目录

• 一、梳理功能
• 二、准备数据库
• 三、构造和数据库相关的实体类
• • 书籍
  • 用户
  • NormalUser类
• 四、封装数据库相关操作
• • 数据库链接操作
  • 针对书籍表操作
  • 针对用户表的操作
  • 编写主逻辑（main方法和login方法）
  • 编写operation各种细节
  • • 添加书籍操作
    • 借书操作
    • 删除书籍操作
    • 查看书籍列表操作
    • 退出系统操作
    • 查找书籍操作
    • 还书操作

create database if not exists java100_bookmanager;
use java100_bookmanager;
drop table if exists book;
//设置id为自增主键
create table book(id int primary  key auto_increment,name varchar(20),author varchar(20),price int,type varchar(20),isBorrowed int);

public class Books {private int bookId;//书籍编号private String name;//书名private String author;//作者private int price;//价格private String type;//类型private boolean isBorrowed;//是否被借阅//set get方法

public int getBookId() {return bookId;
}public void setBookId(int bookId) {this.bookId = bookId;
}public String getName() {return name;
}public void setName(String name) {this.name = name;
}public String getAuthor() {return author;
}public void setAuthor(String author) {this.author = author;
}public int getPrice() {return price;
}public void setPrice(int price) {this.price = price;
}public String getType() {return type;
}public void setType(String type) {this.type = type;
}public boolean isBorrowed() {return isBorrowed;
}public void setBorrowed(boolean borrowed) {isBorrowed = borrowed;
}@Override
public String toString() {return "Book{" +"bookId=" + bookId +", name='" + name + '\'' +", author='" + author + '\'' +", price=" + price +", type='" + type + '\'' +", isBorrowed=" + isBorrowed +'}';
}

abstract public class user {private int userId;private String userName;private String passWord;

IOperation[] operations;//方法数组，表示user类所包含的方法
abstract int menu();//子类要重写menu方法，因为两个子类看到的menu不同
public void doOperation(int choice){//此方法来执行一些操作，如借书还书等operations[choice].work();
}public int getUserId() {return userId;
}public void setUserId(int userId) {this.userId = userId;
}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;
}@Override
public String toString() {return "user{" +"userId=" + userId +", userName='" + userName + '\'' +", passWord='" + passWord + '\'' +'}';
}

public class NormalUser extends user{public NormalUser(){this.operations=new IOperation[]{//之后单独开辟一个包，包里存储和实现这些方法new ExitOperation(),//退出系统new DisplayOperation(),//查看书籍列表new FindOperation(),//查找书籍new BorrowOperation(),//借阅书籍new ReturnOperation(),//还书};}@Overridepublic int menu() {//重写父类menu方法System.out.println("========================");System.out.println("欢迎您，"+this.getUserName()+"!");System.out.println("1.查看书籍列表");System.out.println("2.查找指定书籍");System.out.println("3.借阅书籍");System.out.println("4.归还书籍");System.out.println("0.退出系统");System.out.println("========================");System.out.println("请输入选项");Scanner sc=new Scanner(System.in);int choice=sc.nextInt();return choice;}
}

public class Admin extends user {public Admin(){this.operations=new IOperation[]{new ExitOperation(),//退出系统new DisplayOperation(),//查看书籍列表new FindOperation(),//查找书籍new AddOperation(),//添加书籍new DelOperation(),//删除书籍};}@Overridepublic int menu() {System.out.println("========================");System.out.println("欢迎您，"+this.getUserName()+"您是管理员!");System.out.println("1.查看书籍列表");System.out.println("2.查找指定书籍");System.out.println("3.新增书籍");System.out.println("4.删除书籍");System.out.println("0.退出系统");System.out.println("========================");System.out.println("请输入选项");Scanner sc=new Scanner(System.in);int choice=sc.nextInt();return choice;}
}

//在这里封装数据库的连接操作
public class DBUtil {
//设置url 账号密码 根据个人设置private static final String URL="jdbc:mysql://127.0.0.1:3306/java100_bookmanager?characterEncoding=utf8&&useSSL=false";private static final String USERNAME="root";private static final String PASSWORD="q986681563";//饿汉模式//类加载阶段就会调用静态代码块进行实例化/*private static DataSource dataSource=new MysqlDataSource();

static{((MysqlDataSource)dataSource).setUrl(URL);((MysqlDataSource)dataSource).setUser(USERNAME);((MysqlDataSource)dataSource).setPassword(PASSWORD);
}*/
//懒汉模式
//只有首次调用getDataSource方法 才会实例化
private static DataSource dataSource=null;
public static DataSource getDataSource(){if(dataSource==null){dataSource=new MysqlDataSource();((MysqlDataSource)dataSource).setUrl(URL);((MysqlDataSource)dataSource).setUser(USERNAME);((MysqlDataSource)dataSource).setPassword(PASSWORD);}return dataSource;
}
public static Connection getConnection() throws SQLException {return getDataSource().getConnection();
}
public static void close(ResultSet resultSet, PreparedStatement statement,Connection connection){//释放资源
//注释掉的方式更安全/*if(resultSet!=null){try {resultSet.close();} catch (SQLException e) {e.printStackTrace();}}if(statement!=null){try {statement.close();} catch (SQLException e) {e.printStackTrace();}}if(connection!=null){try {connection.close();} catch (SQLException e) {e.printStackTrace();}}*/try {if(resultSet!=null) resultSet.close();if(statement!=null) statement.close();if(connection!=null) connection.close();} catch (SQLException e) {e.printStackTrace();}
}

