Java uses xpath to parse xml example sharing

XPath is XML Path Language, which is a language used to determine the location of certain parts of XML documents. XPath is based on the tree structure of XML and provides the ability to find nodes in the data structure tree. The original intention of XPath was to serve as a universal syntax model between XPointer and XSL. But XPath was quickly adopted by developers as a small query language.

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

<?xml version="1.0" encoding="utf-8" ?>
<bookstore>
 <book category="COOKING">
   <title>Everyday Italian</title> 
   <author>Giada De Laurentiis</author> 
   <year>2005</year> 
   <price>30.00</price> 
 </book>
 <book category="CHILDREN">
   <title>Harry Potter</title> 
   <author>J K. Rowling</author> 
   <year>2005</year> 
   <price>29.99</price> 
 </book>
 <book category="WEB">
   <title>Learning XML</title> 
   <author>Erik T. Ray</author> 
   <year>2003</year> 
   <price>39.95</price> 
 </book>
</bookstore>

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