基于XML数据库的学生信息管理系统的设计与实现

本项目是在学习之余写的，主要用来练习MVC+DAO的分层设计思想，项目基于一个简单的XML学生数据库，使用XML作为数据库的原因是其十分的小巧与方便，使用dom4j即可进行方便的解析。因为这段时间课程一直比较密集，在Java相关内容的学习上比较滞后。希望用这个小项目来练一练久矣不写代码的手，也作为研一一个月来的学习小结吧。不废话了，具体内容如下：

项目说明：

本项目提供简单的用户界面（命令行），实现对XML数据库中学生数据的增删改查操作。项目要求使用分层设计思想，为什么要分层？分层可以将不同的代码块分离出来，避免不同功能的代码耦合，为程序扩展和维护提供方便。使用分层，也可以简单化一个系统的设计过程。

DB: students.xml
- Entity: Student 类 (packet: cn.myseu.test.stuMana.entity)
- Dao: StudentDao 类，完成具体的增删改查操作 (packet: cn.myseu.test.stuMana.dao)
- UI: StudentUI 类，实现用户输入操作  (packet: cn.myseu.test.stuMana.ui)
- SMS 类，提供主函数和用户界面  ( packet: cn.myseu.test.stuMana )

数据库如下：student.xml

<?xml version="1.0" encoding="UTF-8"?><students>   <student id="133122">     <name>well</name>      <age>22</age>   </student> </students>

设计Student类完成对数据库中数据的封装

package cn.myseu.test.stuMana.entity;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;}}

设计StudentDao类完成对XML数据库的增删改查操作（这里将公操作进行了抽取，分布为getDocument()和write2xml()）

package cn.myseu.test.stuMana.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.Element;import org.dom4j.io.OutputFormat;import org.dom4j.io.SAXReader;import org.dom4j.io.XMLWriter;import cn.myseu.test.stuMana.entity.Student;public class StudentDao {/** * Add a new student to the database * @param s * @return * @throws Exception  */public boolean create(Student s) throws Exception{boolean flag = false;if(s!=null){Document doc = getDocument();Element root = doc.getRootElement();Element newElement = root.addElement("student");newElement.addAttribute("id", s.getId());newElement.addElement("name").setText(s.getName());newElement.addElement("age").setText(s.getAge());write2xml(doc);flag = true;}return flag;}/** * delete a student from the xml-database * @param id  the student_id you want to delete * @return * @throws Exception */public boolean delete(String id) throws Exception{boolean flag = false;Document doc = getDocument();String xpath = "//student[@id='"+id+"']";Element element = (Element) doc.selectSingleNode(xpath);if(element!=null){element.getParent().remove(element);write2xml(doc);flag = true;}elseSystem.out.println("ID is not existed!");return flag;}/** * search the information of a specified student * @param id * @throws Exception */public void check(String id) throws Exception{Document doc = getDocument();String xpath = "//student[@id='"+id+"']";Element element = (Element) doc.selectSingleNode(xpath);if(element!=null){System.out.println("stu_id:"+element.attributeValue("id"));System.out.println("stu_name:"+element.elementText("name"));System.out.println("stu_age:"+element.elementText("age"));}elseSystem.out.println("ID is not existed!");}/** * update a specified student * @param s * @return * @throws Exception */public boolean update(Student s) throws Exception{boolean flag = false;Document doc = getDocument();String xpath = "//student[@id='"+s.getId()+"']";Element element = (Element) doc.selectSingleNode(xpath);if(element!=null){element.element("name").setText(s.getName());element.element("age").setText(s.getAge());write2xml(doc);flag = true;}elseSystem.out.println("ID is not existed!");return flag;}/* * the public function * getDocument() & write2xml */private void write2xml(Document doc) throws FileNotFoundException,UnsupportedEncodingException, IOException {OutputStream os = new FileOutputStream(new File("src/cn/myseu/test/stuMana/db/students.xml"));OutputFormat format = OutputFormat.createPrettyPrint();XMLWriter xw = new XMLWriter(os,format);xw.write(doc);xw.close();}private Document getDocument() throws DocumentException {SAXReader sr = new SAXReader();Document doc = sr.read(new File("src/cn/myseu/test/stuMana/db/students.xml"));return doc;}}

设计StudentUI类，完成系统功能：

package cn.myseu.test.stuMana.ui;import java.util.Scanner;import cn.myseu.test.stuMana.dao.StudentDao;import cn.myseu.test.stuMana.entity.Student;public class StudentUI {public void create() throws Exception{Scanner scanner = new Scanner(System.in);System.out.println("Input stu_id:");String id = scanner.nextLine();System.out.println("Input stu_name:");String name = scanner.nextLine();System.out.println("Input stu_age:");String age = scanner.nextLine();Student s = new Student();s.setId(id);s.setName(name);s.setAge(age);StudentDao stuDao = new StudentDao();boolean flag = stuDao.create(s);if(flag)System.out.println("Your create operation is successful!");elseSystem.out.println("Your create operation is failed!");}public void delete() throws Exception{Scanner scanner = new Scanner(System.in);System.out.println("Input the stu_id of the student who you want to delete:");String id = scanner.nextLine();StudentDao stuDao = new StudentDao();boolean flag = stuDao.delete(id);if(flag)System.out.println("Your delete operation is successful!");elseSystem.out.println("Your delete operation is failed!");}public void check() throws Exception{Scanner scanner = new Scanner(System.in);System.out.println("Input the stu_id of the student who you want to get:");String id = scanner.nextLine();StudentDao stuDao = new StudentDao();stuDao.check(id);}public void update() throws Exception{Scanner scanner = new Scanner(System.in);System.out.println("Input the stu_id of the student who you want to update:");String id = scanner.nextLine();System.out.println("The new name:");String name = scanner.nextLine();System.out.println("The new age:");String age = scanner.nextLine();Student s = new Student();s.setId(id);s.setAge(age);s.setName(name);StudentDao stuDao = new StudentDao();boolean flag = stuDao.update(s);if(flag)System.out.println("Your delete operation is successful!");elseSystem.out.println("Your delete operation is failed!");}}

设计SMS类，提供系统菜单和用户输入输出：

package cn.myseu.test.stuMana;import java.util.Scanner;import cn.myseu.test.stuMana.ui.StudentUI;public class SMS {public static void main(String[] args) throws Exception {System.out.println("========================================");System.out.println("====== Student Management System =======");System.out.println("====== Version 1.0 Author:Well   =======");System.out.println("========================================");System.out.println("1.create a new student");System.out.println("2.delete a student from the system");System.out.println("3.search information of a student");System.out.println("4.update information of a student");System.out.println("========================================");System.out.println("Please input your operation number:");Scanner scanner = new Scanner(System.in);StudentUI sui = new StudentUI();int num = Integer.parseInt(scanner.nextLine());switch(num){case 1:sui.create();break;case 2:sui.delete();break;case 3:sui.check();break;case 4:sui.update();break;default:System.out.println("You should input form [1-4]");;break;}}}

最后，简单而丑陋的系统运行界面如下：

最后，这个简单丑陋的系统仅仅是练习和复习相关的知识所用。但我认为也是一个非常简单的分层设计思想的很好的体现。系统简单容易上手。大概用了3个小时左右设计完成。