#!/usr/bin/env python3
# -*- coding: utf-8 -*-#
#                        Python3 ORM hacking
# 说明：
#     之前分析了一个Python2 ORM的源代码，这次分析一个Python3的源代码，在写法上
# 还是又挺大的区别的。#                                        2016-10-22 深圳 南山平山村 曾剑锋
#
# 源码：
#     https://github.com/michaelliao/awesome-python3-webapp/tree/day-03
#
# 参考文章：
#     1. python logging模块使用教程
#         http://www.jianshu.com/p/feb86c06c4f4
#     2. Python async/await入门
#         https://ipfans.github.io/2015/08/introduction-to-async-and-await/
#     3. 浅析python的metaclass
#         http://jianpx.iteye.com/blog/908121
#     4. Why I got ignored exception when I use aiomysql in python 3.5 #59
#         https://github.com/aio-libs/aiomysql/issues/59
# __author__ = 'Michael Liao'import asyncio, loggingimport aiomysql# SQL日志打印输出模板
def log(sql, args=()):logging.info('SQL: %s' % sql)# 创建数据库连接池
async def create_pool(loop, **kw):logging.info('create database connection pool...')# 标记__pool为文件内全局变量，在其他函数内可以直接访问global __pool__pool = await aiomysql.create_pool(host=kw.get('host', 'localhost'),port=kw.get('port', 3306),user=kw['user'],password=kw['password'],db=kw['db'],charset=kw.get('charset', 'utf8'),autocommit=kw.get('autocommit', True),maxsize=kw.get('maxsize', 10),minsize=kw.get('minsize', 1),loop=loop)# 数据库查询
async def select(sql, args, size=None):# 输出SQL日志信息log(sql, args)global __pool# 从连接池中获取连接,aysnc是异步获取连接async with __pool.get() as conn:async with conn.cursor(aiomysql.DictCursor) as cur:# 合成实际的SQLawait cur.execute(sql.replace('?', '%s'), args or ())# 根据size来获取数据多少行记录if size:rs = await cur.fetchmany(size)else:rs = await cur.fetchall()# 给出获取到的信息条数logging.info('rows returned: %s' % len(rs))return rs# 数据库直接执行SQL
async def execute(sql, args, autocommit=True):log(sql)async with __pool.get() as conn:# 如果不是自动提交if not autocommit:await conn.begin()try:async with conn.cursor(aiomysql.DictCursor) as cur:await cur.execute(sql.replace('?', '%s'), args)# 返回的执行SQL后有效行数,从代码上可以看出，这部分主要是执行更新、插入、删除等SQL语句affected = cur.rowcount# 完成提交工作if not autocommit:await conn.commit()except BaseException as e:# 出现问题，回滚if not autocommit:await conn.rollback()raise       # 直接再次抛出异常return affected # 返回有效行数# 合成可替代参数字符串，先使用'?'代替'%s'
def create_args_string(num):L = []for n in range(num):L.append('?')return ', '.join(L)# 对应数据库中每一个字段的一个域的基类
class Field(object):# 域名、域类型、是否是主键、默认值def __init__(self, name, column_type, primary_key, default):self.name = nameself.column_type = column_typeself.primary_key = primary_keyself.default = default# 重写默认输出的str函数def __str__(self):return '<%s, %s:%s>' % (self.__class__.__name__, self.column_type, self.name)# 字符串类型的域
class StringField(Field):def __init__(self, name=None, primary_key=False, default=None, ddl='varchar(100)'):super().__init__(name, ddl, primary_key, default)# Boolean类型的域
class BooleanField(Field):def __init__(self, name=None, default=False):super().__init__(name, 'boolean', False, default)# 整形类型的域
class IntegerField(Field):def __init__(self, name=None, primary_key=False, default=0):super().__init__(name, 'bigint', primary_key, default)# 浮点类型的域
class FloatField(Field):def __init__(self, name=None, primary_key=False, default=0.0):super().__init__(name, 'real', primary_key, default)# 文本类型的域
class TextField(Field):def __init__(self, name=None, default=None):super().__init__(name, 'text', False, default)# MVC中的Model的元类，主要用于自动生成映射(map)类
class ModelMetaclass(type):# name: 类的名字# bases: 基类，通常是tuple类型# attrs: dict类型，就是类的属性或者函数def __new__(cls, name, bases, attrs):# 过滤掉Model类直接生成的实例类if name=='Model':return type.__new__(cls, name, bases, attrs)# 从类的属性中获取__table__，其实也就是于数据库对应的表名，如果不存在那么就是等于类名tableName = attrs.get('__table__', None) or namelogging.info('found model: %s (table: %s)' % (name, tableName))# 创建映射字典mappings = dict()# 域listfields = []# 主键标记primaryKey = None# 获取类中的所有的键值对for k, v in attrs.items():# 选择Field类型实例的属性作为映射键值if isinstance(v, Field):logging.info('  found mapping: %s ==> %s' % (k, v))# 将当前的键值对放入mapping中mappings[k] = vif v.primary_key:# 防止出现两个、两个以上的主键if primaryKey:raise StandardError('Duplicate primary key for field: %s' % k)primaryKey = kelse:# 将key添加进入fields中，也就是映射类中的属性和数据库中的表的域, 这里面不包含主键fields.append(k)# 前面可能没有找到主键，提示一下if not primaryKey:raise StandardError('Primary key not found.')