整个系统的结构是这个样子的。
总共大概三百行代码，供初学者学习。

<?xml version="1.0" encoding="UTF-8" standalone="no"?><exam><student examid="1111" idcard="5555"><name>张三</name><location>上海</location><grade>9</grade></student><student><name>李四</name><location>大连</location><grade>97</grade></student>
</exam>

//StudentDao.java
package cn.itcast.dao;import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;import cn.itcast.domain.Student;
import cn.itcast.utils.XmlUtils;/*** <student examid="222" idcart="111"><name>张三</name><location>沈阳</location><grade>89</grade></student>* @author Logan**/
public class StudentDao {public void add(Student student){try{Document document = XmlUtils.getDocument();//student_node  //ctrl+1 rename in fileElement student_node = document.createElement("student");student_node.setAttribute("examid", student.getExamid());student_node.setAttribute("idcard", student.getIdcard());Element name = document.createElement("name");name.setTextContent(student.getName());Element location = document.createElement("location");location.setTextContent(student.getLocation());Element grade = document.createElement("grade");grade.setTextContent(student.getGrade()+"");student_node.appendChild(name);student_node.appendChild(location);student_node.appendChild(grade);//得到exam节点，并把student挂上去document.getElementsByTagName("exam").item(0).appendChild(student_node);XmlUtils.write2Xml(document);}catch(Exception e){throw new RuntimeException(e);}}//删除public void delete(String name){try{Document document = XmlUtils.getDocument();NodeList list = document.getElementsByTagName("name");for(int i = 0;i<list.getLength();i++){if(list.item(i).getTextContent().equals(name)){list.item(i).getParentNode().getParentNode().removeChild(list.item(i).getParentNode());XmlUtils.write2Xml(document);return;}}throw new RuntimeException("对不起，您要删除的学生不存在！");//异常也是一种返回值 }catch(Exception e){throw new RuntimeException(e);}}//查找public Student find(String examid){try{Document document = XmlUtils.getDocument();NodeList list = document.getElementsByTagName("student");Student student = new Student();for(int i = 0;i<list.getLength();i++){Element student_node = (Element) list.item(i);if(student_node.getAttribute("examid").equals(examid)){Student s = new Student();s.setExamid(examid);student.setExamid(student_node.getAttribute("examid"));student.setIdcard(student_node.getAttribute("idcard"));s.setName(student_node.getElementsByTagName("name").item(0).getTextContent());s.setGrade(Double.parseDouble(student_node.getElementsByTagName("grade").item(0).getTextContent()));s.setLocation(student_node.getElementsByTagName("location").item(0).getTextContent());return s;}}return null;}catch(Exception e){throw new RuntimeException(e);}}}

//Student.java
package cn.itcast.domain;public class Student {private String idcard;private String examid;private String name;private String location;private Double grade;//alt+shift+spublic String getIdcard() {return idcard;}public void setIdcard(String idcard) {this.idcard = idcard;}public String getExamid() {return examid;}public void setExamid(String examid) {this.examid = examid;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getLocation() {return location;}public void setLocation(String location) {this.location = location;}public double getGrade() {return grade;}public void setGrade(double grade) {this.grade = grade;}
}

//XmlUtils.java
package cn.itcast.utils;import java.io.File;
import java.io.IOException;import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;import org.w3c.dom.Document;
import org.xml.sax.SAXException;public class XmlUtils {public static Document getDocument() throws ParserConfigurationException, SAXException, IOException{DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder builder = factory.newDocumentBuilder();return builder.parse(new File("src/student.xml"));}public static void write2Xml(Document document) throws TransformerException{TransformerFactory factory = TransformerFactory.newInstance();Transformer tf = factory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new File("src/student.xml")));}}

