基于Torndb的简易ORM
时间：2014-05-09 13:54:08
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最近在用tornado写一个基于Rest的WebService服务端，只提供后端服务，其他webserver应用通过URL，Rest的方式来访问。
我们在开发web应用的时候，难免会想到ORM的一些框架，比如java ee中常用的hibernate, ibatis以及python中的SQLAlchemy之类。使用ORM会在一定程度上加快我们的开发效率。
一个简易ORM框架主要实现如下几个功能就足够了：
1.插入： 类对象映射为数据库记录
2.查询：数据库记录映射为类对象
3.修改、删除：可以通过自己写sql语句来搞定。
python中有类，同时也有dict字典类型，如果将字典再包装为类，则显得过渡包装了，反倒很不灵活，因此，提炼一下，python的ORM框架只需要实现如下几点就足够：
1.插入： python的dict映射为数据库记录
2.查询：数据库记录映射为python的dict以及list等
3.修改、删除：可以通过自己写sql语句来搞定。
经过一些测试，技术选型，最终确定了使用tornadb，非常轻量级，查询数据库返回的对象直接映射为python的数据类型dict或者list之类。可以用类似java中“对象.属性”的方式来访问数据。这简直是太爽了~首先，看一个小例子。
import types
import time
class Row(dict):
"""A dict that allows for object-like property access syntax."""
def __getattr__(self, name):
try:
return self[name]
except KeyError:
raise AttributeError(name)
dic = Row()
dic.name = ‘hello‘
dic.num = ‘12334‘
print type(dic)
print "dic.name: " + dic.name
print "dic.num: " + dic.num输出结果为：
<class ‘__main__.Row‘>
dic.name: hello
dic.num: 12334
dic.name: hello
dic.num: 12334
通过这个例子，我们可以看到，python里面的dict类型，是可以变成类似java中“对象.属性”的方式来访问的。
torndb就是通过这样的方式，查询返回的数据可以通过“.列名”来直接访问。
查询的时候直接返回dict或者list类型，那插入呢？如果可以像java一样，传入一个对象，通过ORM框架直接反射为sql操作，这样多方便啊~
还是dict，如果我们插入的时候，直接将插入的数据格式保存为dict，通过这个dict生成insert语句就可以了，经过查阅各种资料，我提炼出来了如下方法：（使用的时候直接将该方法放入torndb.py中即可）
def insert_by_dict(self, tablename, rowdict, replace=False):
cursor = self._cursor()
cursor.execute("describe %s" % tablename)
allowed_keys = set(row[0] for row in cursor.fetchall())
keys = allowed_keys.intersection(rowdict)
if len(rowdict) > len(keys):
unknown_keys = set(rowdict) - allowed_keys
logging.error("skipping keys: %s", ", ".join(unknown_keys))
columns = ", ".join(keys)
values_template = ", ".join(["%s"] * len(keys))
if replace:
sql = "REPLACE INTO %s (%s) VALUES (%s)" % (
tablename, columns, values_template)
else:
sql = "INSERT INTO %s (%s) VALUES (%s)" % (
tablename, columns, values_template)
values = tuple(rowdict[key] for key in keys)
try:
cursor.execute(sql, values)
#self._execute(cursor, sql, values, None)
return cursor.lastrowid
finally:
cursor.close()这样，插入的时候我们就再也不用写繁琐的sql语句了，只需要将我们要插入的对象使用dict封装，比如：
有个host表，里面有hostname，ip两个字段，则我们可以用如下几行代码，就可以插入到数据库：
host = {}
host[‘hostname‘] = ‘test1‘
host[‘ip‘] = ‘10.22.10.90‘
ret = db.insert_by_dict("Host", host)是不是很方便呢？：）下面是我修改过后，完整的torndb源码。欢迎大家多多下载使用。
#!/usr/bin/env python
#
# Copyright 2009 Facebook
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""A lightweight wrapper around MySQLdb.
Originally part of the Tornado framework. The tornado.database module
is slated for removal in Tornado 3.0, and it is now available separately
as torndb.
