JAVA：使用 XPath 表达式构建 XML 文档

使用XPath表达式构建XML文档是一种常见的JAVA编程技巧。XPath是一种用于在XML文档中定位节点的语言，它可以通过路径表达式选择XML文档中的节点。

java
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.newDocument();

java
XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
XPathExpression expression = xpath.compile("/root");
Element rootElement = (Element) expression.evaluate(document, XPathConstants.NODE);

java
Element childElement = document.createElement("child");
childElement.setAttribute("attribute", "value");
rootElement.appendChild(childElement);

java
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
StringWriter writer = new StringWriter();
transformer.transform(new DOMSource(document), new StreamResult(writer));
String xmlString = writer.getBuffer().toString();
System.out.println(xmlString);

java
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import java.io.StringWriter;
public class XPathExample {
    public static void main(String[] args) throws Exception {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document document = builder.newDocument();
        XPathFactory xPathfactory = XPathFactory.newInstance();
        XPath xpath = xPathfactory.newXPath();
        XPathExpression expression = xpath.compile("/root");
        Element rootElement = (Element) expression.evaluate(document, XPathConstants.NODE);
        Element childElement = document.createElement("child");
        childElement.setAttribute("attribute", "value");
        rootElement.appendChild(childElement);
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        StringWriter writer = new StringWriter();
        transformer.transform(new DOMSource(document), new StreamResult(writer));
        String xmlString = writer.getBuffer().toString();
        System.out.println(xmlString);
    }
}