Java入門教程之圖書管理系統(由簡入繁)(五)

AlexTan_發表於2017-03-28

作者:AlexTan

E-mail: alextanbz@gmail.com


我們上一篇部落格是用IO來實現圖書管理系統的,但在實際情況下,用IO處理來實現是不可能的,為什麼呢? 首先,上一篇的程式碼我們每執行一次都得讀一次和寫入一檔案,資料量少還行,但如果資料量很多呢?太大呢?  就比如前天我學習redis的過程中,用redis-dump匯出了3.7個G的json資料,結果發現根本無法開啟這個json檔案,原因是我電腦配置太弱,檔案的資料量又太大,所以出現了根本打不開的情況。所以,如果後面資料量過大,還是用IO來實現的話,程式是會崩潰的。因此接下來,我們將把這個程式改成用資料庫來實現,資料庫我們暫時選用的是mysql。


環境配置:

在編寫程式碼之前,大家需要配置一下環境,我的mysql是用的phpStudy整合的mysql,wamp也可以,或者其他的也可以,反正只需要裝上mysql就可以了,怎麼裝,我這裡就不過多闡述了,很簡單的。

裝好mysql後,我們需要下載java的mysql驅動,下載地址:https://dev.mysql.com/downloads/connector/j/

下載後,配置教程就這個吧,簡單一點的: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(這個適用於mysql),如果你用的其他資料庫,試試 identity(1,1)


配置好,表建立好後,我們就開始編寫程式碼了。

我就直接貼程式碼了。

程式碼:


目錄結構:

由於我們用的資料庫操作,所以前面的book,booklist都去掉了,具體在程式碼中體現:

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("查詢成功!您查詢的結果為:\n");
			while(rs.next()){//如果物件中有資料,就會迴圈列印出來
				System.out.println("編號:"+rs.getInt("id")+" 書名:"+rs.getString("bookname")+",作者:"+rs.getString("author")+",價格:"+rs.getFloat("price"));
			}
			rs.close();
			stmt.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	
	public void printAllbook()
	{
		//3.通過資料庫的連線運算元據庫,實現增刪改查
		try {
			Connection conn = database.getConnection();
			Statement stmt = conn.createStatement();
			ResultSet rs = stmt.executeQuery("select id,bookname,author,price from book");//選擇import java.sql.ResultSet;
			while(rs.next()){//如果物件中有資料,就會迴圈列印出來
				System.out.println("編號:"+rs.getInt("id")+" 書名:"+rs.getString("bookname")+",作者:"+rs.getString("author")+",價格:"+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;//靜態程式碼塊(將載入驅動、連線資料庫放入靜態塊中)
	static{
		try {
				//1.載入驅動程式
				Class.forName("com.mysql.jdbc.Driver");
				//2.獲得資料庫的連線
				conn = DriverManager.getConnection(URL, NAME, PASSWORD);
				System.out.println("資料庫連線成功!");
				} catch (ClassNotFoundException e) {
					e.printStackTrace();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
	
	//對外提供一個方法來獲取資料庫連線
	public static Connection getConnection(){
		return conn;
	}
	
	//相當於c++中的解構函式
	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)
		{
			//讀取使用者輸入
			int choice = scan.nextInt();
			
			if(choice == 6)
			{
				System.out.println("成功退出系統,歡迎再次光臨!");
				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("輸入非法"); printMenu(); continue;
			}
		}
		
		
		/*
		while(true)
		{	
			//根據使用者輸入呼叫不同方法
			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("成功退出系統,歡迎再次光臨!");
				break;
			}
		}
		*/
	}
	void printMenu()
	{
		//列印選單
		System.out.println("歡迎...");
		System.out.println("增加圖書...1");
		System.out.println("刪除圖書...2");
		System.out.println("修改圖書...3");
		System.out.println("查詢圖書...4");
		System.out.println("清空圖書...5");
		System.out.println("退出系統...6");	
	}
	
	void clearBoo()
	{
		Operator operator = new Operator();
		boolean isSuccess = operator.clearBook();
		if(isSuccess)
		{
			System.out.println("清空成功!");
		}
		else
		{
			System.out.println("清空失敗!");
		}
	}
	