"""
from __future__ import absolute_import, division, with_statement
import copy
import itertools
import logging
import os
import time
try:
import MySQLdb.constants
import MySQLdb.converters
import MySQLdb.cursors
except ImportError:
# If MySQLdb isn‘t available this module won‘t actually be useable,
# but we want it to at least be importable on readthedocs.org,
# which has limitations on third-party modules.
if ‘READTHEDOCS‘ in os.environ:
MySQLdb = None
else:
raise
version = "0.2"
version_info = (0, 2, 0, 0)
class Connection(object):
"""A lightweight wrapper around MySQLdb DB-API connections.
The main value we provide is wrapping rows in a dict/object so that
columns can be accessed by name. Typical usage::
db = torndb.Connection("localhost", "mydatabase")
for article in db.query("SELECT * FROM articles"):
print article.title
Cursors are hidden by the implementation, but other than that, the methods
are very similar to the DB-API.
We explicitly set the timezone to UTC and assume the character encoding to
UTF-8 (can be changed) on all connections to avoid time zone and encoding errors.
The sql_mode parameter is set by default to "traditional", which "gives an error instead of a warning"
(http://dev.mysql.com/doc/refman/5.0/en/server-sql-mode.html). However, it can be set to
any other mode including blank (None) thereby explicitly clearing the SQL mode.
"""
def __init__(self, host, database, user=None, password=None,
max_idle_time=7 * 3600, connect_timeout=0,
time_zone="+0:00", charset = "utf8", sql_mode="TRADITIONAL"):
self.host = host
self.database = database
self.max_idle_time = float(max_idle_time)
args = dict(conv=CONVERSIONS, use_unicode=True, charset=charset,
db=database, init_command=(‘SET time_zone = "%s"‘ % time_zone),
connect_timeout=connect_timeout, sql_mode=sql_mode)
if user is not None:
args["user"] = user
if password is not None:
args["passwd"] = password
# We accept a path to a MySQL socket file or a host(:port) string
if "/" in host:
args["unix_socket"] = host
else:
self.socket = None
pair = host.split(":")
if len(pair) == 2:
args["host"] = pair[0]
args["port"] = int(pair[1])
else:
args["host"] = host
args["port"] = 3306
self._db = None
self._db_args = args
self._last_use_time = time.time()
try:
self.reconnect()
except Exception:
logging.error("Cannot connect to MySQL on %s", self.host,
exc_info=True)
def __del__(self):
self.close()
def close(self):
"""Closes this database connection."""
if getattr(self, "_db", None) is not None:
self._db.close()
self._db = None
def reconnect(self):
"""Closes the existing database connection and re-opens it."""
self.close()
self._db = MySQLdb.connect(**self._db_args)
self._db.autocommit(True)
def initClientEncode(self):
"""mysql client encoding=utf8"""
curs = self._cursor()
curs.execute("SET NAMES utf8")
return curs
def iter(self, query, *parameters, **kwparameters):
"""Returns an iterator for the given query and parameters."""
self._ensure_connected()
cursor = MySQLdb.cursors.SSCursor(self._db)
try:
self._execute(cursor, query, parameters, kwparameters)
column_names = [d[0] for d in cursor.description]
for row in cursor:
yield Row(zip(column_names, row))
finally:
cursor.close()
def query(self, query, *parameters, **kwparameters):
"""Returns a row list for the given query and parameters."""
cursor = self._cursor()
try:
self._execute(cursor, query, parameters, kwparameters)
column_names = [d[0] for d in cursor.description]
return [Row(itertools.izip(column_names, row)) for row in cursor]
finally:
cursor.close()
def get(self, query, *parameters, **kwparameters):
"""Returns the (singular) row returned by the given query.
If the query has no results, returns None. If it has
more than one result, raises an exception.
"""
rows = self.query(query, *parameters, **kwparameters)
if not rows:
return None
elif len(rows) > 1:
raise Exception("Multiple rows returned for Database.get() query")
else:
return rows[0]
# rowcount is a more reasonable default return value than lastrowid,
# but for historical compatibility execute() must return lastrowid.
def execute(self, query, *parameters, **kwparameters):
"""Executes the given query, returning the lastrowid from the query."""
return self.execute_lastrowid(query, *parameters, **kwparameters)
def execute_lastrowid(self, query, *parameters, **kwparameters):
"""Executes the given query, returning the lastrowid from the query."""
cursor = self._cursor()
try:
self._execute(cursor, query, parameters, kwparameters)
return cursor.lastrowid
finally:
cursor.close()
def execute_rowcount(self, query, *parameters, **kwparameters):
"""Executes the given query, returning the rowcount from the query."""
cursor = self._cursor()
try:
self._execute(cursor, query, parameters, kwparameters)
return cursor.rowcount
finally:
cursor.close()
def executemany(self, query, parameters):
"""Executes the given query against all the given param sequences.