//DAO Data Access Object 数据访问对象
public class BookDAO {//1.新增书籍public boolean add(Books book){Connection connection=null;PreparedStatement statement=null;try {connection= DBUtil.getConnection();String sql="insert into book values(null,?,?,?,?,?)";statement=connection.prepareStatement(sql);statement.setString(1,book.getName());statement.setString(2,book.getAuthor());statement.setInt(3,book.getPrice());statement.setString(4,book.getType());statement.setInt(5,book.isBorrowed()?1:0);int ret=statement.executeUpdate();if(ret!=1) return false;return true;} catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(null,statement,connection);}return false;}//2.查看所有书籍public List<Books> selectAll(){List<Books> list=new ArrayList<>();Connection connection=null;PreparedStatement statement=null;ResultSet resultSet=null;try {connection=DBUtil.getConnection();String sql="select*from book";statement=connection.prepareStatement(sql);resultSet=statement.executeQuery();while(resultSet.next()){Books book=new Books();book.setBookId(resultSet.getInt("id"));book.setName(resultSet.getString("name"));book.setAuthor(resultSet.getString("author"));book.setPrice(resultSet.getInt("price"));book.setType(resultSet.getString("type"));book.setBorrowed(resultSet.getInt("isBorrowed")==1);list.add(book);}} catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(resultSet,statement,connection);}return list;}//3.根据名字找书籍public List<Books> selectByName(String name) {List<Books> list=new ArrayList<>();Connection connection=null;PreparedStatement statement=null;ResultSet resultSet=null;try {connection=DBUtil.getConnection();String sql="select* from book where name=?";statement=connection.prepareStatement(sql);statement.setString(1,name);resultSet=statement.executeQuery();while(resultSet.next()){Books book=new Books();book.setBookId(resultSet.getInt("Id"));book.setName(resultSet.getString("name"));book.setAuthor(resultSet.getString("author"));book.setType(resultSet.getString("type"));book.setPrice(resultSet.getInt("price"));book.setBorrowed(resultSet.getInt("isBorrowed")==1);list.add(book);}} catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(resultSet,statement,connection);}return list;}//4.删除书籍public boolean delete(int bookId){Connection connection=null;PreparedStatement statement=null;try {connection=DBUtil.getConnection();String sql="delete from book where id=?";statement=connection.prepareStatement(sql);statement.setInt(1,bookId);int ret=statement.executeUpdate();if(ret!=1) return false;return true;} catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(null,statement,connection);}return false;}//5.借书public boolean borrowBook(int bookId){Connection connection=null;PreparedStatement statement=null;PreparedStatement statement2=null;ResultSet resultSet=null;try {connection=DBUtil.getConnection();String sql="select * from book where id=?";statement=connection.prepareStatement(sql);statement.setInt(1,bookId);resultSet=statement.executeQuery();if(resultSet.next()){boolean isBorrowed=(resultSet.getInt("isBorrowed")==1);if(isBorrowed){System.out.println("书已借出，无法再次借出！ bookId="+bookId);return false;}}else{System.out.println("书不存在 bookId="+bookId);return false;}sql="update book set isBorrowed=1 where id=?";statement2=connection.prepareStatement(sql);statement2.setInt(1,bookId);int ret = statement2.executeUpdate();if(ret!=1) {System.out.println("借阅失败");return false;}System.out.println("借阅成功");return true;} catch (SQLException e) {e.printStackTrace();}finally {if(resultSet!=null) {try {connection.close();} catch (SQLException throwables) {throwables.printStackTrace();}}if(statement!=null) {try {statement.close();} catch (SQLException throwables) {throwables.printStackTrace();}}if(statement2!=null) {try {statement2.close();} catch (SQLException throwables) {throwables.printStackTrace();}}if(connection!=null){try {connection.close();} catch (SQLException throwables) {throwables.printStackTrace();}}}return false;}//6.归还public boolean returnBook(int bookId){Connection connection=null;PreparedStatement statement=null;PreparedStatement statement2=null;ResultSet resultSet=null;try {connection=DBUtil.getConnection();String sql="select* from book where id=?";statement=connection.prepareStatement(sql);statement.setInt(1,bookId);resultSet= statement.executeQuery();if(resultSet.next()){boolean isBorrowed=(resultSet.getInt("isBorrowed")==1);if(!isBorrowed){System.out.println("书没有被借出，不需要归还 bookId="+bookId);return false;}}else{System.out.println("没有该书！ bookId="+bookId);return false;}sql="update book set isBorrowed=0 where id=?";statement2=connection.prepareStatement(sql);statement2.setInt(1,bookId);int ret = statement2.executeUpdate();if(ret!=1) return false;return true;} catch (SQLException e) {e.printStackTrace();}finally {if(resultSet!=null) {try {connection.close();} catch (SQLException throwables) {throwables.printStackTrace();}}if(statement!=null) {try {statement.close();} catch (SQLException throwables) {throwables.printStackTrace();}}if(statement2!=null) {try {statement2.close();} catch (SQLException throwables) {throwables.printStackTrace();}}if(connection!=null){try {connection.close();} catch (SQLException throwables) {throwables.printStackTrace();}}}return false;}}

