无法通过带有getNodeValue函数的xpath获取节点值

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

public class XPathExample {
    public static void main(String[] args) {
        try {
            // 创建一个DocumentBuilderFactory对象
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
            
            // 解析XML文件并获取Document对象
            Document doc = builder.parse("example.xml");
            
            // 创建XPathFactory对象
            XPathFactory xPathfactory = XPathFactory.newInstance();
            XPath xpath = xPathfactory.newXPath();
            
            // 编写XPath表达式
            String expression = "/root/element";
            
            // 使用XPath表达式获取节点列表
            NodeList nodeList = (NodeList) xpath.evaluate(expression, doc, XPathConstants.NODESET);
            
            // 遍历节点列表并获取每个节点的值
            for (int i = 0; i < nodeList.getLength(); i++) {
                System.out.println(nodeList.item(i).getTextContent());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}