Java xpath 示例 – 在 xml 文件上求值 xpath · HowToDoInJava 中文系列教程

# Java xpath 示例 – 在 xml 文件上求值 xpath > 原文： [https://howtodoinjava.com/xml/evaluate-xpath-on-dom/](https://howtodoinjava.com/xml/evaluate-xpath-on-dom/) **Java xpath 示例**讀取 XML 文件并解析為 DOM 對象，然后**求值`org.w3c.dom.Document`對象**上的 xpath 并以`String`或`NodeList`的形式獲取結果。 ## 1\. Java 求值 xml 文件上的 xpath 1. 創建`Document` DOM 對象`javax.xml.parsers.DocumentBuilder`對象。 2. 從[`XPathFactory`](https://docs.oracle.com/javase/8/docs/api/javax/xml/xpath/XPathFactory.html)創建[`XPath`](https://docs.oracle.com/javase/8/docs/api/javax/xml/xpath/XPath.html)。 3. 使用[`xpath.evaluate('expression', dom, resultType)`](https://docs.oracle.com/javase/8/docs/api/javax/xml/xpath/XPath.html#evaluate-java.lang.String-org.xml.sax.InputSource-)獲取結果 HTML。 ```java package com.howtodoinjava.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 } } } ``` 程序輸出： ```java Lokesh 1 2 ``` ## 2\. XML 文件輸入的 xml 文件為： ```java <?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> ``` 學習愉快！閱讀更多： [字符串中的 Java xpath 示例](https://howtodoinjava.com/xml/evaluate-xpath-on-xml-string/) [Java xpath 教程](https://howtodoinjava.com/xml/how-to-work-with-xpaths-in-java-with-examples/) [如何在 Java 中使用 xpath 獲取 xml 中的屬性值](https://howtodoinjava.com/xml/xpath-attribute-evaluate/)