Java入门教程之图书管理系统（由简入繁）(五)
作者：AlexTan
E-mail: [email protected]
我们上一篇博客是用IO来实现图书管理系统的，但在实际情况下，用IO处理来实现是不可能的，为什么呢？ 首先，上一篇的代码我们每运行一次都得读一次和写入一文件，数据量少还行，但如果数据量很多呢？太大呢？ 就比如前天我学习redis的过程中，用redis-dump导出了3.7个G的json数据，结果发现根本无法打开这个json文件，原因是我电脑配置太弱，文件的数据量又太大，所以出现了根本打不开的情况。所以，如果后面数据量过大，还是用IO来实现的话，程序是会崩溃的。因此接下来，我们将把这个程序改成用数据库来实现，数据库我们暂时选用的是mysql。
环境配置：
在编写代码之前，大家需要配置一下环境，我的mysql是用的phpStudy集成的mysql，wamp也可以，或者其他的也可以，反正只需要装上mysql就可以了，怎么装，我这里就不过多阐述了，很简单的。
装好mysql后，我们需要下载java的mysql驱动，下载地址：https://dev.mysql.com/downloads/connector/j/
下载后，配置教程就这个吧，简单一点的：http://jingyan.baidu.com/article/ed15cb1b512a651be36981f4.html
建表：
create database books;
use books;
create table book(id int(6) primary key not null auto_increment,bookname varchar(255),author varchar(255),price float);注意： auto_increment是自增的意思（这个适用于mysql），如果你用的其他数据库，试试 identity(1,1)
配置好，表建立好后，我们就开始编写代码了。
我就直接贴代码了。
代码：
目录结构：
由于我们用的数据库操作，所以前面的book,booklist都去掉了，具体在代码中体现：
Operator.java:
package control;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import jdbc.database;
public class Operator {
public boolean addBook(String bookname,String author,float price)
{
try {
Connection conn = database.getConnection();
Statement stmt = conn.createStatement();
String sql = "insert into book(bookname,author,price) values('"+bookname+"','"+author+"',"+price+")";
//System.out.println(sql);
stmt.execute(sql);
stmt.close();
return true;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
public boolean deleteBook(int id,String bookname)
{
try {
Connection conn = database.getConnection();
Statement stmt = conn.createStatement();
String sql;
if(id != -1)
{
sql = "delete from book where id ="+id;
}
else
{
sql = "delete from book where bookname ='"+bookname+"'";
}
stmt.execute(sql);
stmt.close();
return true;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
public boolean changeBoo(int id,String bookname,String changename)
{
try {
Connection conn = database.getConnection();
Statement stmt = conn.createStatement();
String sql;
if (id != -1)
{
sql = "update book set bookname='"+changename+"'"+" where id="+id;
}
else
{
sql = "update book set bookname='"+changename+"'"+" where bookname='"+bookname+"'";
}
stmt.execute(sql);
stmt.close();
return true;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
public void findBoo(int id,String bookname)
{
try {
Connection conn = database.getConnection();
Statement stmt = conn.createStatement();
String sql;
if (id != -1)
{
sql = "select id,bookname,author,price from book"+" where id="+id;
System.out.println(sql);
}
else
{
sql = "select id,bookname,author,price from book"+" where bookname='"+bookname+"'";
}
ResultSet rs = stmt.executeQuery(sql);
System.out.println("查找成功！您查找的结果为：\n");
while(rs.next()){//如果对象中有数据，就会循环打印出来
System.out.println("编号："+rs.getInt("id")+" 书名："+rs.getString("bookname")+",作者："+rs.getString("author")+",价格："+rs.getFloat("price"));
}
rs.close();
stmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void printAllbook()
{
//3.通过数据库的连接操作数据库，实现增删改查
try {
Connection conn = database.getConnection();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("select id,bookname,author,price from book");//选择import java.sql.ResultSet;
while(rs.next()){//如果对象中有数据，就会循环打印出来
System.out.println("编号："+rs.getInt("id")+" 书名："+rs.getString("bookname")+",作者："+rs.getString("author")+",价格："+rs.getFloat("price"));
}
rs.close();
stmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public boolean clearBook()
{
try {
Connection conn = database.getConnection();
Statement stmt = conn.createStatement();
String sql = "truncate table book";
stmt.execute(sql);
stmt.close();
return true;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
}
database.py:
package jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class database {
private static final String URL="jdbc:mysql://localhost:3306/books";
private static final String NAME="root";
private static final String PASSWORD="root";
private static Connection conn=null;//静态代码块（将加载驱动、连接数据库放入静态块中）
static{
try {
//1.加载驱动程序
Class.forName("com.mysql.jdbc.Driver");
//2.获得数据库的连接
conn = DriverManager.getConnection(URL, NAME, PASSWORD);
System.out.println("数据库连接成功！");
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
//对外提供一个方法来获取数据库连接
public static Connection getConnection(){
return conn;
}
//相当于c++中的析构函数
protected void finalize() throws java.lang.Throwable
{
conn.close();
}
}
MainClass.java:
package ui;
import java.util.Scanner;
