奇怪的错误。。

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;

import java.util.List;

public class XpathTester {
    public void xpath(String xpExp) {
        String file = "C:/My Work Material/idea/xml-work/src/plan.xml";
        SAXReader reader = new SAXReader();
        try {
            Document doc = reader.read(file);
            List<Node> nodes = doc.selectNodes(xpExp);
            for (Node node : nodes) {
                Element emp = (Element) node;
                System.out.println(emp.attributeValue("id"));
                System.out.println(emp.elementText("course-name"));
                System.out.println(emp.elementText("course-hour"));
                System.out.println(emp.elementText("exam-form"));
                System.out.println("= = = = = = = = = = = = = = = =");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        XpathTester xt = new XpathTester();
//        xt.xpath("//course");
    xt.xpath("/course[course-hour<50]");
    }

}

<?xml version="1.0" encoding="utf-8"?>
<teaching-plan xmlns="http://www.w3school.com.cn" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
               xsi:noNamespaceSchemaLocation="plan.xsd">
    <course id="001">
        <course-name>大学英语</course-name>
        <course-hour>36</course-hour>
        <exam-form>考试</exam-form>
    </course>
    <course id="002">
        <course-name>高等数学</course-name>
        <course-hour>70</course-hour>
        <exam-form>考试</exam-form>
    </course>
    <course id="003">
        <course-name>计算机应用基础</course-name>
        <course-hour>108</course-hour>
        <exam-form>上机考试</exam-form>
    </course>
    <course id="004">
        <course-name>体育课</course-name>
        <course-hour>52</course-hour>
        <exam-form>考试</exam-form>
    </course>
</teaching-plan>

C:\Jdk\jdk8\bin\java.exe "-javaagent:E:\Program Files\JetBrains\IntelliJ IDEA 2019.2.3\lib\idea_rt.jar=2610:E:\Program Files\JetBrains\IntelliJ IDEA 2019.2.3\bin" -Dfile.encoding=UTF-8 -classpath "C:\Jdk\jdk8\jre\lib\charsets.jar;C:\Jdk\jdk8\jre\lib\deploy.jar;C:\Jdk\jdk8\jre\lib\ext\access-bridge-64.jar;C:\Jdk\jdk8\jre\lib\ext\cldrdata.jar;C:\Jdk\jdk8\jre\lib\ext\dnsns.jar;C:\Jdk\jdk8\jre\lib\ext\jaccess.jar;C:\Jdk\jdk8\jre\lib\ext\jfxrt.jar;C:\Jdk\jdk8\jre\lib\ext\localedata.jar;C:\Jdk\jdk8\jre\lib\ext\nashorn.jar;C:\Jdk\jdk8\jre\lib\ext\sunec.jar;C:\Jdk\jdk8\jre\lib\ext\sunjce_provider.jar;C:\Jdk\jdk8\jre\lib\ext\sunmscapi.jar;C:\Jdk\jdk8\jre\lib\ext\sunpkcs11.jar;C:\Jdk\jdk8\jre\lib\ext\zipfs.jar;C:\Jdk\jdk8\jre\lib\javaws.jar;C:\Jdk\jdk8\jre\lib\jce.jar;C:\Jdk\jdk8\jre\lib\jfr.jar;C:\Jdk\jdk8\jre\lib\jfxswt.jar;C:\Jdk\jdk8\jre\lib\jsse.jar;C:\Jdk\jdk8\jre\lib\management-agent.jar;C:\Jdk\jdk8\jre\lib\plugin.jar;C:\Jdk\jdk8\jre\lib\resources.jar;C:\Jdk\jdk8\jre\lib\rt.jar;C:\My Work Material\idea\xml-work\out\production\xml-work;C:\My Work Material\idea\xml-work\lib\dom4j-2.1.1.jar" XpathTester

Exception in thread "main" java.lang.NoClassDefFoundError: org/jaxen/JaxenException

at org.dom4j.DocumentFactory.createXPath(DocumentFactory.java:222)

at org.dom4j.tree.AbstractNode.createXPath(AbstractNode.java:202)

at org.dom4j.tree.AbstractNode.selectNodes(AbstractNode.java:159)

at XpathTester.xpath(XpathTester.java:14)

at XpathTester.main(XpathTester.java:31)

Caused by: java.lang.ClassNotFoundException: org.jaxen.JaxenException

at java.net.URLClassLoader.findClass(URLClassLoader.java:381)

at java.lang.ClassLoader.loadClass(ClassLoader.java:424)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)

at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

... 5 more

Process finished with exit code 1