一个基础XML作为数据库的学生信息管理程序

对于那些比如学生信息的纯文本数据的存取，现在比较流行的是将他进行XML存放，而不是安装数据库去存放这些文字，这也算是目前XML的一个比较好的用途，本文在J***A自带的XML解析器的基础上，实现了控制台输入命令对XML文档进行增删改查的功能，而且引入了编译异常与运行异常和异常作为返回值的内容，比较耐看，下面将代码分模块贴出。

一。Java Bean 实现对学生信息的面向对象封装

package com.bird.domain;

public class Student {
	private String idcard;
	private String examid;
	private String name;
	private String location;
	private double grade;
	
	
	public 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;
	}
}

二、DAO也就是数据库访问层代码，（主要部分）

package com.bird.dao;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import com.bid.utils.XmlUtils;
import com.bird.Exception.StudentNotExitException;
import com.bird.domain.Student;

public class StudentDao {
	public void add(Student s){
		try {
			Document document = XmlUtils.getDocument();
			
			//创建出封装学生信息的标签
			Element student_tag = document.createElement("student");
			
			//设置属性
			student_tag.setAttribute("idcard", s.getIdcard());
			student_tag.setAttribute("examid", s.getExamid());
			
			//创建用于封装学生姓名、地址和成绩的标签
			Element name = document.createElement("name");
			Element location = document.createElement("location");
			Element grade = document.createElement("grade");
			
			//设置内容
			name.setTextContent(s.getName());
			location.setTextContent(s.getLocation());
			grade.setTextContent(String.valueOf(s.getGrade()));
			
			//设置他们的关系
			student_tag.appendChild(name);
			student_tag.appendChild(location);
			student_tag.appendChild(grade);
			
			//把得到的根节点挂到文档上
			document.getElementsByTagName("exam").item(0).appendChild(student_tag);
			
			//更新内存
			XmlUtils.write2Xml(document);
		} catch (Exception e) {
			throw new RuntimeException(e);//将编译异常转换成运行时异常，方便上层想处理就处理不像处理拉到
		}
	}
	
	public Student find(String examid){
		try {
			Document document = XmlUtils.getDocument();
			NodeList list = document.getElementsByTagName("student");//获得所有的student节点进行判断
			for(int i = 0; i < list.getLength(); i++){
				Element student_tag = (Element) list.item(i);
				if(student_tag.getAttribute("examid").equals(examid)){
					//找到这个学生的信息
					Student s = new Student();
					s.setExamid(examid);
					s.setIdcard(student_tag.getAttribute("idcard"));
					s.setName(student_tag.getElementsByTagName("name").item(0).getTextContent());
					s.setLocation(student_tag.getElementsByTagName("location").item(0).getTextContent());
					s.setGrade(Double.parseDouble(student_tag.getElementsByTagName("grade").item(0).getTextContent()));
					return s;
				}
			}
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
		
		return null;
	}
	
	public void delete(String name) throws StudentNotExitException{
		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 StudentNotExitException(name + "不存在 ！！");//编译时异常，要抛出，说明不存在，把异常当作返回值
		}catch(StudentNotExitException e){
			throw e;
		}catch (Exception e) {
			throw new RuntimeException(e);
		}
		
	}
}

三。其中DAO访问层经常使用的代码块进行了封装，弄成打包了一个工具类

package com.bid.utils;

import java.io.FileOutputStream;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;

public class XmlUtils {// 工具类所有方法都得时静态的
	private static String filename = "d://exam.xml";

	public static Document getDocument() throws Exception {// 获得XML的Document
		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
		DocumentBuilder builder = factory.newDocumentBuilder();
		return builder.parse(filename);
	}

	public static void write2Xml(Document doc) throws Exception {// 将更改后的XML更新到硬盘
		TransformerFactory factory = TransformerFactory.newInstance();
		Transformer tf = factory.newTransformer();
		tf.transform(new DOMSource(doc), new StreamResult(new FileOutputStream(
				filename)));
	}
}

四。需要删除信息不存在的异常，自己编写，作为返回值

package com.bird.Exception;

public class StudentNotExitException extends Exception {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	public StudentNotExitException() {
		// TODO Auto-generated constructor stub
	}

	public StudentNotExitException(String message) {
		super(message);
		// TODO Auto-generated constructor stub
	}

	public StudentNotExitException(Throwable cause) {
		super(cause);
		// TODO Auto-generated constructor stub
	}

	public StudentNotExitException(String message, Throwable cause) {
		super(message, cause);
		// TODO Auto-generated constructor stub
	}

}

五。DAO测试代码

package com.bird.test;

import com.bird.Exception.StudentNotExitException;
import com.bird.dao.StudentDao;
import com.bird.domain.Student;

/**
 * @测试类
 * @author Bird
 * 
 */
public class DaoTest {
	public static void main(String[] args) throws StudentNotExitException {
		StudentDao dao = new StudentDao();
		@SuppressWarnings("unused")
		Student s = new Student();
		/*
		 * s.setExamid("123"); s.setGrade(99); s.setIdcard("31234");
		 * s.setLocation("上海"); s.setName("鸟"); dao.add(s);
		 */

		// System.out.println(dao.find("222").getLocation());

		dao.delete("张三");

	}
}

六。用户使用UI层

package com.bird.ui;

import java.io.BufferedReader;
import java.io.InputStreamReader;

import com.bird.Exception.StudentNotExitException;
import com.bird.dao.StudentDao;
import com.bird.domain.Student;

/**
 * @客户使用程序
 * @author Bird
 *
 */
public class Main {
	public static void main(String [] args){
		try{
		System.out.println("添加学生（a）    删除学生(b)   查找学生(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.equals("a")){
			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***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 s = new Student();
			s.setName(name);
			s.setExamid(examid);
			s.setGrade(Double.parseDouble(grade));
			s.setIdcard(idcard);
			s.setLocation(location);
			
			StudentDao dao = new StudentDao();
			dao.add(s);
			
			System.out.println("添加成功");
		}else if(type.equals("b")){
			System.out.print("请输入要删除的学生的姓名");
			String namen = br.readLine();
			try{
			StudentDao dao = new StudentDao();
			dao.delete(namen);
			System.out.println("删除成功");
			}catch(StudentNotExitException e){
				System.out.println("您要删除的学生不存在");
			}
		}else if(type.equals("c")){
			System.out.print("请输入您要查询的学生准考证号");
			String num = br.readLine();
			StudentDao dao = new StudentDao();
			System.out.println("成绩为" + dao.find(num).getGrade());
		}else{
			System.out.println("对不起，不支持您的操作！！");
		}
		}catch(Exception e){
			e.printStackTrace();
			System.out.println("对不起，俺出错了！！！");
		}
	}
}

七。总结

麻雀虽小五脏俱全，这个小系统的模块划分和异常处理可以作为

以后大程序的典范