案例需求
涉及知识点
面向对象，接口，Java序列化，HashMap，IO流
欢迎界面
public class BootStrap {
public static void main(String[] args) {
System.out.println("欢迎来到自动售货系统，请选择：");
FrontMenu.showFirstLevelMeun();
}
}
一级目录
public class FrontMenu {
public static void showFirstLevelMeun() {
UserService userService = new UserServiceImp();
System.out.println("1、注册 2、登录");
Scanner sc = new Scanner(System.in);
String select = sc.nextLine();
//注册
if(select.equals("1")) {
System.out.println("请输入用户名：");
String username = sc.nextLine();
System.out.println("请输入密码：");
String password = sc.nextLine();
System.out.println("请再次输入密码：");
String password2 = sc.nextLine();
if(password.equals(password2)) {
boolean isExists = userService.isExists(username);
if(isExists) {
System.out.println("此用户名已存在");
showFirstLevelMeun();
}else {
System.out.println("请输入地址：");
String address = sc.nextLine();
userService.regist(username,password,address);
}
}else {
System.out.println("您输入的密码不一致");
showFirstLevelMeun();
}
}else if(select.equals("2")) {
//登录
System.out.println("请输入用户名：");
String username = sc.nextLine();
System.out.println("请输入密码：");
String password = sc.nextLine();
boolean success = userService.login(username,password);
if(success) {
System.out.println("登录成功");
}else {
System.out.println("用户名或者密码错误");
showFirstLevelMeun();
}
}else {
System.out.println("您输入的选项不正确");
showFirstLevelMeun();
}
}
}
登录注册功能交互
public interface UserService {
/*
* 判断用户名是否已经存在
*/
boolean isExists(String username);
/*
* 注册一个用户
*/
void regist(String username, String password,String address);
/*
* 登录
*/
boolean login(String username, String password); }
实现接口中的具体方法
public class UserServiceImp implements UserService{
UserDao userdao = new UserDaoImp();
/*
* 判断用户名是否存在
*/
@Override
public boolean isExists(String username) {
HashMap<String,User> userMap = userdao.loadUserData();
return userMap.containsKey(username);
}
/**
* 注册
*/
@Override
public void regist(String username, String password,String address) {
User user = new User();
user.setUsername(username);
user.setPassword(password);
user.setAddress(address);
//调用dao将user数据添加到hashmap中
HashMap<String,User> userMap = userdao.loadUserData();
//将新用户对象添加到userMap中
userMap.put(user.getUsername(), user);
//调用dao将添加后usermap保存到数据文件中
userdao.saveUserData(userMap);
System.out.println("注册成功");
FrontMenu.showFirstLevelMeun();
}
/*
* 登录
*/
@Override
public boolean login(String username, String password) {
//调用dao将user数据添加到hashmap中
HashMap<String,User> userMap = userdao.loadUserData();
if(userMap.containsKey(username)) {
User user = userMap.get(username);
if(user.getPassword().equals(password)) {
return true;
}else {
return false;
}
}else {
return false;
}
}
}
程序中的用户数据与磁盘文件存储数据的接口
public interface UserDao {
/**
* 将数据文件中得数据读取到hashmap中
*/
HashMap<String, User> loadUserData();
/**
* 将hashmap中的数据保存到数据文件中
*/ void saveUserData(HashMap<String, User> userMap);
}
实现接口中的具体方法
public class UserDaoImp implements UserDao{ /**
* 将hashMap中的数据保存到用户数据文件中
*/
@Override
public HashMap<String, User> loadUserData() {
File file = new File("D:/user.data");
try {
if(!file.exists()) {
HashMap<String, User> userMap = new HashMap<String, User>();
ObjectOutputStream oos = new ObjectOutputStream(new
FileOutputStream(file));
oos.writeObject(userMap);
oos.close();
return userMap;
}
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
HashMap<String, User> userMap = (HashMap<String, User>)ois.readObject();
ois.close();
return userMap;
} catch (Exception e) {
System.out.println("文件里没有对象");
e.printStackTrace();
}
System.out.println(3);
return null;
}
/*
* 将hashMap中的数据保存文件中
*/
@Override public void saveUserData(HashMap<String, User> userMap) {
try {
ObjectOutputStream oos = new ObjectOutputStream(new
FileOutputStream("D:/user.data"));
oos.writeObject(userMap);
oos.flush();
oos.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
使用的user类
public class User implements Serializable{
private String username;
private String password;
private String address;
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 String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
注意事项
1.进行序列化的对象必须要实现Serializable接口
2.IO流的关流操作
3.HashMap的与序列化的相互转化细节，容易出现空指针异常
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