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