# 删除这些类属性 防止访问实例属性的时候发生错误，因为实例属性优先级大于类属性for k in mappings.keys():attrs.pop(k)escaped_fields = list(map(lambda f: '`%s`' % f, fields))attrs['__mappings__'] = mappings        # 保存属性和列的映射关系attrs['__table__'] = tableName          # 表名attrs['__primary_key__'] = primaryKey   # 主键属性名attrs['__fields__'] = fields            # 除主键外的属性名# 生成查询SQLattrs['__select__'] = 'select `%s`, %s from `%s`' % (primaryKey, ', '.join(escaped_fields), tableName)# 生成插入SQLattrs['__insert__'] = 'insert into `%s` (%s, `%s`) values (%s)' % (tableName, ', '.join(escaped_fields), primaryKey, create_args_string(len(escaped_fields) + 1))# 生成更新SQLattrs['__update__'] = 'update `%s` set %s where `%s`=?' % (tableName, ', '.join(map(lambda f: '`%s`=?' % (mappings.get(f).name or f), fields)), primaryKey)# 生成删除SQLattrs['__delete__'] = 'delete from `%s` where `%s`=?' % (tableName, primaryKey)# 调用type生成类return type.__new__(cls, name, bases, attrs)# 继承自ModelMetaclass元类、dict的类
class Model(dict, metaclass=ModelMetaclass):def __init__(self, **kw):super(Model, self).__init__(**kw)# 重写get方法def __getattr__(self, key):try:return self[key]except KeyError:raise AttributeError(r"'Model' object has no attribute '%s'" % key)# 重写set方法def __setattr__(self, key, value):self[key] = value# 重写get方法def getValue(self, key):return getattr(self, key, None)# 获取值，当不存在的时候获取的是默认值def getValueOrDefault(self, key):value = getattr(self, key, None)if value is None:field = self.__mappings__[key]if field.default is not None:value = field.default() if callable(field.default) else field.defaultlogging.debug('using default value for %s: %s' % (key, str(value)))setattr(self, key, value)return value@classmethodasync def findAll(cls, where=None, args=None, **kw):' find objects by where clause. '# 获取元类自动生成的SQL语句,并根据当前的参数，继续合成sql = [cls.__select__]if where:sql.append('where')sql.append(where)if args is None:args = []orderBy = kw.get('orderBy', None)if orderBy:sql.append('order by')sql.append(orderBy)limit = kw.get('limit', None)if limit is not None:sql.append('limit')if isinstance(limit, int):sql.append('?')args.append(limit)elif isinstance(limit, tuple) and len(limit) == 2:sql.append('?, ?')args.extend(limit)else:raise ValueError('Invalid limit value: %s' % str(limit))# 直接调用select函数来处理, 这里是等待函数执行完成函数才能返回rs = await select(' '.join(sql), args)# 该类本身是字典，自己用自己生成新的实例，里面的阈值正好也是需要查询return [cls(**r) for r in rs]@classmethodasync def findNumber(cls, selectField, where=None, args=None):' find number by select and where. '# 这里的 _num_ 什么意思？别名？ 我估计是mysql里面一个记录实时查询结果条数的变量sql = ['select %s _num_ from `%s`' % (selectField, cls.__table__)]if where:sql.append('where')sql.append(where)rs = await select(' '.join(sql), args, 1)if len(rs) == 0:return Nonereturn rs[0]['_num_']@classmethodasync def find(cls, pk):' find object by primary key. '# 通过主键查找对象, 如果不存在，那么就返回Noners = await select('%s where `%s`=?' % (cls.__select__, cls.__primary_key__), [pk], 1)if len(rs) == 0:return Nonereturn cls(**rs[0])# 插入语句对应的方法async def save(self):args = list(map(self.getValueOrDefault, self.__fields__))args.append(self.getValueOrDefault(self.__primary_key__))rows = await execute(self.__insert__, args)if rows != 1:logging.warn('failed to insert record: affected rows: %s' % rows)# 更新语句对应的方法async def update(self):args = list(map(self.getValue, self.__fields__))args.append(self.getValue(self.__primary_key__))rows = await execute(self.__update__, args)if rows != 1:logging.warn('failed to update by primary key: affected rows: %s' % rows)# 删除语句对应的方法async def remove(self):args = [self.getValue(self.__primary_key__)]rows = await execute(self.__delete__, args)if rows != 1:logging.warn('failed to remove by primary key: affected rows: %s' % rows)