#!/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, logging
import 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SQL
await 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 = name
self.column_type = column_type
self.primary_key = primary_key
self.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 name
logging.info('found model: %s (table: %s)' % (name, tableName))
# 创建映射字典
mappings = dict()
# 域list
fields = []
# 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] = v
if 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 = k
else:
# 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SQL
attrs['__select__'] = 'select `%s`, %s from `%s`' % (primaryKey, ', '.join(escaped_fields), tableName)
# 生成插入SQL
attrs['__insert__'] = 'insert into `%s` (%s, `%s`) values (%s)' % (tableName, ', '.join(escaped_fields), primaryKey, create_args_string(len(escaped_fields) + 1))
# 生成更新SQL
attrs['__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SQL
attrs['__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.default
logging.debug('using default value for %s: %s' % (key, str(value)))
setattr(self, key, value)
return value
@classmethod
async 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]
@classmethod
async 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 None
return rs[0]['_num_']
@classmethod
async 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None
rs = await select('%s where `%s`=?' % (cls.__select__, cls.__primary_key__), [pk], 1)
if len(rs) == 0:
return None
return 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)
