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websession.py.wml
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## $Id$
## CDSware Web Session utilities, implementing persistence.
## This file is part of the CERN Document Server Software (CDSware).
## Copyright (C) 2002 CERN.
##
## The CDSware is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public License as
## published by the Free Software Foundation; either version 2 of the
## License, or (at your option) any later version.
##
## The CDSware 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
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with CDSware; if not, write to the Free Software Foundation, Inc.,
## 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
"""
Classes necessary for using in CDSware, as a complement of session, which adds persistence to sessions
by using a MySQL table. Consists of the following classes:
- SessionNotInDb: Exception to be raised when a session doesn't exit
- pSession(Session): Specialisation of the class Session which adds persistence to session
- pSessionMapping: Implements only the necessary methods to make it work with the session manager
"""
import cPickle
import time
from dbquery import run_sql
import session
from session import Session
from UserDict import UserDict
class SessionNotInDb(Exception):
"""Exception to be raised when a requested session doesn't exist in the DB
"""
pass
class pSession(Session):
"""Specialisation of the class Session which adds persistence to sessions
by using a MySQL table (it pickles itself into the corresponding row of
the table). The class provides methods to save and retrieve an instance
to/from the DB and to access the main session attributes (uid). The
table in the DB must have the following structure:
session_key - text - unique
uid - int
session_object - blob
Attributes:
__tableName -- (string) name of the table in the DB where the
sessions are going to be stored
__uid -- (int) user identifier who initiated the session
__dirty -- (bool) flag indicating whether the session has been
modified (and therefore needs to be saved back to the DB) or not
"""
__tableName = "session"
__ExpireTime = 1050043127
def __init__( self, request, id, uid=-1 ):
Session.__init__( self, request, id )
self.__uid = uid
self.__dirty = 0
def is_dirty( self ):
return self.__dirty
def getUid( self ):
return self.__uid
def setUid( self, newUid ):
self.__uid = int(newUid)
self.__dirty = 1
def retrieve( cls, sessionId ):
"""method for retrieving a session from the DB for the given id. If the
id has no corresponding session an exception is raised
"""
sql = "select session_object from %s where session_key='%s'"%(cls.__tableName, sessionId)
res = run_sql(sql)
if len(res)==0:
raise SessionNotInDb("Session %s doesn't exist"%sessionId)
s = cPickle.loads( res[0][0] )
return s
retrieve = classmethod( retrieve )
def __getRepr( self ):
return cPickle.dumps( self )
def save( self ):
"""method that tries to insert the session as NEW in the DB. If this
fails (giving an integrity error) it means the session already
exists there and it must be updated, so it performs the
corresponding SQL update
"""
repr = self.__getRepr().replace("'", "\\\'")
repr = repr.replace('"', '\\\"')
try:
sql = 'INSERT INTO %s (session_key, session_expiry, session_object, uid) values ("%s","%s","%s","%s")' % \
(self.__class__.__tableName, self.id, self.get_access_time()+60*60*24*2, repr, int(self.getUid()))
res = run_sql(sql)
# FIXME. WARNING!! it should be "except IntegrityError, e:" but this will
# create a dependency on package MySQL. I'll leave it like this for
# the time being but this can lead to Exception masking
except Exception, e:
sql = 'UPDATE %s SET uid=%s, session_expiry=%s, session_object="%s" WHERE session_key="%s"' % \
(self.__class__.__tableName, int(self.getUid()), self.get_access_time()+60*60*24*2, repr, self.id)
res = run_sql(sql)
self.__dirty=0
class pSessionMapping(UserDict):
"""Only the necessary methods to make it work with the session manager
have been implemented.
"""
def __includeItemFromDB(self, key):
if key not in self.data.keys():
try:
s = pSession.retrieve( key )
self.data[key] = s
except SessionNotInDb, e:
pass
def __setitem__(self, key, v):
"""when a session is added or updated in the dictionary it means it
must be updated within the DB
"""
v.save()
UserDict.__setitem__(self, key, v)
def __getitem__(self, key):
"""in order not to have to load all the sessions in the dictionary
(normally only a single session is needed on each web request) when
a session is requested the object looks to see if it is in the
dictionary (memory) and if not it tries to retrieve it from the
DB, puts it in the dictionary and returns the requested item. If
the session doesn't exist a normal KeyError exception is raised
"""
self.__includeItemFromDB( key )
return UserDict.__getitem__(self, key)
def has_key(self, key):
"""same as for "__getitem__": it checks whether the session exist in the
local dictionary or in the DB.
"""
self.__includeItemFromDB( key )
return UserDict.has_key( self, key )

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