Java基于对象流实现银行系统

系统特点：

• 数据持久化到文件中，系统启动后，加载文件中数据到集合中，相当于做了一个缓存。
• 文件读写使用的是对象流（ObjectInputStream和ObjectOutputStream），用户是看不懂那些文件的，一定程度上保证了密码和余额的安全性。
• 采用了MVC分层设计思想，虽然没有C控制层和V视图层，但是有完备的M模型层，数据处理Service，数据读写Dao，数据存储POJO（每一层只负责处理自己的事情，层次内部的改动不会影响其他层次）。
• 虽然有些细节问题由于时间关系没有处理好，比如没有处理输入类型不匹配的异常，但是绝大多数功能都合理得实现了。

全部代码

pojo：

public class User implements Serializable {
    private static final long serialVersionUID = -7019656536540026883L;
    private String username;//用户名
    private String password;//密码
    private Double balance;//余额

    public User(String username, String password, Double balance) {
        this.username = username;
        this.password = password;
        this.balance = balance;
    }

    public User() {
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Double getBalance() {
        return balance;
    }

    public void setBalance(Double balance) {
        this.balance = balance;
    }
    public String toString(){
        StringBuilder builder = new StringBuilder("{");
        builder.append(this.username).append(",").append(this.password).append(",").append(this.balance).append("}");
        return builder.toString();
    }

dao层：

public class ATMDao {
    private String userFilePath = "src\\userMsg.txt";//相对路径
    private HashMap<String, User>  userMsg;
    {
        userMsg = this.loadFile();//读取文件信息
    }
    public HashMap<String, User> getUserMsg() {
        return userMsg;
    }
    //查询用户
    public User selectUser(String username){
        return userMsg.get(username);
    }
    //更新用户信息
    public void updateUser(User user){
        this.userMsg.replace(user.getUsername(),user);
        this.updateFile(userMsg);
    }
    //增加用户
    public void addUser(User user){
        this.userMsg.put(user.getUsername(),user);
        this.updateFile(userMsg);
    }
    //删除用户
    public void deleteUser(User user){
        this.userMsg.remove(user.getUsername());
        this.updateFile(userMsg);
    }

    //只在初始化时时调用一次
/*    public void initFile(){
        User user1 = new User("张三","123",800.0);
        User user2 = new User("李四","666",70.0);
        User user3 = new User("王五","888",555.0);
        userMsg.put(user1.getUsername(),user1);
        userMsg.put(user2.getUsername(),user2);
        userMsg.put(user3.getUsername(),user3);
        this.updateFile(userMsg);
    }*/
    private HashMap<String, User> loadFile(){
        File file = new File(userFilePath);
        FileInputStream fis = null;
        ObjectInputStream ois = null;
        HashMap<String, User> box = null;
        try {
            fis = new FileInputStream(file);
            ois = new ObjectInputStream(fis);
            try {
                box = (HashMap<String, User>)ois.readObject();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if(fis!=null)
                    fis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                if(ois!=null)
                    ois.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return box;
    }
    private void updateFile(HashMap<String,User> userMsg){
        File file = new File(userFilePath);
        FileOutputStream fos = null;
        ObjectOutputStream oos = null;
        try {
            fos = new FileOutputStream(file);
            oos = new ObjectOutputStream(fos);
            oos.writeObject(userMsg);
            oos.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if(fos!=null)
                    fos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                if(oos!=null)
                    oos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

service层：

public class ATMService {
    ATMDao dao = new ATMDao();
    public boolean login(String username,String password){
        User user = dao.selectUser(username);
        if (user!=null && user.getPassword().equals(password))
            return true;
        else
            return false;
    }
    //查询余额
    public Double queryBalance(String name){
        User user = dao.selectUser(name);
        return user.getBalance();
    }
    //存款
    public void deposit(String name,Double account){
        User user = dao.selectUser(name);
        user.setBalance(user.getBalance()+account);
        dao.updateUser(user);
    }
    //取款
    public void withdrawal(String name,Double account){
        User user = dao.selectUser(name);
        if (user.getBalance()>=account) {
            user.setBalance(user.getBalance() - account);
            dao.updateUser(user);
        }else {
            System.err.println("对不起，"+user.getUsername()+"，您的余额不足");
        }
    }
    //转账
    public void transfer(String oldName,String newName,Double account){
        User oldUser = dao.selectUser(oldName);
        User newUser = dao.selectUser(newName);
        if (newUser!=null){
            if (oldUser.getBalance()>=account){
                oldUser.setBalance(oldUser.getBalance()-account);
                newUser.setBalance(newUser.getBalance()+account);
                dao.updateUser(oldUser);
                dao.updateUser(newUser);
            }else {
                System.err.println("对不起，"+oldUser.getUsername()+"，您的余额不足");
            }
        }else {
            System.err.println("对不起，您输入的账号不存在");
        }
    }
    //销户
    public void closeAccount(String name){
        User u = dao.selectUser(name);
        dao.deleteUser(u);
    }
    //注册
    public void register(String name,String password){
        User user = dao.selectUser(name);
        if (user!=null){
            System.err.println("对不起，您输入的账号已存在");
        }else {
            user = new User(name,password,0.0);
            dao.addUser(user);
        }
    }
}

测试：

public class Test {
    public static void main(String[] args) {
        ATMService service = new ATMService();
        Scanner input = new Scanner(System.in);
        System.out.println("欢迎您使用银行自助服务系统\n请输入您的账号:");
        String username = input.nextLine();
        System.out.println("请输入您的密码：");
        String password = input.nextLine();
        if (service.login(username,password)){
            System.out.println("登录成功!");
            while(true) {
                System.out.println("请选择您的操作：\n0.注册\n1.查询余额\n2.存款\n3.取款\n4.转账\n5.销户\n6.退出");
                String option = input.nextLine();
                switch (option) {
                    case "0":
                        System.out.println("请输入您的用户名：");
                        String newname = input.nextLine();
                        System.out.println("请输入您的密码：");
                        String newPass = input.nextLine();
                        service.register(newname, newPass);
                        System.out.println("恭喜您，注册成功！，您的用户名为" + newname);
                        break;
                    case "1":
                        Double balance = service.queryBalance(username);
                        System.out.println("您的余额为" + balance);
                        break;
                    case "2":
                        System.out.println("请输入存款金额：");
                        double amount = input.nextDouble();
                        input.nextLine();
                        service.deposit(username, amount);
                        System.out.println("恭喜您，存款成功");
                        break;
                    case "3":
                        System.out.println("请输入取款金额：");
                        double d = input.nextDouble();
                        input.nextLine();
                        service.withdrawal(username, d);
                        System.out.println("恭喜您，取款成功");
                        break;
                    case "4":
                        System.out.println("请输入对方账户：");
                        String anothername = input.nextLine();
                        System.out.println("请输入转账金额：");
                        double t = input.nextDouble();
                        input.nextLine();
                        service.transfer(username, anothername, t);
                        System.out.println("恭喜您，转账成功");
                        break;
                    case "5":
                        service.closeAccount(username);
                        System.out.println("销户成功");
                        break;
                    case "6":
                        System.exit(0);
                }
            }
        }else {
            System.err.println("用户名或密码错误");
        }
        //dao.initFile();
        /*HashMap<String, User> userMsg = dao.getUserMsg();
        Iterator<String> iterator = userMsg.keySet().iterator();
        while (iterator.hasNext()){
            String username = iterator.next();
            User user = userMsg.get(username);
            System.out.println(user);
        }*/
    }
}

部分测试截图