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

复制代码 代码如下:

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

复制代码 代码如下:

<?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">Learning XML</title>

<author>Erik T. Ray</author>

<year>2003</year>

<price>39.95</price>

</book>

</bookstore>

运行效果