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：
- 对于普通用户：查看书籍列表，查询指定书籍，借书还书。
- 对于 管理员：查看书籍列表，新增删除书籍。
二、准备数据库
创建用户表和书籍表
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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,'金瓶梅','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
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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
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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
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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
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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
- 1.先把数据库链接的操作封装好
- 2.再把针对书籍表的增删查改操作封装好
- 3.再把针对用户表的操作封装好
数据库链接操作
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//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
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//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
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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）
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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
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public interface ioperation { void work();} |
添加书籍操作
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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
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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
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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
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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
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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
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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
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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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原文链接：https://blog.csdn.net/m0_52276165/article/details/120469926
