老师为什么我都xml文档用schema限制后，运行xpath查询结果就不显示？？？

<?xml version="1.0" encoding="UTF-8"?>
<!-- 人力资源管理系统 -->
<hr xmlns="http://www.w3school.com.cn"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.w3school.com.cn  hr2.xsd">
    <employee id="e001">
        <name>张三</name>
        <age>31</age>
        <salary>4000</salary>
        <department>
            <dname>会计部</dname>
            <address>xx大厦-B103</address>
        </department>
    </employee>
    <employee id="e002">
        <name>李四</name>
        <age>41</age>
        <salary>5000</salary>
        <department>
            <dname>工程部</dname>
            <address>xx大厦-B303</address>
        </department>
    </employee>
    <employee id="e003">
        <name>王五</name>
        <age>55</age>
        <salary>10000</salary>
        <department>
            <dname>公关部</dname>
            <address>xx大厦-A001</address>
        </department>
    </employee>
</hr>

package com.mason.dom4j;

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

import java.util.List;

public class XPathTestor {
    public static void main(String[] args) {
        XPathTestor xPathTestor=new XPathTestor();
        xPathTestor.xpath("/hr/employee");
    }

    public void xpath(String xpathExp) {
        //传入参数为xPath表达式
        String file = "C:\\Users\\Mason\\IdeaProjects\\untitled\\src\\hr.xml";
        SAXReader reader = new SAXReader();
        try {
            Document document = reader.read(file);
            List<Node>nodes= document.selectNodes(xpathExp);
            for (Node node:nodes){
                Element emp=(Element) node;
                System.out.println(emp.elementText("name"));
                System.out.println(emp.elementText("age"));
                System.out.println(emp.elementText("salary"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

运行成功没用报错，但就是不显示结果！！这是为什么呢?

但我后来把xml的Schema限制删了之后↓

<?xml version="1.0" encoding="UTF-8"?>
<!-- 人力资源管理系统 -->
<hr>
    <employee id="e001">
        <name>张三</name>
        <age>31</age>
        <salary>4000</salary>
        <department>
            <dname>会计部</dname>
            <address>xx大厦-B103</address>
        </department>
    </employee>
    <employee id="e002">
        <name>李四</name>
        <age>41</age>
        <salary>5000</salary>
        <department>
            <dname>工程部</dname>
            <address>xx大厦-B303</address>
        </department>
    </employee>
    <employee id="e003">
        <name>王五</name>
        <age>55</age>
        <salary>10000</salary>
        <department>
            <dname>公关部</dname>
            <address>xx大厦-A001</address>
        </department>
    </employee>
</hr>

这样就可以正常显示出xpath后的结果，这是为什么呢？