Argument store added to updateEntityProperties.
This argument determines if an entity should be stored in the data model after its properties are updated.
It may be useful, for example, along with tasks (Task Queue API). One may want to make some modifications to an entity during execution of a task, but the developer is sure that at least one new task, which also wants to modify the entity, will be queued, so he or she can just update the entity without saving the changes to the data model, set the entity in memcache and the following task (which is to be executed very shortly) is to retrive the current entity from the memcache (without any expensive calls to the actual data model).
==========================
Serializing Django objects
==========================
.. note::
This API is currently under heavy development and may change --
perhaps drastically -- in the future.
You have been warned.
Django's serialization framework provides a mechanism for "translating" Django
objects into other formats. Usually these other formats will be text-based and
used for sending Django objects over a wire, but it's possible for a
serializer to handle any format (text-based or not).
Serializing data
----------------
At the highest level, serializing data is a very simple operation::
from django.core import serializers
data = serializers.serialize("xml", SomeModel.objects.all())
The arguments to the ``serialize`` function are the format to serialize the
data to (see `Serialization formats`_) and a QuerySet_ to serialize.
(Actually, the second argument can be any iterator that yields Django objects,
but it'll almost always be a QuerySet).
.. _QuerySet: ../db_api/#retrieving-objects
You can also use a serializer object directly::
XMLSerializer = serializers.get_serializer("xml")
xml_serializer = XMLSerializer()
xml_serializer.serialize(queryset)
data = xml_serializer.getvalue()
This is useful if you want to serialize data directly to a file-like object
(which includes a HTTPResponse_)::
out = open("file.xml", "w")
xml_serializer.serialize(SomeModel.objects.all(), stream=out)
.. _HTTPResponse: ../request_response/#httpresponse-objects
Deserializing data
------------------
Deserializing data is also a fairly simple operation::
for obj in serializers.deserialize("xml", data):
do_something_with(obj)
As you can see, the ``deserialize`` function takes the same format argument as
``serialize``, a string or stream of data, and returns an iterator.
However, here it gets slightly complicated. The objects returned by the
``deserialize`` iterator *aren't* simple Django objects. Instead, they are
special ``DeserializedObject`` instances that wrap a created -- but unsaved --
object and any associated relationship data.
Calling ``DeserializedObject.save()`` saves the object to the database.
This ensures that deserializing is a non-destructive operation even if the
data in your serialized representation doesn't match what's currently in the
database. Usually, working with these ``DeserializedObject`` instances looks
something like::
for deserialized_object in serializers.deserialize("xml", data):
if object_should_be_saved(deserialized_object):
obj.save()
In other words, the usual use is to examine the deserialized objects to make
sure that they are "appropriate" for saving before doing so. Of course, if you trust your data source you could just save the object and move on.
The Django object itself can be inspected as ``deserialized_object.object``.
Serialization formats
---------------------
Django "ships" with a few included serializers:
========== ==============================================================
Identifier Information
========== ==============================================================
``xml`` Serializes to and from a simple XML dialect.
``json`` Serializes to and from JSON_ (using a version of simplejson_
bundled with Django).
``python`` Translates to and from "simple" Python objects (lists, dicts,
strings, etc.). Not really all that useful on its own, but
used as a base for other serializers.
========== ==============================================================
.. _json: http://json.org/
.. _simplejson: http://undefined.org/python/#simplejson
Notes for specific serialization formats
----------------------------------------
json
~~~~
If you're using UTF-8 (or any other non-ASCII encoding) data with the JSON
serializer, you must pass ``ensure_ascii=False`` as a parameter to the
``serialize()`` call. Otherwise, the output won't be encoded correctly.
For example::
json_serializer = serializers.get_serializer("json")
json_serializer.serialize(queryset, ensure_ascii=False, stream=response)
Writing custom serializers
``````````````````````````
XXX ...