public class UserDao {//根据用户名找密码的逻辑//username是unique约束的public user selectByName(String name){Connection connection=null;PreparedStatement statement=null;ResultSet resultSet=null;try {connection=DBUtil.getConnection();String sql="select* from user where username=?";statement=connection.prepareStatement(sql);statement.setString(1,name);resultSet = statement.executeQuery();if(resultSet.next()){boolean isAdmin=(resultSet.getInt("isAdmin")==1);user users=null;if(isAdmin){users=new Admin();}else users=new NormalUser();users.setPassWord(resultSet.getString("password"));users.setUserId(resultSet.getInt("userId"));users.setUserName(resultSet.getString("username"));return users;}

    } catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(resultSet,statement,connection);}return null;
}

public class Main {public static void main(String[] args) {user users=login();while(true){int choice=users.menu();users.doOperation(choice);}}private static user login(){Scanner sc=new Scanner(System.in);System.out.println("请输入用户名");String name=sc.next();System.out.println("请输入密码");String password=sc.next();UserDao userDao=new UserDao();user users=userDao.selectByName(name);if(users==null){System.out.println("登陆失败！");System.exit(0);}if(!users.getPassWord().equals(password)){System.out.println("密码错误");System.exit(0);}return users;}
}

public interface IOperation {void work();
}

public class AddOperation implements IOperation{@Overridepublic void work() {System.out.println("新增书籍！");Scanner sc=new Scanner(System.in);System.out.println("请输入书名");String name=sc.next();System.out.println("请输入作者");String author=sc.next();System.out.println("请输入价格");int price=sc.nextInt();System.out.println("请输入类别");String type=sc.next();Books book=new Books();book.setName(name);book.setPrice(price);book.setType(type);book.setAuthor(author);BookDAO bookDAO=new BookDAO();boolean ret=bookDAO.add(book);if(ret) System.out.println("新增成功");else System.out.println("新增失败");}
}

public class BorrowOperation implements IOperation {@Overridepublic void work() {System.out.println("借阅书籍");System.out.println("请输入要借阅的书籍id");Scanner sc=new Scanner(System.in);int id=sc.nextInt();BookDAO bookDAO=new BookDAO();boolean ret = bookDAO.borrowBook(id);}
}

public class DelOperation implements IOperation{@Overridepublic void work() {System.out.println("删除书籍！");Scanner sc=new Scanner(System.in);System.out.println("请输入删除书籍的id");int id=sc.nextInt();BookDAO bookDAO=new BookDAO();boolean ret = bookDAO.delete(id);if(ret) System.out.println("删除成功");else System.out.println("删除失败");}
}

public class DisplayOperation implements IOperation {@Overridepublic void work() {System.out.println("展示所有书籍");BookDAO bookdao=new BookDAO();List<Books> list=bookdao.selectAll();for(Books book:list){System.out.println(book);}System.out.println("展示书籍完毕");}
}

public class ExitOperation implements IOperation{@Overridepublic void work() {System.out.println("退出程序");System.exit(0);}
}

public class FindOperation implements IOperation{@Overridepublic void work() {System.out.println("根据名字查找书籍");System.out.println("请输入书名");Scanner sc=new Scanner(System.in);String name=sc.next();BookDAO bookDAO=new BookDAO();List<Books> books = bookDAO.selectByName(name);for(Books book:books){System.out.println(book);}System.out.println("根据名字查找书籍完毕");}
}

public class ReturnOperation implements IOperation{@Overridepublic void work() {System.out.println("归还书籍！");System.out.println("请输入要归还的书籍的id");Scanner sc=new Scanner(System.in);int id=sc.nextInt();BookDAO bookDAO=new BookDAO();boolean ret = bookDAO.returnBook(id);if(ret){System.out.println("归还成功");}else{System.out.println("归还失败");}}
}