We return the lastrowid from the query.
"""
return self.executemany_lastrowid(query, parameters)
def executemany_lastrowid(self, query, parameters):
"""Executes the given query against all the given param sequences.
We return the lastrowid from the query.
"""
cursor = self._cursor()
try:
cursor.executemany(query, parameters)
return cursor.lastrowid
finally:
cursor.close()
def get_fields_str(self, tablename):
cursor = self._cursor()
cursor.execute("describe %s" % tablename)
fields=[]
for row in cursor.fetchall():
fields.append(row[0])
str = ", ".join(fields)
cursor.close()
return str
def get_fields_prefix_str(self, tablename, prefix):
cursor = self._cursor()
cursor.execute("describe %s" % tablename)
fields=[]
for row in cursor.fetchall():
fields.append(prefix+row[0])
str = ", ".join(fields)
cursor.close()
return str
def get_select_sql(self, tablename):
str = self.get_fields_str(tablename)
sql = "SELECT " + str + " FROM " + tablename + " "
return sql
def insert_by_dict(self, tablename, rowdict, replace=False):
cursor = self._cursor()
cursor.execute("describe %s" % tablename)
allowed_keys = set(row[0] for row in cursor.fetchall())
keys = allowed_keys.intersection(rowdict)
if len(rowdict) > len(keys):
unknown_keys = set(rowdict) - allowed_keys
logging.error("skipping keys: %s", ", ".join(unknown_keys))
columns = ", ".join(keys)
values_template = ", ".join(["%s"] * len(keys))
if replace:
sql = "REPLACE INTO %s (%s) VALUES (%s)" % (
tablename, columns, values_template)
else:
sql = "INSERT INTO %s (%s) VALUES (%s)" % (
tablename, columns, values_template)
values = tuple(rowdict[key] for key in keys)
try:
cursor.execute(sql, values)
#self._execute(cursor, sql, values, None)
return cursor.lastrowid
finally:
cursor.close()
def transaction(self, query, *parameters, **kwparameters):
self._db.begin()
cursor = self._cursor()
status = True
try:
for sql in query:
cursor.execute(sql, kwparameters or parameters)
self._db.commit()
except OperationalError, e:
self._db.rollback()
status = False
raise Exception(e.args[1], e.args[0])
finally:
cursor.close()
return status
def executemany_rowcount(self, query, parameters):
"""Executes the given query against all the given param sequences.
We return the rowcount from the query.
"""
cursor = self._cursor()
try:
cursor.executemany(query, parameters)
return cursor.rowcount
finally:
cursor.close()
update = execute_rowcount
updatemany = executemany_rowcount
insert = execute_lastrowid
insertmany = executemany_lastrowid
def _ensure_connected(self):
# Mysql by default closes client connections that are idle for
# 8 hours, but the client library does not report this fact until
# you try to perform a query and it fails. Protect against this
# case by preemptively closing and reopening the connection
# if it has been idle for too long (7 hours by default).
if (self._db is None or
(time.time() - self._last_use_time > self.max_idle_time)):
self.reconnect()
self._last_use_time = time.time()
def _cursor(self):
self._ensure_connected()
return self._db.cursor()
def _execute(self, cursor, query, parameters, kwparameters):
try:
return cursor.execute(query, kwparameters or parameters)
except OperationalError:
logging.error("Error connecting to MySQL on %s", self.host)
self.close()
raise
class Row(dict):
"""A dict that allows for object-like property access syntax."""
