Java 8 xpath 示例 - 评估字符串的 xpath

评估字符串的 xpath 并在字符串本身中返回结果 XML 的 Java 示例。

1. XPath 示例——在 xml 字符串上计算 xpath

1. 创建包含 org.xml.sax.InputSource 的 StringReader 引用 XML 字符串。
2. 从 XPath 创建 XPathFactory。
3. 使用 xpath.evaluate('expression', inputSource) 获取结果 HTML。

package com.cundage.demo;

import java.io.StringReader;

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;
import org.xml.sax.InputSource;

public class XPathExample 
{
	public static void main(String[] args) throws Exception 
	{

		String xml = "<employees>"
					+ "<employee id=\"1\">"
						+ "<firstName>Lokesh</firstName>"
						+ "<lastName>Gupta</lastName>"
						+ "<department><id>101</id><name>IT</name></department>"
					+ "</employee>"
				   + "</employees>";
		
		InputSource inputXML = new InputSource( new StringReader( xml ) );
		
        XPath xPath = XPathFactory.newInstance().newXPath();
        
        String result = xPath.evaluate("/employees/employee/firstName", inputXML);

        System.out.println(result);
    }
}

程序输出：

Lokesh

2. XPath 示例——在 xml 文件上计算 xpath

package com.cundage.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";
		
		//Get DOM
		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document xml = db.parse(xmlFile);

        //Get XPath 
        XPathFactory xpf = XPathFactory.newInstance();
        XPath xpath = xpf.newXPath();
        
        //Get first match
        String name = (String) xpath.evaluate("/employees/employee/firstName", xml, XPathConstants.STRING);
        
        System.out.println(name);	//Lokesh
        
        //Get all matches
        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
        }
    }
}

程序输出：

Lokesh
1
2

输入的 xml 文件是：

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

在上面的 Xpath 教程中，我们学习了如何通过示例评估字符串上的 xpath。

快乐学习！！

更多参考：

Java xpath 文件示例
Java xpath 教程
如何在 java 中使用 xpath 获取 xml 中的属性值

标签2： Java XML XPath

地址：https://www.cundage.com/article/evaluate-xpath-on-xml-string.html