import control.Operator;
public class MainClass {
public MainClass()
{
Scanner scan = new Scanner(System.in);
printMenu();
while(true)
{
//读取用户输入
int choice = scan.nextInt();
if(choice == 6)
{
System.out.println("成功退出系统，欢迎再次光临！");
break;
}
switch(choice)
{
case 1: addBook(); break;
case 2: deleteBoo(); break;
case 3: changeBoo(); break;
case 4: findBoo(); break;
case 5: clearBoo(); break;
default: System.out.println("输入非法"); printMenu(); continue;
}
}
/*
while(true)
{
//根据用户输入调用不同方法
if(choice == 1)
{
addBook();
}
else if(choice == 2)
{
deleteBoo();
}
else if(choice == 3)
{
changeBoo();
}
else if(choice == 4)
{
findBoo();
}
else if(choice == 5)
{
System.out.println("成功退出系统，欢迎再次光临！");
break;
}
}
*/
}
void printMenu()
{
//打印菜单
System.out.println("欢迎...");
System.out.println("增加图书...1");
System.out.println("删除图书...2");
System.out.println("修改图书...3");
System.out.println("查询图书...4");
System.out.println("清空图书...5");
System.out.println("退出系统...6");
}
void clearBoo()
{
Operator operator = new Operator();
boolean isSuccess = operator.clearBook();
if(isSuccess)
{
System.out.println("清空成功！");
}
else
{
System.out.println("清空失败！");
}
}
void addBook()
{
Scanner scan = new Scanner(System.in);
System.out.println("请输入图书名：");
String bookname = scan.next();
System.out.println("请输入作者：");
String author = scan.next();
System.out.println("请输入单价：");
float price = scan.nextFloat();
Operator operator = new Operator();
boolean isSuccess = operator.addBook(bookname, author, price);
if(isSuccess)
{
System.out.println("增加成功！");
}
else
{
System.out.println("增加失败！");
}
operator.printAllbook();
}
void deleteBoo()
{
Scanner scan = new Scanner(System.in);
String name = "";
while(true)
{
System.out.println("请输入按哪种方法删除图书：1、编号/2、书名/3、返回主菜单");
int choose = scan.nextInt();
int id = -1;
if(choose == 1)
{
System.out.println("请输入要删除的书的编号：");
id = scan.nextInt();
Operator operator = new Operator();
//System.out.println(id);
if(id > -1)
{
boolean isSuccess = operator.deleteBook(id,name);
if(isSuccess)
System.out.println("删除成功！");
else
System.out.println("删除失败！");
operator.printAllbook();
}
else
{
System.out.println("输入错误！");
}
}
else if(choose == 2)
{
System.out.println("请输入您要删除的书名：");
name = scan.next();
Operator operator = new Operator();
if(name != "")
{
boolean isSuccess = operator.deleteBook(id,name);
if(isSuccess)
System.out.println("删除成功！");
else
System.out.println("删除失败！");
operator.printAllbook();
}
else
{
System.out.println("未查找到您想要的书名");
}
}
else if(choose == 3)
{
printMenu();
break;
}
else
{
System.out.println("输入非法！");
}
}
}
void changeBoo()
{
Scanner scan = new Scanner(System.in);
String name = "";
while(true)
{
System.out.println("请输入按哪种方法修改图书：1、编号/2、书名/3、返回主菜单");
int choose = scan.nextInt();
int id = -1;
if(choose == 1)
{
System.out.println("请输入要修改的书的编号：");
id = scan.nextInt();
Operator operator = new Operator();
if(id > -1)
{
System.out.println("请输入你要修改为什么书名：");
String str = scan.next();
boolean isSuccess = operator.changeBoo(id,str,name);
if(isSuccess)
System.out.println("修改成功！");
else
System.out.println("修改失败！");
operator.printAllbook();
}
else
{
System.out.println("输入错误！");
}
}
else if(choose == 2)
{
System.out.println("请输入您要修改的书名：");
name = scan.next();
Operator operator = new Operator();
if(name != "")
{
System.out.println("请输入你要修改为什么书名：");
String str = scan.next();
boolean isSuccess = operator.changeBoo(id,str,name);
if(isSuccess)
System.out.println("修改成功！");
else
System.out.println("修改失败！");
operator.printAllbook();
}
}
else if(choose == 3)
{
printMenu();
break;
}
else
{
System.out.println("输入非法！");
}
}
}
void findBoo()
{
Scanner scan = new Scanner(System.in);
Operator operator = new Operator();
String name = "";
int id = -1;
while(true)
{
System.out.println("请输入按哪种方法查找图书：1、编号/2、书名/3、返回主菜单");
int choose = scan.nextInt();
if(choose == 1)
{
System.out.println("请输入要查找的书的编号：");
id = scan.nextInt();
if(id > -1)
{
operator.findBoo(id,name);
}
else
{
System.out.println("输入错误！");
}
}
else if(choose == 2)
{
System.out.println("请输入您要查找的书名：");
name = scan.next();
if(name != "")
{
operator.findBoo(id,name);
}
}
else if(choose == 3)
{
printMenu();
break;
}
else
{
System.out.println("输入非法！");
}
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
new MainClass();
}
}
那么，这样我们就用数据库实现了图书管理系统，用数据库实现的一个很大的优点就是极大的简化了“增删改查”的操作（大家从代码量也能看出来），同时几乎也不用担心数据量过大的问题了。
请期待下一篇：Java入门教程之图书管理系统（由简入繁）(六)
转载请注明出处：http://blog.csdn.net/alextan_/article/details/67640511