def __getattr__(self, name):
try:
return self[name]
except KeyError:
raise AttributeError(name)
if MySQLdb is not None:
# Fix the access conversions to properly recognize unicode/binary
FIELD_TYPE = MySQLdb.constants.FIELD_TYPE
FLAG = MySQLdb.constants.FLAG
CONVERSIONS = copy.copy(MySQLdb.converters.conversions)
field_types = [FIELD_TYPE.BLOB, FIELD_TYPE.STRING, FIELD_TYPE.VAR_STRING]
if ‘VARCHAR‘ in vars(FIELD_TYPE):
field_types.append(FIELD_TYPE.VARCHAR)
for field_type in field_types:
CONVERSIONS[field_type] = [(FLAG.BINARY, str)] + CONVERSIONS[field_type]
# Alias some common MySQL exceptions
IntegrityError = MySQLdb.IntegrityError
OperationalError = MySQLdb.OperationalError
外带一个小例子,完整版请参照我在github上发布的一个webservice框架：https://github.com/yunfeiflying/tornado-rest-web-service-framwork/
#!/usr/bin/env python2.7
#
# -*- coding:utf-8 -*-
#
# Author : YunJianFei
# E-mail : yunjianfei@126.com
# Date : 2014/02/25
# Desc : Test db
#
""" Data Access Object
This file impelements DBI for the table ‘Host‘
The Host table‘s create sql is :
CREATE TABLE IF NOT EXISTS `test`.`Host` (
`host_id` INT NOT NULL AUTO_INCREMENT,
`host_type` INT NULL,
`hostname` VARCHAR(45) NULL,
`ip` VARCHAR(45) NULL,
`create_time` VARCHAR(45) NULL,
`cpu_count` INT NULL,
`cpu_pcount` INT NULL,
`memory` INT NULL,
`os` VARCHAR(200) NULL,
`comment` VARCHAR(200) NULL,
PRIMARY KEY (`host_id`))
ENGINE = InnoDB;
"""
from util.dbconst import TableName, TableFields, TableSelectSql
import logging
class HostDao:
def __init__(self, db):
mysql_host = "192.168.10.11:3306"
db_name = "test"
db_user = "root"
db_pass = ""
self.db = torndb.Connection(
host=mysql_host, database=db_name,
user=db_user, password=db_pass
)
def insert_by_dict(self, host, replace=False):
try:
id = self.db.insert_by_dict("Host", host, replace)
return id
except Exception, ex:
logging.error("Insert host failed! Exception: %s Host: %s", str(ex), str(host))
return None
def if_exist(self, hostname, ip):
ret = self.get_by_hostname(hostname)
if ret != None:
return True
ret = self.get_by_ip(ip)
if ret != None:
return True
return False
def get_by_ip(self, ip):
sql = TableSelectSql.HOST + " where ip=‘" + str(ip)+"‘"
return self.db.get(sql)
def get_all(self):
sql = TableSelectSql.HOST
return self.db.query(sql)
def get_by_hostname(self, hostname):
sql = TableSelectSql.HOST + " where hostname=‘" + str(hostname)+"‘"
return self.db.get(sql)
def get_by_id(self, host_id):
sql = TableSelectSql.HOST + " where host_id=%s" % str(host_id)
return self.db.get(sql)
def get_id_by_hostname(self, hostname):
sql = TableSelectSql.HOST + " where hostname=‘" + str(hostname)+"‘"
ret = self.db.get(sql)
if ret != None:
return ret.host_id
return None
def update_worker_num_by_hostname(self, hostname, worker_num):
try:
sql = "UPDATE Host SET worker_num=%s WHERE hostname=‘%s‘" % (worker_num, str(hostname))
ret = self.db.execute(sql)
return ret
except Exception, ex:
logging.error("Update Host failed! Exception: %s hostname: %s , worker_num: %s", str(ex), str(hostname), worker_num)
return None
def update_worker_num_by_id(self, host_id, worker_num):
try:
sql = "UPDATE Host SET worker_num=%s WHERE host_id=%s" % (worker_num, host_id)
ret = self.db.execute(sql)
return ret
except Exception, ex:
logging.error("Update Host failed! Exception: %s host_id: %s , worker_num: %s", str(ex), host_id, worker_num)
return None
def del_by_hostname(self, hostname):
try:
sql = "DELETE FROM Host WHERE hostname=‘" + str(hostname) + "‘"
ret = self.db.execute(sql)
return ret
except Exception, ex:
logging.error("Delete host failed! Exception: %s hostname: %s", str(ex), str(hostname))
return None
def del_by_id(self, host_id):
try:
sql = "DELETE FROM Host WHERE host_id=" + str(host_id)
ret = self.db.execute(sql)
return ret
except Exception, ex:
logging.error("Delete host failed! Exception: %s host_id: %s", str(ex), host_id)
return None
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