# -*- coding: utf-8 -*-
# Time-stamp: < txaop.py (2016-02-14 12:26) >
# Copyright (C) 2009-2016 Martin Slouf <martin.slouf@sourceforge.net>
#
# This file is a part of Summer.
#
# Summer is free software; you can redistribute it and/or modify it under
# the terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 3 of the License, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""Declarative transaction management."""
import logging
import types
from sqlalchemy.orm import Session
from .aop import AroundMethodAdvice, Proxy
from .tx import TransactionCallback, TransactionWrapper
from .sf import SessionFactory
logger = logging.getLogger(__name__)
[docs]def transactional(func: types.FunctionType):
"""Method decorator marking method as transactional.
Use together with :py:class:`TransactionAdvice` and
:py:class:`TransactionalProxy`.
Methods decorated with :py:func:`transactional` can be run within a
transaction if wrapped in :py:class:`TransactionalProxy`.
Usually it is required to access *SQLAlchemy* session from within the
transaction. Encouraged access to current thread-bound *SQLAlchemy*
session is through :py:class:`summer.sf.SessionFactory`.
Preferred way to manipulate your persistent entities is through *DAO*
objects (:py:mod:`summer.dao`). Intended use case for this decorator
is to mark such :py:class:`summer.dao.EntityDao` methods and then
access current *SQLAlchemy* session by using
:py:attr:`summer.dao.Dao.session` from within the *DAO* method. Thus
you can access *SQLAlchemy* session (and manipulate data), and still
have the transaction boundaries defined on top of your business
methods.
Args:
func (types.FunctionType): function to be decorated
"""
func.transactional = True
# mame .. method name
# mame = "%s.%s" % (func.im_class.__name__, func.__name__)
mame = func.__name__
logger.debug("method %s decorated as transactional", mame)
return func
[docs]class TransactionAdvice(AroundMethodAdvice):
"""Together with :py:func:`transactional` decorator forms a *transaction
aspect*. Advice gets invoked if method is marked with
:py:func:`transactional` and if object is wrapped in
:py:class:`TransactionProxy`.
"""
class Callback(TransactionCallback):
def __init__(self, advice):
"""Creates internal :py:class:`TransactionCallback` instance.
Args:
advice (TransactionAdvice): reference to parent
:py:class:`TransactionAdvice`
"""
TransactionCallback.__init__(self)
self.advice = advice
def txrun(self, session: Session, *args, **kwargs):
result = self.advice.method(*args, **kwargs)
return result
[docs] def __init__(self, method: types.MethodType,
session_factory: SessionFactory):
"""Creates :py:class:`TransactionAdvice` instance.
Args:
method (types.MethodType): instance method marked by
:py:func:`transactional` decorator
session_factory (SessionFactory): session factory to be used
"""
AroundMethodAdvice.__init__(self, method)
self.session_factory = session_factory
[docs] def around(self, *args, **kwargs):
"""Wraps the target method invocation within a transaction. If any
exception is raised it gets re-thrown and the transaction is rolled
back, see :py:class:`summer.tx.TransactionWrapper`.
"""
logger.debug("tx around advice start for '%s'", self.mame)
tx = TransactionWrapper(self.session_factory)
callback = TransactionAdvice.Callback(self)
try:
result = tx.execute(callback, *args, **kwargs)
logger.debug("tx around advice end for '%s'", self.mame)
return result
except Exception as ex:
logger.exception("tx around advice error for '%s'", self.mame)
raise ex
[docs]class TransactionProxy(Proxy):
"""Intercepts method invocations on target object with transaction logic.
It either calls the target object's method directly or invokes the
:py:class:`TransactionAdvice` if the method is marked by
:py:func:`transactional`.
"""
[docs] def __init__(self, target: object, session_factory: SessionFactory=None):
"""Creates the :py:class:`TransactionProxy` instance.
Searches the *target* object for :py:func:`transactional` decorated
methods. It creates a :py:class:`TransactionalAdvice` object for
each method found. Invocation of such a method means invoking a
:py:class:`TransactionalAdvice` object instead, wrapping the call
with transaction.
Args:
target (object): any object that is searched for transactional
methods
session_factory (SessionFactory): session factory to be used;
if ``None``, *target* object
is searched for
``session_factory`` attribute
which is used instead
"""
Proxy.__init__(self, target)
logger.info("creating tx proxy for '%s'", target)
if session_factory is None:
self.session_factory = target.session_factory
else:
self.session_factory = session_factory
methods = self._get_decorated_methods(transactional.__name__)
for i in methods:
advice = TransactionAdvice(i, self.session_factory)
setattr(self, i.__name__, advice)
logger.debug("tx advice '%s' created", advice)