对XML文件进行的添加、删除、修改、查询操作。

ui 表现层：StudentUI2 代码如下：

package test2.ui;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.PrintWriter;
import java.util.Scanner;
import test2.dao.StudentDao;
import test2.domain.Student;

//表现层
public class StudentUI2 {
public static void main(String[] args) throws Exception {
add();
}

// 修改
public static void update() throws Exception {
Scanner scanner = new Scanner(System.in);
System.out.println("输入要修改的编号：");
String id = scanner.nextLine();
System.out.println("输入要修改后的姓名：");
String name = scanner.nextLine();
System.out.println("输入要修改的年龄：");
String age = scanner.nextLine();
Student stu = new Student();
stu.setId(id);
stu.setAge(age);
stu.setName(name);
new StudentDao().update(stu);
}
//  读取
public static void read() throws Exception {
Scanner scanner = new Scanner(System.in);
System.out.println("输入要查询的编号：");
String id = scanner.nextLine();
new StudentDao().read(id);
}
// 删除
public static void delete() throws Exception {
Scanner scanner = new Scanner(System.in);
System.out.println("输入要删除的编号：");
String id = scanner.nextLine();
new StudentDao().delete(id);

}
// 添加
public static void add() throws Exception {
Scanner scanner = new Scanner(System.in);
// 文件中存储的是当前添加对象的id值
File f = new File("src/test2/ui/id.txt");
BufferedReader bf = new BufferedReader(new FileReader(f));

String id = bf.readLine();
System.out.println("姓名：");
String name = scanner.nextLine();
System.out.println("年龄：");
String age = scanner.nextLine();

// 封装成java对象
Student student = new Student();
student.setId(id);
student.setName(name);
student.setAge(age);
// 调用Dao对象
StudentDao studao = new StudentDao();
boolean flag = studao.create(student);
if (flag) {
System.out.println("操作成功！");
//更新存储id的文本的值
f.delete();
PrintWriter pw = new PrintWriter(f);
pw.println(Integer.parseInt(id) + 1);
pw.flush();
pw.close();
} else {
System.out.println("操作失败！");
}
}
}

dao 访问层：StudentDao

package test2.dao;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

import test2.domain.Student;
//访问层
public class StudentDao {
//修改元素
public void update(Student stu) throws Exception{
String xpath = "//student[@id='"+stu.getId()+"']";
Document doc = readxml();
//获取符合条件的元素
Element ele = (Element) doc.selectSingleNode(xpath);
if(ele != null){
ele.element("name").setText(stu.getName());
ele.element("age").setText(stu.getAge());
write2XML(doc);
}else{
System.out.println("不存在！");
}

}

//查询元素
public void read(String id) throws Exception{
String xpath = "//student[@id='"+id+"']";
Document doc = readxml();
Element ele = (Element) doc.selectSingleNode(xpath);
if(ele != null){
System.out.println("编号："+ele.attributeValue("id"));
System.out.println("姓名："+ele.elementText("name"));
System.out.println("年龄："+ele.elementText("age"));
}else{
System.out.println("不存在！");
}
}

//删除元素
public void delete(String id) throws IOException, UnsupportedEncodingException, IOException{
String xpath = "//student[@id='"+id+"']";
Document doc = readxml();
Element ele = (Element) doc.selectSingleNode(xpath);
if(ele != null){
//父节点删除子节点
ele.getParent().remove(ele);
write2XML(doc);
System.out.println("删除成功！");
}else{
System.out.println("不存在！");
}
}

//添加元素
public boolean create(Student student) throws Exception{
boolean flag = false;
if(student !=null){
Document doc = readxml();
Element rootele = doc.getRootElement();
Element studentele = rootele.addElement("student");
studentele.addAttribute("id", student.getId());
studentele.addElement("name").setText(student.getName());
studentele.addElement("age").setText(student.getAge());
write2XML(doc);
flag=true;
}
return flag;
}

//读取硬盘中的xml文件到内存中
private Document readxml() {
SAXReader sax = new SAXReader();
Document doc = null;
try {
doc = sax.read(new File("src/test2/db/Student.xml"));
} catch (DocumentException e) {
doc = DocumentHelper.createDocument();
doc.addElement("student");
}
return doc;
}
//将内存中的xml写到文本硬盘文本中
private void write2XML(Document doc) throws FileNotFoundException,
UnsupportedEncodingException, IOException {
OutputFormat opf = OutputFormat.createPrettyPrint();
OutputStream os = new FileOutputStream("src/test2/db/Student.xml");
XMLWriter xmlwriter = new XMLWriter(os,opf);
xmlwriter.write(doc);
xmlwriter.close();
}
}

Student.xml数据层:

<?xml version="1.0" encoding="UTF-8"?>
<students>
<student id="1">
<name>jerry</name>
<age>21</age>
</student>
<student id="2">
<name>herry</name>
<age>21</age>
</student>
<student id="3">
<name>andy</name>
<age>20</age>
</student>
<student id="4">
<name>lulu</name>
<age>21</age>
</student>
<student id="5">
<name>jerry</name>
<age>22</age>
</student>
</students>

javabean student.java

package test2.domain;

public class Student {
private String name;
private String id;
private String age;
public Student(){}
public String getName() {
return name;
}
public void setName(String name) {
if(name.matches("[a-zA-Z]+")){
this.name = name;
}else{
throw new RuntimeException("姓名");
}
}
public String getId() {
return id;
}
public void setId(String id) {
if(id.matches("[0-9]+")){
this.id = id;
}else{
throw new RuntimeException("编号");
}
}
public String getAge() {
return age;
}
public void setAge(String age) {
if(age.matches("[1-9][0-9]")){
this.age = age;
}else{
throw new RuntimeException("年龄");
}
};
}

文本文件id.txt