agentdaofromfile.java

一个很详细的航空售票系统开发的例子

package com.tarena.abs.dao;

import java.util.*;
import java.io.*;

import com.tarena.abs.model.Agent;

public class AgentDAOFromFile implements AgentDAO {
	private File file;
	
	public AgentDAOFromFile(File file){
		this.file=file;
		FileOutputStream fos=null;
		ObjectOutputStream oos=null;
		FileInputStream fis=null;
		ObjectInputStream ois=null;
		Object obj=null;
		
		try {//试着读取文件中的对象
			fis=new FileInputStream(file);
			ois=new ObjectInputStream(fis);
			obj=ois.readObject();
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			if(ois!=null)try{ois.close();}catch(IOException e){}
			if(fis!=null)try{fis.close();}catch(IOException e){}
		}
		
		//如果读到的对象为null，或者不是HashSet
		if(obj==null || !(obj instanceof HashSet)){
			try {//就向文件中写入一个空的HashSet
				fos=new FileOutputStream(file);
				oos=new ObjectOutputStream(fos);
				oos.writeObject(new HashSet());
				oos.flush();
			} catch (Exception e) {
				e.printStackTrace();
			}finally{
				if(oos!=null)try{oos.close();}catch(IOException e){}
				if(fos!=null)try{fos.close();}catch(IOException e){}
			}
		}
	}
	
	public Agent getAgent(String name, String passwd) {
		FileInputStream fis=null;
		ObjectInputStream ois=null;
		HashSet hs=null;
		try {
			fis=new FileInputStream(file);
			ois=new ObjectInputStream(fis);
			hs=(HashSet)ois.readObject();
		} catch (Exception e) {
			e.printStackTrace();
		}
		Iterator it=hs.iterator();
		while(it.hasNext()){
			Agent a=(Agent)it.next();
			if(a.getName().equals(name) && a.getPasswd().equals(passwd)){
				return a;
			}
		}
		return null;
	}

	public boolean addAgent(Agent user) {
		// TODO Auto-generated method stub
		FileInputStream fis=null;
		ObjectInputStream ois=null;
		HashSet hs=null;
		try {
			fis=new FileInputStream(file);
			ois=new ObjectInputStream(fis);
			hs=(HashSet)ois.readObject();
		} catch (Exception e) {
			e.printStackTrace();
		}
		if(hs!=null){
			Iterator it=hs.iterator();
			while(it.hasNext()){
				Agent a=(Agent)it.next();
				if(user.getName().equals(a.getName()))
					return false;
			}
		}
		hs.add(user);
		try {
			FileOutputStream fos=new FileOutputStream(file);
			ObjectOutputStream oos=new ObjectOutputStream(fos);
			oos.writeObject(hs);
			oos.flush();
		} catch (FileNotFoundException e) {
			// TODO 自动生成 catch 块
			e.printStackTrace();
		} catch (IOException e) {
			// TODO 自动生成 catch 块
			e.printStackTrace();
		}
		
		return true;
	}

	public boolean removeAgent(String name) {
		// TODO Auto-generated method stu
		FileInputStream fis=null;
		ObjectInputStream ois=null;
		HashSet hs=null;
		try {
			fis=new FileInputStream(file);
			ois=new ObjectInputStream(fis);
			hs=(HashSet)ois.readObject();
		} catch (Exception e) {
			return false;
		}
	
			Iterator it=hs.iterator();
			while(it.hasNext()){
				Agent a=(Agent)it.next();
				if(a.getName().equals(name)){
					hs.remove(a);
					try {
						FileOutputStream fos=new FileOutputStream(file);
						ObjectOutputStream oos=new ObjectOutputStream(fos);
						oos.writeObject(hs);
						oos.flush();
					} catch (FileNotFoundException e) {
						// TODO 自动生成 catch 块
						e.printStackTrace();
					} catch (IOException e) {
						// TODO 自动生成 catch 块
						e.printStackTrace();
					}
					return true;
				}
			}
		return false;
	}

	public Agent updateScore(String name, int n) {
		FileInputStream fis = null;
		ObjectInputStream ois = null;
		HashSet hs = new HashSet();
		try {
			fis = new FileInputStream(file);
			ois = new ObjectInputStream(fis);
			hs = (HashSet)ois.readObject();
			ois.close();
			fis.close();
			
		} catch (Exception e) {
			return null;
		}
		Iterator it = hs.iterator();
		while(it.hasNext()){
			Agent a = (Agent)it.next();
			if(a.getName().equals(name)){
				a.setScore(a.getScore()+n);
				try {
					ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file));
					oos.writeObject(hs);
					oos.flush();
					oos.close();
				}catch (IOException e) {
					return null;
				}
				return a;
			}
		}
		return null;
	}

	public boolean modifyPassword(String name, String oldPassword,
			String newPassword) {
		// TODO Auto-generated method stub
		FileInputStream fis=null;
		ObjectInputStream ois=null;
		HashSet hs=null;
		try {
			fis=new FileInputStream(file);
			ois=new ObjectInputStream(fis);
			hs=(HashSet)ois.readObject();
		} catch (Exception e) {
			e.printStackTrace();
		}
		if(hs!=null){
			Iterator it=hs.iterator();
			while(it.hasNext()){
				Agent a=(Agent)it.next();
				if(a.getName().equals(name)){
					a.setPasswd(newPassword);
					try {
						FileOutputStream fos=new FileOutputStream(file);
						ObjectOutputStream oos=new ObjectOutputStream(fos);
						oos.writeObject(hs);
					}catch(Exception e){
						return false;
					}
					return true;
				}
			}
		}
		return false;
	}

	public Set getAllAgent() {
		// TODO Auto-generated method stub
		FileInputStream fis=null;
		ObjectInputStream ois=null;
		HashSet hs=null;
		try {
			fis=new FileInputStream(file);
			ois=new ObjectInputStream(fis);
			hs=(HashSet)ois.readObject();
		} catch (Exception e) {
			return null;
		}
		return hs;
	}


}