Mysql实战练习之简单图书管理系统

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