Django-1.2.1/django/contrib/messages/storage/fallback.py

   1 from django.contrib.messages.storage.base import BaseStorage
   2 from django.contrib.messages.storage.cookie import CookieStorage
   3 from django.contrib.messages.storage.session import SessionStorage
   4
   5 class FallbackStorage(BaseStorage):
   6     """
   7     Tries to store all messages in the first backend, storing any unstored
   8     messages in each subsequent backend backend.
   9     """
  10     storage_classes = (CookieStorage, SessionStorage)
  11
  12     def __init__(self, *args, **kwargs):
  13         super(FallbackStorage, self).__init__(*args, **kwargs)
  14         self.storages = [storage_class(*args, **kwargs)
  15                          for storage_class in self.storage_classes]
  16         self._used_storages = set()
  17
  18     def _get(self, *args, **kwargs):
  19         """
  20         Gets a single list of messages from all storage backends.
  21         """
  22         all_messages = []
  23         for storage in self.storages:
  24             messages, all_retrieved = storage._get()
  25             # If the backend hasn't been used, no more retrieval is necessary.
  26             if messages is None:
  27                 break
  28             if messages:
  29                 self._used_storages.add(storage)
  30             all_messages.extend(messages)
  31             # If this storage class contained all the messages, no further
  32             # retrieval is necessary
  33             if all_retrieved:
  34                 break
  35         return all_messages, all_retrieved
  36
  37     def _store(self, messages, response, *args, **kwargs):
  38         """
  39         Stores the messages, returning any unstored messages after trying all
  40         backends.
  41
  42         For each storage backend, any messages not stored are passed on to the
  43         next backend.
  44         """
  45         for storage in self.storages:
  46             if messages:
  47                 messages = storage._store(messages, response,
  48                                           remove_oldest=False)
  49             # Even if there are no more messages, continue iterating to ensure
  50             # storages which contained messages are flushed.
  51             elif storage in self._used_storages:
  52                 storage._store([], response)
  53                 self._used_storages.remove(storage)
  54         return messages