用資料庫撰寫快遞e站（本文只寫了idea方面的代碼）

##成品如下：

一、IDEA如何連接資料庫

第一種方法：直接在方法體中增加連接資訊
優點：如果僅使用一次資料庫操作可選擇
缺點：多次資料庫操作每次都需要寫，麻煩

public void select() {

        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            //1.注冊驅動
            Class.forName("com.mysql.jdbc.Driver");
            //2.定義sql
            String sql = "select * from kuaidi";
            //3.獲取conn
            conn = DriverManager.getConnection("jdbc:mysql:///kuaidi", "root", "123");
            //4.獲取執行sql物件Statement
            stmt = conn.createStatement();
            //5.執行sql
            rs = stmt.executeQuery(sql);
            //6處理結果
            while (rs.next()) {
                int danhao = rs.getInt(1);
                int qujianma = rs.getInt(2);
                String gongsi = rs.getString("gongsi");
                String guizi = rs.getString(4);
                System.out.println("單號為：" + danhao + "   " + "取件碼為：" + qujianma + "   " + "公司是：" + gongsi + "    " + "柜子在第" + guizi + "個");
            }

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
            if (stmt != null) {
                try {
                    stmt.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }

            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }

            if (rs != null) {
                try {
                    rs.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }


        }
    }

方法二：
建立一個JDBCHelper和一個存盤資料庫賬號密碼的Properties，來幫助快速加載驅動以及釋放記憶體
優點：只需要寫一次，用的時候呼叫即可
缺點：一次要寫很多

釋放記憶體的時候可能傳入兩個或者三個引數需要釋放，所以用多載形式來解決

    private static String url;
    private static String user;
    private static String password;
    private static String driver;

    /**
     * 檔案的讀取，只需要讀取一次即可
     */
    static {
        //讀取資源檔案，并獲取值
        try {
            //1.創建properties集合類
            Properties pro = new Properties();
            //2.加載檔案
            //獲取src路徑下的檔案的方式--->ClassLoader類加載器
            ClassLoader classLoader = JDBCHelper.class.getClassLoader();
            URL res = classLoader.getResource("jdbc.properties");
            String path = res.getPath();
            
            //pro.load(new FileReader("src/jdbc.properties"));
            pro.load(new FileReader(path));

            url = pro.getProperty("url");
            user = pro.getProperty("user");
            password = pro.getProperty("password");
            driver = pro.getProperty("driver");

            Class.forName(driver);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    /**
     * 獲取連接
     *
     * @return連接物件
     */
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url, user, password);
    }
    /**
     * 釋放資源
     *
     * @param stmt
     * @param conn
     */
    public static void close(Statement stmt, Connection conn) {
        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }
//釋放記憶體
    public static void close(ResultSet rs, Statement stmt, Connection conn) {
        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }


    }

二、方法代碼的實作

1.快遞員增加快遞

代碼如下：

public class Add {
    Connection conn = null;
    Statement stmt = null;
    Random r= new Random();
    public void addq(int danhao,String gongsi){
        try {
            conn = JDBCHelper.getConnection();
            int qujianma = r.nextInt((999999)+1);
            String guizi = Integer.toString(r.nextInt(100)+1);
            String sql = "insert into kuaidi values(" + danhao + "," + qujianma+",'"+gongsi+"','"+guizi+"')";
            stmt = conn.createStatement();
            int a = stmt.executeUpdate(sql);
            System.out.println("取件碼為："+qujianma);
            if(a>0){
                System.out.println("添加成功");
            }
            else {
                System.out.println("添加失敗");
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }
    }

2.快遞員洗掉快遞

代碼如下：

public class Delete {

    Connection conn = null;
    Statement stmt = null;

    public void delete(int danhao) {

        try {
            conn = JDBCHelper.getConnection();
            String sql = "delete from kuaidi where danhao = "+danhao;

            stmt = conn.createStatement();
            int a = stmt.executeUpdate(sql);
            if(a>0){
                System.out.println("洗掉成功");
            }
            else {
                System.out.println("洗掉失敗");
            }

        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    finally {
        JDBCHelper.close(stmt,conn);
    }
}

主要內容代碼：

public class Imp {
public static void main(String[] args) {
kuaidi();
}

public static void kuaidi() {
    System.out.println("====歡迎使用新職課快遞柜====");
    Scanner sc = new Scanner(System.in);
    Random r = new Random();
    while (true) {

        System.out.println("請輸入你的身份：1-快遞員，2-用戶");
        try {
            int a = sc.nextInt();

            if (a < 1 || a > 2) {
                System.out.println("輸入有誤，請重新輸入");
            } else if (a == 1) {
                System.out.println("====歡迎使用新職課快遞柜====");
                System.out.println("請選擇操作：1-存快遞 2-洗掉快遞 3-修改快遞資訊 4-查看所有快遞");
                int b = sc.nextInt();
                switch (b) {
                    case 1: {
                        System.out.println("====歡迎使用新職課快遞柜====");
                        System.out.println("請輸入快遞單號：");
                        int danhao = sc.nextInt();
                        System.out.println("請輸入公司名稱：");
                        String gongsi = sc.next();
                        Add add = new Add();
                        add.addq(danhao, gongsi);

                        break;
                    }
                    case 2: {
                        System.out.println("====歡迎使用新職課快遞柜====");
                        System.out.print("請輸入要洗掉的訂單號：");
                        int dingdan = sc.nextInt();
                        Delete delete = new Delete();
                        delete.delete(dingdan);
                        break;
                    }
                    case 3: {
                        System.out.println("====歡迎使用新職課快遞柜====");
                        System.out.print("請輸入要修改的訂單號：");
                        int danhao = sc.nextInt();
                        Alter al = new Alter();
                        boolean q = al.select(danhao);
                        if (q = true) {
                            System.out.println("請輸入更改后的單號");
                            int afdanhao = sc.nextInt();
                            al.alter(afdanhao, danhao);
                        } else {
                            System.out.println("請核實訂單號");
                        }

                        break;
                    }
                    case 4: {
                        System.out.println("====歡迎使用新職課快遞柜====");
                        SelectAll s = new SelectAll();
                        s.select();
                    }
                }

            } else if (a == 2) {
                System.out.println("====歡迎使用新職課快遞柜====");
                System.out.println("請輸入取件碼");
                int qujianma = sc.nextInt();
                Take t = new Take();
                t.take(qujianma);

            }


        } catch (InputMismatchException e) {
            System.out.println();
            System.out.println("請輸入數字序號!!!!!!!!");
            System.out.println();
            kuaidi();
        }
    }

}

}

別的幾個代碼塊都大同小異，只需要修改sql陳述句即可

如有需要全部代碼，或者有疑問的同學私信我就可以了