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
Everyday Italian Giada De Laurentiis 2005 30.00 Harry Potter J K. Rowling 2005 29.99 Learning XML Erik T. Ray 2003 39.95
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