	void addBook()
	{
		Scanner scan = new Scanner(System.in);
		System.out.println("請輸入圖書名:");
		String bookname = scan.next();
		System.out.println("請輸入作者:");
		String author = scan.next();
		System.out.println("請輸入單價:");
		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("增加失敗!");
		}
		operator.printAllbook();
	}
	
	void deleteBoo()
	{
		Scanner scan = new Scanner(System.in);
		String name = "";
		while(true)
		{
			System.out.println("請輸入按哪種方法刪除圖書:1、編號/2、書名/3、返回主選單");
			int choose = scan.nextInt();
			int id = -1;
			if(choose == 1)
			{
				System.out.println("請輸入要刪除的書的編號:");
				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("刪除成功!");
					else
						System.out.println("刪除失敗!");
					operator.printAllbook();
				}
				else
				{
					System.out.println("輸入錯誤!");
				}
			}
			else if(choose == 2)
			{
				System.out.println("請輸入您要刪除的書名:");
				name = scan.next();
				Operator operator = new Operator();
				if(name != "")
				{
					boolean isSuccess = operator.deleteBook(id,name);
					if(isSuccess)
						System.out.println("刪除成功!");
					else
						System.out.println("刪除失敗!");
					operator.printAllbook();
				}
				else
				{
						System.out.println("未查詢到您想要的書名");
				}	
			}
			else if(choose == 3)
			{
				printMenu();
				break;
			}
			else
			{
				System.out.println("輸入非法!");
			}
		}
	}
	
	void changeBoo()
	{
		Scanner scan = new Scanner(System.in);
		String name = "";
		while(true)
		{
			System.out.println("請輸入按哪種方法修改圖書:1、編號/2、書名/3、返回主選單");
			int choose = scan.nextInt();
			int id = -1;
			if(choose == 1)
			{
				System.out.println("請輸入要修改的書的編號:");
				id = scan.nextInt();
				Operator operator = new Operator();
				if(id > -1)
				{
					System.out.println("請輸入你要修改為什麼書名:");
					String str = scan.next();
					boolean isSuccess = operator.changeBoo(id,str,name);
					if(isSuccess)
						System.out.println("修改成功!");
					else
						System.out.println("修改失敗!");
					
					operator.printAllbook();
				}
				else
				{
					System.out.println("輸入錯誤!");
				}
			}
			else if(choose == 2)
			{
				System.out.println("請輸入您要修改的書名:");
				name = scan.next();
				Operator operator = new Operator();
				if(name != "")
				{	
					System.out.println("請輸入你要修改為什麼書名:");
					String str = scan.next();
					boolean isSuccess = operator.changeBoo(id,str,name);
					if(isSuccess)
						System.out.println("修改成功!");
					else
						System.out.println("修改失敗!");
					operator.printAllbook();
				}
			}
			else if(choose == 3)
			{
				printMenu();
				break;
			}
			else
			{
				System.out.println("輸入非法!");
			}
		}
	}
	
	void findBoo()
	{
		Scanner scan = new Scanner(System.in);
		Operator operator = new Operator();
		String name = "";
		int id = -1;
		while(true)
		{
			System.out.println("請輸入按哪種方法查詢圖書:1、編號/2、書名/3、返回主選單");
			int choose = scan.nextInt();
			if(choose == 1)
			{
				System.out.println("請輸入要查詢的書的編號:");
				id = scan.nextInt();
				if(id > -1)
				{
					operator.findBoo(id,name);
				}
				else
				{
					System.out.println("輸入錯誤!");
				}
			}
			else if(choose == 2)
			{
				System.out.println("請輸入您要查詢的書名:");
				name = scan.next();
				if(name != "")
				{
					operator.findBoo(id,name);
				}
			}
			else if(choose == 3)
			{
				printMenu();
				break;
			}
			else
			{
				System.out.println("輸入非法!");
			}
		}
	}
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		new MainClass();
	}

}

那麼,這樣我們就用資料庫實現了圖書管理系統,用資料庫實現的一個很大的優點就是極大的簡化了“增刪改查”的操作(大家從程式碼量也能看出來),同時幾乎也不用擔心資料量過大的問題了。


請期待下一篇:Java入門教程之圖書管理系統(由簡入繁)(六)

轉載請註明出處:http://blog.csdn.net/alextan_/article/details/67640511


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