//Main.java
package cn.itcast.view;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;import cn.itcast.dao.StudentDao;
import cn.itcast.domain.Student;public class Main {public static void main(String[] args) throws IOException {// TODO Auto-generated method stubSystem.out.println("添加学生(a)  查找学生(b)  删除学生(c)");System.out.print("请输入操作类型:");BufferedReader br = new BufferedReader(new InputStreamReader(System.in));String type = br.readLine();if(type.equalsIgnoreCase("a")){//添加学生try{System.out.print("请输入学生姓名：");String name = br.readLine();System.out.print("请输入学生准考证号：");String examid = br.readLine();System.out.print("请输入学生身份证号：");String idcard = br.readLine();System.out.print("请输入学生所在地：");String location = br.readLine();System.out.print("请输入学生成绩：");String grade = br.readLine();Student student = new Student();student.setExamid(examid);student.setGrade(Double.parseDouble(grade));student.setIdcard(idcard);student.setLocation(location);student.setName(name);StudentDao dao = new StudentDao();dao.add(student);System.out.println("恭喜，添加成功！");}catch(Exception e){System.out.println("对不起，录入失败！");}}else if(type.equalsIgnoreCase("b")){//查找学生System.out.print("请输入查找的学生准考证号：");String examid = br.readLine();StudentDao dao = new StudentDao();Student student = dao.find(examid);if(student==null){System.out.println("对不起，您要查找的学生不存在！");}else{System.out.println("姓名："+student.getName()+",身份证号：" +student.getIdcard()+",准考证号:"+student.getExamid()+",地区:"+student.getLocation()+",成绩:"+student.getGrade());}}else if(type.equalsIgnoreCase("c")){//删除学生try{System.out.print("请输入删除的学生姓名：");String name = br.readLine();StudentDao dao = new StudentDao();dao.delete(name);System.out.println("已删除"+name);System.out.println("恭喜您，删除成功！");}catch(Exception e){System.out.println(e.getMessage());}}else{System.out.println("非法字符");}}
}

该项目也可以使用DOM4j的API实现
下面是部分代码

//StudentDaoWithDOM4j
package cn.itcast.dao;import java.util.ArrayList;
import java.util.List;import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;import cn.itcast.domain.Student;
import cn.itcast.utils.XmlUtilWithDom4j;
public class StudentDaoByDom4j {public void add(Student student) throws Exception{Document document = XmlUtilWithDom4j.getdocument();Element root = document.getRootElement();Element student_element = DocumentHelper.createElement("student");Element name_element = DocumentHelper.createElement("name");Element location_element = DocumentHelper.createElement("location");Element grade_element = DocumentHelper.createElement("grade");//student_element.addElement("name").setText(student.getName());这种方法也是可以的。name_element.setText(student.getName());location_element.setText(student.getLocation());grade_element.setText(student.getGrade()+"");student_element.addAttribute("examid", student.getExamid());student_element.addAttribute("idcard", student.getIdcard());student_element.add(name_element);student_element.add(location_element);student_element.add(grade_element);root.add(student_element);XmlUtilWithDom4j.write2xml(document);}public void delete(String name) throws Exception{Document document = XmlUtilWithDom4j.getdocument();Element root = document.getRootElement();List list = document.getRootElement().elements("student");for(int i = 0;i<list.size();i++){Element student_element = (Element) list.get(i);if(student_element.element("name").getText().equals(name)){root.remove(student_element);}}XmlUtilWithDom4j.write2xml(document);}public Student find(String examid) throws Exception{Document document = XmlUtilWithDom4j.getdocument();Element root = document.getRootElement();Student student = new Student();List list = document.getRootElement().elements("student");for(int i = 0;i<list.size();i++){Element student_element = (Element) list.get(i);if(student_element.attributeValue("examid").equals(examid)){student.setExamid(examid);student.setIdcard(student_element.attributeValue("idcard"));student.setGrade(Double.parseDouble(student_element.element("grade").getText()));student.setLocation(student_element.element("location").getText());student.setName(student_element.element("name").getText());return student;}}return null;}}

//XmlUtilWithDOM4j
package cn.itcast.utils;import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.UnsupportedEncodingException;import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;public class XmlUtilWithDom4j {public static Document getdocument() throws Exception{SAXReader reader = new SAXReader();Document document = reader.read(new File("src/student.xml"));return document;}public static void write2xml(Document document) throws Exception, FileNotFoundException{OutputFormat format = OutputFormat.createPrettyPrint();format.setEncoding("UTF-8");XMLWriter writer = new XMLWriter(new FileOutputStream("src/student.xml"));writer.write(document);writer.close();}}