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;
		}else
			System.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"));
		}else
			System.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;
		}
		else
			System.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!");
		else
			System.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!");
		else
			System.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!");
		else
			System.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。