformer trans = TransformerFactory.newInstance().newTransformer();
			trans.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
			trans.setOutputProperty(OutputKeys.INDENT,"yes");
			NodeList list = (NodeList)path.evaluate("//book[title='Harry Potter']", doc,XPathConstants.NODESET);
			Element book = (Element)(list.item(0));
			Element price = (Element)(book.getElementsByTagName("price").item(0));
			price.setTextContent("400");
			Result result = new StreamResult(System.out);
			trans.transform(new DOMSource(doc),result);
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			if(is != null){
				try {
					is.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}</span>