目錄

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擴充套件閱讀

前言

大多數的應用程式在開發之前都需要先進行資料庫設計這一環節，所以本篇就先來記錄在 Flask 中如何使用 Models，也就是 MVC 模式中的 M 。

Models 模型

模型 就是對 資料抽象 並且提供一種 統一的通用訪問介面 方式。
在大多數的 Web 應用中，都會將資料儲存在 關係型資料庫 中，EG. Mysql/Oracle/Postgres 。(當然現在也越來越多的在使用 非關係型資料庫，但本篇只對前者做記錄。) 這就會出現一個問題，怎樣才能讓關係型資料在面向物件程式設計結構的應用程式中得到更好的契合? 問了解決這個問題，在 Web 應用程式開發中引入了 Models 的概念 —— 將關係型資料轉化為一個物件型別

SQLAlchemy

SQLAlchemy 是一個 Python 包，其最底層包裝了對資料庫進入操作的統一介面，然後在最上層提供了物件關係對映(ORM)的實現。

ORM 是在基於不同的資料結構和不同的系統型別之間進行傳遞和轉換資料的計數。簡而言之，SQLAlchemy-ORM 可以把大量的不同型別的資料庫中的資料，轉換成 Python 物件的集合。也就是說，SQLAlchemy-ORM 可以將對這些資料物件的操作轉化為對資料庫的操作。

Flask 為我們提供了 Flask SQLAlchemy，其實就是在 SQLAlchemy 上提供了一層包裝，讓 SQLAlchemy 可以結合 Flask 的一些特性來使用。

安裝 SQLAlchemy

(env) [[email protected]-dev JmilkFan-s-Blog]# pip install flask-sqlalchemy
(env) [[email protected]-dev JmilkFan-s-Blog]# pip freeze > requirements.txt

flask-sqlalchemy 預設支援 SQLite，但是這裡我們會使用 Mysql，所以還需要安裝 SQLAlchemy 和 Mysql 之間的聯結器。

(env) [[email protected]-dev
 
 JmilkFan-s-Blog]# pip install PyMySQL
(env) [[email protected]-dev JmilkFan-s-Blog]# pip freeze > requirements.txt 

安裝 Mysql

wget http://dev.mysql.com/get/mysql-community-release-el7-5.noarch.rpm
rpm -ivh mysql-community-release-el7-5.noarch.rpm
yum install mysql-community-server
service mysqld restart

初始化 MySQL 並設定登陸密碼:

[[email protected] JmilkFan-s-Blog]# mysql_secure_installation

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MySQL
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MySQL to secure it, we'll need the current
password for the root user.  If you've just installed MySQL, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none): 
OK, successfully used password, moving on...

Setting the root password ensures that nobody can log into the MySQL
root user without the proper authorisation.

Set root password? [Y/n] y
New password: 
Re-enter new password: 
Password updated successfully!
Reloading privilege tables..
 ... Success!


By default, a MySQL installation has an anonymous user, allowing anyone
to log into MySQL without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] 
 ... Success!

Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] 
 ... Success!

By default, MySQL comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] 
 - Dropping test database...
ERROR 1008 (HY000) at line 1: Can't drop database 'test'; database doesn't exist
 ... Failed!  Not critical, keep moving...
 - Removing privileges on test database...
 ... Success!

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] 
 ... Success!

All done!  If you've completed all of the above steps, your MySQL
installation should now be secure.

Thanks for using MySQL!

Cleaning up...

建立 SQLAlchemy 和 Mysql 的連線

SQLAlchemy 通過一個特殊的 URI 字串來建立與資料庫的連線，一般的格式如下：

database_type+driver://user:[email protected]_server_ip:port/database_name

我們需要在 config.py 檔案中定義這一 URI：

class Config(object):
    """Base config class."""
    pass

class ProdConfig(Config):
    """Production config class."""
    pass

class DevConfig(Config):
    """Development config class."""
    DEBUG = True
    # MySQL connection
    SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:[email protected]:3306/jmilkfansblog'