编写图书馆管理系统

源码https://github.com/Hu1Wence/Learn_Java/tree/master/BookManage

思路

要编写这个程序我们首相要清楚这个程序中有哪些对象,不考虑复杂情况，基本的对象有三个：

1. 书
2. 用户

那么我们就分别讨论这三个对象有哪些属性和有哪些动作。

1. 书籍 它会有书名，编号(id)， 作者， 类别， 价格， 是否被借 这些简单的属性
2. 用户包括：管理员和普通用户，管理员它会有姓名， 增加书籍， 删除书籍， 查找书籍， 打印所有书籍信息， 退出系统 这些简单属性。
   普通用户它会有姓名， 查找书籍， 借阅书籍， 归还书籍， 退出系统这些简单的属性。

我们把这三个对象分别放入三个包中，这样在分别完成这些对象中所需的动作(方法)。
我们书籍包中的代码：

package book;

public class Book {
    
    private String name;
    private String id;
    private String author;
    private String type;
    private int price;
    private boolean isBorrow;

    public Book(String name, String id, String author, String type, int price, boolean isBorrow) {
    
        this.name = name;
        this.id = id;
        this.author = author;
        this.type = type;
        this.price = price;
        this.isBorrow = isBorrow;
    }

    public String getId() {
    
        return id;
    }

    public boolean isBorrow() {
    
        return isBorrow;
    }

    public void setBorrow(boolean borrow) {
    
        isBorrow = borrow;
    }

    public String getName() {
    
        return name;
    }

    @Override
    public String toString() {
    
        return "Book{" +
                "name='" + name + '\'' +
                ", id='" + id + '\'' +
                ", author='" + author + '\'' +
                ", type='" + type + '\'' +
                ", price=" + price +
                ", isBorrow=" + isBorrow +
                '}';
    }
}

同时创建一个类似顺序表的书籍数组保存书籍。

package book;

public class BookList {
    
    private Book[] books = new Book[100];
    private int size;

    public BookList() {
    
        books[0] = new Book("金瓶梅",
                "001", "兰陵笑笑生","古典名著",
                100, false);
        books[1] = new Book("水浒传",
                "002", "施耐庵","古典名著",
                100, false);
        books[2] = new Book("西游记",
                "003", "吴承恩","古典名著",
                100, false);
        size = 3;
    }

    public int getSize() {
    
        return size;
    }

    public void setSize(int size) {
    
        this.size = size;
    }

    public Book getBook(int index) {
    
        return books[index];
    }

    public void setBooks(int index, Book book) {
    
        books[index] = book;
    }
}

我们将用所有的操作方法放入operation包中，所有的方法都用接口来实现，这样我们就避免了使用一大堆的 if else

接口：

package operation;

import book.BookList;

public interface IOperation {
    
    void work(BookList bookList);
}

增加新书籍：

package operation;

import book.Book;
import book.BookList;

import java.util.Scanner;

public class AddBookOperation implements IOperation{
    
    @Override
    public void work(BookList bookList) {
    
        System.out.println("新增一本书籍!");
        System.out.println("请输入新增书籍的书名: ");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.next();
        System.out.println("请输入新增书籍的id: ");
        String id = scanner.next();
        System.out.println("请输入新增书籍的作者: ");
        String author = scanner.next();
        System.out.println("请输入新增书籍的类型: ");
        String type = scanner.next();
        System.out.println("请输入新增书籍的价格: ");
        int price = scanner.nextInt();
        Book book = new Book(name, id, author, type, price, false);
        bookList.setBooks(bookList.getSize(), book);
        bookList.setSize(bookList.getSize() + 1);
    }
}

删除书籍：

package operation;

import book.Book;
import book.BookList;

import java.util.Scanner;

public class DeleteBookOperation implements IOperation {
    
    @Override
    public void work(BookList bookList) {
    
        System.out.println("删除书籍!");
        System.out.println("请输入您想要删除书籍的id: ");
        Scanner scanner = new Scanner(System.in);
        String id = scanner.next();
        int i = 0;
        for (; i < bookList.getSize(); i++) {
    
            Book book = bookList.getBook(i);
            if (book.getId().equals(id)) {
    
                break;
            }
        }
        if (i >= bookList.getSize()) {
    
            System.out.println("未找到要找的书籍!");
            return;
        }

        Book lastBook = bookList.getBook(bookList.getSize() - 1);
        bookList.setBooks(i, lastBook);
        bookList.setSize(bookList.getSize() - 1);
        System.out.println("删除成功!");
    }
}

查找书籍：

package operation;

import book.Book;
import book.BookList;

import java.util.Scanner;

public class FindOperation implements IOperation {
    
    @Override
    public void work(BookList bookList) {
    
        System.out.println("查找书籍!");
        System.out.println("请输入要查找书籍的书名: ");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.next();
        int count = 0;
        for (int i = 0; i < bookList.getSize(); i++) {
    
