Mysql实战练习之简单图书管理系统- Starterknow

四、封装数据库相关操作

一、梳理功能

1.能够表示书籍信息，针对每本书来说，序号，书名，作者，价格，类型。

2.能够表示用户信息，普通用户，管理员。

3.支持的操作：

二、准备数据库

创建用户表和书籍表

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);

drop table if exists user;

//同样设置 userid为自增主键并且用户名字不重复

create table user(

userId int primary key auto_increment,

username varchar(20) unique,

password varchar(20),

isAdmin int

);

— 插入一些书籍

insert into book values(null,’西游记’,’吴承恩’,10000,’古典小说’,0);

insert into book values(null,’三国演义’,’罗贯中’,10000,’古典小说’,0);

insert into book values(null,’水浒传’,’施耐庵’,10000,’古典小说’,0);

insert into book values(null,’X’,’兰陵笑笑生’,10000,’古典小说’,0);

–插入一些用户

insert into user values(null,’admin’,’123′,1);

insert into user values(null,’zhangsan’,’123′,0);

三、构造和数据库相关的实体类

书籍

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 +

            ‘}’;

}

用户

有两种用户，一种为普通用户，另一种为管理员，管理员和普通用户看到的menu不同，管理员和普通用户的类方法也不同

先定义一个抽象类User 让普通用户NoramlUser和管理员类Admin来继承User类

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 + ‘\” +

            ‘}’;

}

}

NormalUser类

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

      };

}

@Override

public 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;

}

}

Admin类

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

      };

}

@Override

public 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;

}

}

四、封装数据库相关操作

数据库链接操作

//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();

      }

}

}

针对书籍表操作

//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;

      }

}

针对用户表的操作

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;

}

}

编写主逻辑（main方法和login方法）

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;

}

}

编写operation各种细节

将所有operations操作放在一个包中，定义一个接口operations，所有操作实现这个接口并重写方法

IOperation接口

public interface IOperation {

void work();

}

添加书籍操作

public class AddOperation implements IOperation{

@Override

public 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”);

}

}

借书操作

public class BorrowOperation implements IOperation {

@Override

public 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);

}

}

删除书籍操作

public class DelOperation implements IOperation{

@Override

public 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”);

}

}

查看书籍列表操作

public class DisplayOperation implements IOperation {

@Override

public 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”);

}

}

退出系统操作

public class ExitOperation implements IOperation{

@Override

public void work() {

System.out.println(“退出程序”);

System.exit(0);

}

}

查找书籍操作

public class FindOperation implements IOperation{

@Override

public 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”);

}

}

还书操作

public class ReturnOperation implements IOperation{

@Override

public 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”);

      }

}

}

总结：简单的图书管理系统，通过练习掌握简单JDBC语法和API，同时可以帮助理解java中多态继承等概念。

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原创文章，作者：starterknow，如若转载，请注明出处：https://www.starterknow.com/117683.html

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