在 Java 中计算xml文件上的xpath 示例

• 创建DocumentDOM 对象javax.xml.parsers.DocumentBuilder对象。
• 从 XPathFactory创建 XPath。
• 使用 xpath.evaluate('expression', dom, resultType)获取结果 HTML。

package com.onitroad.demo;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
public class XPathExample 
{
	public static void main(String[] args) throws Exception 
	{
		String xmlFile = "employees.xml";

		// 获取DOM
		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document xml = db.parse(xmlFile);
        // 获取 XPath 
        XPathFactory xpf = XPathFactory.newInstance();
        XPath xpath = xpf.newXPath();

        // 获取第1个匹配项
        String name = (String) xpath.evaluate("/employees/employee/firstName", xml, XPathConstants.STRING);

        System.out.println(name);	//JackLi

        // 获取所有的匹配项
        NodeList nodes = (NodeList) xpath.evaluate("/employees/employee/@id", xml, XPathConstants.NODESET);

        for (int i = 0; i < nodes.getLength(); i++) {
        	System.out.println(nodes.item(i).getNodeValue());	//1 2
        }
    }
}

测试使用的XML文件

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<employees>
    <employee id="1">
        <firstName>JackLi</firstName>
        <lastName>Gupta</lastName>
        <department>
            <id>101</id>
            <name>IT</name>
        </department>
    </employee>
    <employee id="2">
        <firstName>BobRobert</firstName>
        <lastName>Schultz</lastName>
        <department>
            <id>102</id>
            <name>HR</name>
        </department>
    </employee>
</employees>