使用xml实现增删改查

package cn.jxau.utils;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
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 XmlUtils {
	
	private static String filepath;
	static{
		filepath = XmlUtils.class.getClassLoader().getResource("users.xml").getPath();
	}

	public static Document getDocument() throws Exception{
		SAXReader reader = new SAXReader();
        Document document = reader.read(new File(filepath));
        return document;
	}
	
	public static void write2Xml(Document document) throws IOException{
		
		OutputFormat format = OutputFormat.createPrettyPrint();
		format.setEncoding("UTF-8");
		XMLWriter writer = new XMLWriter(new FileOutputStream(filepath), format );
        writer.write( document );
        writer.close();
	}
	
}

package cn.jxau.dao.impl;

import java.text.SimpleDateFormat;

import org.dom4j.Document;
import org.dom4j.Element;

import cn.jxau.dao.UserDao;
import cn.jxau.domain.User;
import cn.jxau.exception.DaoException;
import cn.jxau.utils.XmlUtils;

public class UserDaoXmlImpl implements UserDao {

	public void add(User user){
		try{
			Document document = XmlUtils.getDocument();
			Element root = document.getRootElement();
			
			Element user_tag = root.addElement("user");
			user_tag.setAttributeValue("id", user.getId());
			user_tag.setAttributeValue("username", user.getUsername());
			user_tag.setAttributeValue("password", user.getPassword());
			user_tag.setAttributeValue("email", user.getEmail());
			user_tag.setAttributeValue("birthday", user.getBirthday()==null?"":user.getBirthday().toLocaleString());
			user_tag.setAttributeValue("nickname", user.getNickname());
		
			XmlUtils.write2Xml(document);
		}catch (Exception e) {
			throw new DaoException(e);
		}
	}
	
	public User find(String username,String password){
		try{
			Document document = XmlUtils.getDocument();
			Element e = (Element) document.selectSingleNode("//user[@username='"+username+"' and @password='"+password+"']");
			if(e==null){
				return null;
			}
			User user = new User();
			String date = e.attributeValue("birthday");  //  ""   1980-09-09
			if(date==null || date.equals("")){
				user.setBirthday(null);
			}else{
				SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
				user.setBirthday(df.parse(date));
			}
			
			user.setEmail(e.attributeValue("email"));
			user.setId(e.attributeValue("id"));
			user.setNickname(e.attributeValue("nickname"));
			user.setPassword(e.attributeValue("password"));
			user.setUsername(e.attributeValue("username"));
			
			return user;
		
		}catch (Exception e) {
			throw new DaoException(e);
		}
	}
	
	//查找注册的用户是否在数据库中存在
	public boolean find(String username){
		
		try{
			Document document = XmlUtils.getDocument();
			Element e = (Element) document.selectSingleNode("//user[@username='"+username+"']");
			if(e==null){
				return false;
			}
			return true;
		}catch (Exception e) {
			throw new DaoException(e);
		}
	}
}