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XPath即为XML路径语言(XML Path Language)，它是一种用来确定XML文档中某部分位置的语言。XPath基于XML的树状结构，提供在数据结构树中找寻节点的能力。起初 XPath 的提出的初衷是将其作为一个通用的、介于XPointer与XSL间的语法模型。但是 XPath 很快的被开发者采用来当作小型查询语言。

XPathTest.java

package com.hongyuan.test;

import java.io.File;import java.io.IOException;

import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.ParserConfigurationException;import javax.xml.xpath.XPath;import javax.xml.xpath.XPathConstants;import javax.xml.xpath.XPathExpressionException;import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;import org.w3c.dom.Node;import org.w3c.dom.NodeList;import org.xml.sax.SAXException;

public class XPathTest {

public static void main(String[] args) throws ParserConfigurationException,   SAXException, IOException, XPathExpressionException {

// 解析文件，生成document对象  DocumentBuilder builder = DocumentBuilderFactory.newInstance()    .newDocumentBuilder();  Document document = builder.parse(new File("bookstore.xml"));

// 生成XPath对象  XPath xpath = XPathFactory.newInstance().newXPath();

// 获取节点值  String webTitle = (String) xpath.evaluate(    "/bookstore/book[@category='WEB']/title/text()", document,    XPathConstants.STRING);  System.out.println(webTitle);

System.out.println("===========================================================");

// 获取节点属性值  String webTitleLang = (String) xpath.evaluate(    "/bookstore/book[@category='WEB']/title/@lang", document,    XPathConstants.STRING);  System.out.println(webTitleLang);

System.out.println("===========================================================");

// 获取节点对象  Node bookWeb = (Node) xpath.evaluate(    "/bookstore/book[@category='WEB']", document,    XPathConstants.NODE);  System.out.println(bookWeb.getNodeName());

System.out.println("===========================================================");

// 获取节点集合  NodeList books = (NodeList) xpath.evaluate("/bookstore/book", document,    XPathConstants.NODESET);  for (int i = 0; i < books.getLength(); i++) {   Node book = books.item(i);   System.out.println(xpath.evaluate("@category", book,     XPathConstants.STRING));  }

System.out.println("==========================================================="); }

}

bookstore.xml

Giada De Laurentiis

2005

30.00

J K. Rowling

2005

29.99

Erik T. Ray

2003

39.95

运行效果