            Book book = bookList.getBook(i);
            if (book.getName().equals(name)) {
    
                System.out.println(book);
                count++;
            }
        }
        if (count == 0) {
    
            System.out.println("没找到此书籍!");
        } else {
    
            System.out.println("共找到 " + count + " 本相同书籍!");
        }
    }
}

借阅书籍：

package operation;

import book.Book;
import book.BookList;

import java.util.Scanner;

public class BorrowOperation implements IOperation {
    
    @Override
    public void work(BookList bookList) {
    
        System.out.println("借阅书籍!");
        System.out.println("请输入要借阅的书籍的id: ");
        Scanner scanner = new Scanner(System.in);
        String id = scanner.next();

        for (int i = 0; i < bookList.getSize(); i++) {
    
            Book book = bookList.getBook(i);
            if (!book.getId().equals(id)) {
    
                continue;
            }
            if (book.isBorrow()) {
    
                System.out.println("此书已经被借走了!");
                break;
            }
            book.setBorrow(true);
            System.out.println("借阅成功");
        }
    }
}

归还书籍：

package operation;

import book.Book;
import book.BookList;

import java.util.Scanner;

public class ReturnOperation implements IOperation {
    
    @Override
    public void work(BookList bookList) {
    
        System.out.println("归还书籍!");
        System.out.println("请输入要归还书籍的id: ");
        Scanner scanner = new Scanner(System.in);
        String id = scanner.next();
        int i = 0;
        for ( ; i < bookList.getSize(); i++) {
    
            Book book = bookList.getBook(i);
            if (!book.getId().equals(id)) {
    
                continue;
            }
            if (!book.isBorrow()) {
    
                System.out.println("这本书未借出去,归还失败!");
            }
            book.setBorrow(false);
        }
    }
}

打印所有书籍信息：

package operation;

import book.BookList;

public class PrintAllOperation implements IOperation {
    
    @Override
    public void work(BookList bookList) {
    
        for (int i = 0; i < bookList.getSize(); i++) {
    
            System.out.println(bookList.getBook(i));
        }
        System.out.println("共有 " + bookList.getSize() + " 本书籍");
    }
}

退出系统：

package operation;

import book.BookList;

public class ExitOperation implements  IOperation {
    
    @Override
    public void work(BookList bookList) {
    
        System.out.println("GoodBye!");
        System.exit(0);
    }
}

我们用户中先创建一个抽象的用户，再将不同用户通过实现这个抽象的用户来实现不同用户的操作权限。
我们用户包中的代码
抽象的用户代码：

package user;

import book.BookList;
import operation.IOperation;

abstract public class User {
    
    protected String name;

    protected IOperation[] operations;

    public User(String name) {
    
        this.name = name;
    }

    abstract public int menu();

    public void doOperation(int choice, BookList bookList) {
    
        operations[choice].work(bookList);
    }
}

管理员用户：

package user;

import book.BookList;
import operation.*;

import java.util.Scanner;

public class Admin extends User{
    
    public Admin(String name) {
    
        super(name);
        operations = new IOperation[] {
    
                new ExitOperation(),
                new AddBookOperation(),
                new DeleteBookOperation(),
                new FindOperation(),
                new PrintAllOperation(),
        };
    }

    @Override
    public int menu() {
    
        System.out.println("============");
        System.out.println("hello " + name);
        System.out.println("1. 增加书籍");
        System.out.println("2. 删除书籍");
        System.out.println("3. 查找书籍");
        System.out.println("4. 打印所有信息");
        System.out.println("0. 退出");
        System.out.println("============");
        System.out.println("请输入您的选择: ");
        Scanner scanner = new Scanner(System.in);
        int choice = scanner.nextInt();
        return choice;
    }
}

普通用户：

package user;

import operation.*;

import java.util.Scanner;

public class NormalUser extends  User {
    
    public NormalUser(String name) {
    
        super(name);
        operations = new IOperation[] {
    
                new ExitOperation(),
                new FindOperation(),
                new BorrowOperation(),
                new ReturnOperation(),
        };
    }

    @Override
    public int menu() {
    
        System.out.println("============");
        System.out.println("hello " + name);
        System.out.println("1. 查找图书");
        System.out.println("2. 借阅图书");
        System.out.println("3. 归还图书");
        System.out.println("0. 退出");
        System.out.println("============");
        System.out.println("请输入您的选择: ");
        Scanner scanner = new Scanner(System.in);
        int choice = scanner.nextInt();
        return choice;
    }
}

