<?xml version="1.0" encoding="UTF-8"?>

<student>
    <stu>
        <id>100</id>
        <name>zhangsan</name>
        <age>20</age>
    </stu>
    <stu>
        <id>101</id>
        <name>wangwu</name>
        <age>40</age>
    </stu>
</student>

package vo_;

public class Student {
    private String id;
    private String name;
    private String age;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
    }

}

package service;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import vo_.Student;

import java.io.FileOutputStream;
import java.util.List;

public class StuService {

    //增加
    public static void add(Student student) throws Exception {
        //创建解析器
        SAXReader saxReader = new SAXReader();
        //得到document
        Document document = saxReader.read("src/student.xml");
        //得到根节点
        Element rootElement = document.getRootElement();
        //在根节点上添加stu
        Element stu = rootElement.addElement("stu");
        //在stu上添加id name age 标签
        Element id1 = stu.addElement("id");
        Element name1 = stu.addElement("name");
        Element age1 = stu.addElement("age");
        //在ID name age 上添加值
        id1.setText(student.getId());
        name1.setText(student.getName());
        age1.setText(student.getAge());
        //回写xml
        OutputFormat format = OutputFormat.createPrettyPrint();
        XMLWriter xmlWriter = new XMLWriter(new FileOutputStream("src/student.xml"), format);
        xmlWriter.write(document);
        xmlWriter.close();
    }

    //删除根据学生的id删除
    public static void delStu(String id) throws Exception {
        //创建解析器
        SAXReader saxReader = new SAXReader();
        //得到document
        Document document = saxReader.read("src/student.xml");
        //获取所有的id xpath：//id
        List<Node> list = document.selectNodes("//id");
        //遍历list集合
        for (Node node :
                list) {//node是每个id的元素
            //得到id的值
            String idv = node.getText();
            //判断idv和id是否相等
            if (idv.equals(id)) {
                //id相同
                Element stu = node.getParent();
                //获取stu的父节点
                Element student = stu.getParent();
                student.remove(stu);
            }

        }
        //回写
        OutputFormat format = OutputFormat.createPrettyPrint();
        XMLWriter xmlWriter = new XMLWriter(new FileOutputStream("src/student.xml"), format);
        xmlWriter.write(document);
        xmlWriter.close();
    }

    //查询,根据id查询学生信息
    public static Student getStu(String id) throws Exception {
        //创建一个student对象
        Student student = new Student();
        //创建解析器
        SAXReader saxReader = new SAXReader();
        //得到document
        Document document = saxReader.read("src/student.xml");
        //获取所有的id xpath：//id
        List<Node> list = document.selectNodes("//id");
        for (Node node : list) {//node是每个id的节点
            //得到id的值
            String idv = node.getText();
            if (idv.equals(id)) {
                Element stu = node.getParent();
                //通过stu获得age和name
                String namev = stu.element("name").getText();
                String agev = stu.element("age").getText();
                student.setAge(agev);
                student.setName(namev);
                student.setId(idv);
            }
        }
        return student;
    }
}

package test;

import service.StuService;
import vo_.Student;

public class TestStu {
    public static void main(String[] args) throws Exception {
        testAdd();
//        testDel();
//        testStr();
    }

    //测试添加方法
    public static void testAdd() throws Exception {
        Student stu = new Student();
        stu.setAge("103");
        stu.setName("wangwu");
        stu.setAge("40");
        StuService.add(stu);
    }

    //测试删除方法
    public static void testDel() throws Exception {
        StuService.delStu("101");
    }

    //测试查询方法
    public static void testStr() throws Exception {//查询id为100的信息
        Student stu = StuService.getStu("100");
        System.out.println(stu.toString());
    }
}