这样就完成了一个简单的图书馆管理系统。

这是测试类代码块

import book.BookList;
import user.Admin;
import user.NormalUser;
import user.User;

import java.util.Scanner;

public class Test {
    
    public static void main(String[] args) {
    
        BookList bookList = new BookList();
        User user = login();
        while (true) {
    
            int choice = user.menu();
            user.doOperation(choice, bookList);
        }
    }

    public static User login() {
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("欢迎来到图书管理系统!");
        System.out.println("请输入您的姓名: ");
        String name = scanner.next();
        System.out.println("请输入您的用户选项: 1 -> 管理员  2 -> 普通用户");
        int role = scanner.nextInt();
        if (role == 1) {
    
            return new Admin(name);
        } else {
    
            return new NormalUser(name);
        }
    }


}

---

新增登录、注册模块
创建dao包

我们的用户User类，包含用户名， 密码

package dao;

public class User {
    
    String username;
    String password;

    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;
    }
}

UserDao包含登录和注册

package dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDao {
    


    //注册
    public void login(User user) {
    
        Connection connection = DBUtil.getConnection();
        PreparedStatement statement = null;
        String sql = "insert into user values(?, ?)";

        try {
    
            statement = connection.prepareStatement(sql);
            statement.setString(1, user.getUsername());
            statement.setString(2, user.getPassword());
            int ret = statement.executeUpdate();
            if (ret != 1) {
    
                System.out.println("当前数据库执行插入数据出错");
                return;
            }
        } catch (SQLException throwables) {
    
            throwables.printStackTrace();
        } finally {
    
            DBUtil.close(connection, statement, null);
        }
    }

    //登录
    public int enter(String username, String password) {
    
        List<String> list = new ArrayList<>();
        Connection connection = DBUtil.getConnection();
        String sql = "select username, password from user where username = ?";
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        int ret = 0;
        try {
    
            statement = connection.prepareStatement(sql);
            statement.setString(1, username);
            while (resultSet.next()) {
    
                String pass = resultSet.getString(password);
                list.add(pass);
            }
            if (list.contains(password)) {
    
                ret = 1;
            }
        } catch (SQLException throwables) {
    
            throwables.printStackTrace();
        } finally {
    
            DBUtil.close(connection, statement, resultSet);
        }
        return ret;
    }
}

DBUtil实现连接数据库

package dao;

import java.sql.*;

public class DBUtil {
    
    private static final String URL = "jdbc:mysql://localhost:3306/java_github_crawler";

    private static final String USERNAME = "root";

    private static final String PASSWORD = "123456";

    private static Connection conn = null;
    static{
    
        try {
    
            //1.加载驱动程序
            Class.forName("com.mysql.jdbc.Driver");
            //2. 获得数据库连接
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        } catch (ClassNotFoundException e) {
    
            e.printStackTrace();
        } catch (SQLException e) {
    
            e.printStackTrace();
        }
    }

    public static Connection getConnection(){
    
        return conn;
    }


    //释放资源
    public static void close(Connection connection, Statement statement, ResultSet resultSet) {
    
        try {
    
            if (resultSet != null) {
    
                resultSet.close();
            }
            if (statement != null) {
    
                statement.close();
            }
            if (connection != null) {
    
                connection.close();
            }
        } catch (Exception e) {
    
            throw new RuntimeException("释放数据库资源失败", e);
        }
    }

}

新的测试类：

import book.BookList;
import dao.UserDao;
import user.Admin;
import user.NormalUser;
import user.User;

import java.util.Scanner;

public class Test {
    
    public static void main(String[] args) {
    
        BookList bookList = new BookList();
        User user = login();
        if (user == null) {
    
            return;
        }
        while (true) {
    
            int choice = user.menu();
            user.doOperation(choice, bookList);
        }
    }

    public static User login() {
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("欢迎来到图书管理系统!");
        dao.User user = new dao.User();
        System.out.println("请输入您的用户选项: 1 -> 注册  2 -> 登录");
        int role = scanner.nextInt();
        UserDao userDao = new UserDao();
        boolean isEnter = false;
        if (role == 1) {
    
            System.out.println("请输入用户名: ");
            user.setUsername(scanner.nextLine());
            System.out.println("请输入密码: ");
            user.setPassword(scanner.nextLine());
            userDao.login(user);
        } else {
    
            for (int i = 3; i >= 0; i--) {
    
                System.out.println("请输入用户名: ");
                String username = scanner.nextLine();
                System.out.println("请输入密码: ");
                String password = scanner.nextLine();
                int ret = userDao.enter(username, password);
                if (ret != 1) {
    
                    System.out.println("登录失败,您还有 " + i + "次机会");
                } else {
    
                    System.out.println("登录成功");
                    isEnter = true;
                    break;
                }
            }
        }
        if (!isEnter) {
    
            return null;
        }

        String name = user.getUsername();
        System.out.println("请输入您的用户选项: 1 -> 管理员  2 -> 普通用户");

        if (role == 1) {
    
            return new Admin(name);
        } else {
    
            return new NormalUser(name);
        }
    }


}