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"""
XML serializer.
"""
from django.conf import settings
from django.core.serializers import base
from django.db import models
from django.utils.xmlutils import SimplerXMLGenerator
from xml.dom import pulldom
class Serializer(base.Serializer):
"""
Serializes a QuerySet to XML.
"""
def start_serialization(self):
"""
Start serialization -- open the XML document and the root element.
"""
self.xml = SimplerXMLGenerator(self.stream, self.options.get("encoding", settings.DEFAULT_CHARSET))
self.xml.startDocument()
self.xml.startElement("django-objects", {"version" : "1.0"})
def end_serialization(self):
"""
End serialization -- end the document.
"""
self.xml.endElement("django-objects")
self.xml.endDocument()
def start_object(self, obj):
"""
Called as each object is handled.
"""
if not hasattr(obj, "_meta"):
raise base.SerializationError("Non-model object (%s) encountered during serialization" % type(obj))
self.xml.startElement("object", {
"pk" : str(obj._get_pk_val()),
"model" : str(obj._meta),
})
def end_object(self, obj):
"""
Called after handling all fields for an object.
"""
self.xml.endElement("object")
def handle_field(self, obj, field):
"""
Called to handle each field on an object (except for ForeignKeys and
ManyToManyFields)
"""
self.xml.startElement("field", {
"name" : field.name,
"type" : field.get_internal_type()
})
# Get a "string version" of the object's data (this is handled by the
# serializer base class).
if getattr(obj, field.name) is not None:
value = self.get_string_value(obj, field)
self.xml.characters(str(value))
else:
self.xml.addQuickElement("None")
self.xml.endElement("field")
def handle_fk_field(self, obj, field):
"""
Called to handle a ForeignKey (we need to treat them slightly
differently from regular fields).
"""
self._start_relational_field(field)
related = getattr(obj, field.name)
if related is not None:
self.xml.characters(str(related._get_pk_val()))
else:
self.xml.addQuickElement("None")
self.xml.endElement("field")
def handle_m2m_field(self, obj, field):
"""
Called to handle a ManyToManyField. Related objects are only
serialized as references to the object's PK (i.e. the related *data*
is not dumped, just the relation).
"""
self._start_relational_field(field)
for relobj in getattr(obj, field.name).iterator():
self.xml.addQuickElement("object", attrs={"pk" : str(relobj._get_pk_val())})
self.xml.endElement("field")
def _start_relational_field(self, field):
"""
Helper to output the <field> element for relational fields
"""
self.xml.startElement("field", {
"name" : field.name,
"rel" : field.rel.__class__.__name__,
"to" : str(field.rel.to._meta),
})
class Deserializer(base.Deserializer):
"""
Deserialize XML.
"""
def __init__(self, stream_or_string, **options):
super(Deserializer, self).__init__(stream_or_string, **options)
self.encoding = self.options.get("encoding", settings.DEFAULT_CHARSET)
self.event_stream = pulldom.parse(self.stream)
def next(self):
for event, node in self.event_stream:
if event == "START_ELEMENT" and node.nodeName == "object":
self.event_stream.expandNode(node)
return self._handle_object(node)
raise StopIteration
def _handle_object(self, node):
"""
Convert an <object> node to a DeserializedObject.
"""
# Look up the model using the model loading mechanism. If this fails, bail.
Model = self._get_model_from_node(node, "model")
# Start building a data dictionary from the object. If the node is
# missing the pk attribute, bail.
pk = node.getAttribute("pk")
if not pk:
raise base.DeserializationError("<object> node is missing the 'pk' attribute")
data = {Model._meta.pk.attname : Model._meta.pk.to_python(pk)}
# Also start building a dict of m2m data (this is saved as
# {m2m_accessor_attribute : [list_of_related_objects]})
m2m_data = {}
# Deseralize each field.
for field_node in node.getElementsByTagName("field"):
# If the field is missing the name attribute, bail (are you
# sensing a pattern here?)
field_name = field_node.getAttribute("name")
if not field_name:
raise base.DeserializationError("<field> node is missing the 'name' attribute")
# Get the field from the Model. This will raise a
# FieldDoesNotExist if, well, the field doesn't exist, which will
# be propagated correctly.
field = Model._meta.get_field(field_name)
# As is usually the case, relation fields get the special treatment.
if field.rel and isinstance(field.rel, models.ManyToManyRel):
m2m_data[field.name] = self._handle_m2m_field_node(field_node, field)
elif field.rel and isinstance(field.rel, models.ManyToOneRel):
data[field.attname] = self._handle_fk_field_node(field_node, field)
else:
if len(field_node.childNodes) == 1 and field_node.childNodes[0].nodeName == 'None':
value = None
else:
value = field.to_python(getInnerText(field_node).strip().encode(self.encoding))
data[field.name] = value
# Return a DeserializedObject so that the m2m data has a place to live.
return base.DeserializedObject(Model(**data), m2m_data)
def _handle_fk_field_node(self, node, field):
"""
Handle a <field> node for a ForeignKey
"""
# Check if there is a child node named 'None', returning None if so.
if len(node.childNodes) == 1 and node.childNodes[0].nodeName == 'None':
return None
else:
return field.rel.to._meta.pk.to_python(
getInnerText(node).strip().encode(self.encoding))
def _handle_m2m_field_node(self, node, field):
"""
Handle a <field> node for a ManyToManyField
"""
return [field.rel.to._meta.pk.to_python(
c.getAttribute("pk").encode(self.encoding))
for c in node.getElementsByTagName("object")]
def _get_model_from_node(self, node, attr):
"""
Helper to look up a model from a <object model=...> or a <field
rel=... to=...> node.
"""
model_identifier = node.getAttribute(attr)
if not model_identifier:
raise base.DeserializationError(
"<%s> node is missing the required '%s' attribute" \
% (node.nodeName, attr))
try:
Model = models.get_model(*model_identifier.split("."))
except TypeError:
Model = None
if Model is None:
raise base.DeserializationError(
"<%s> node has invalid model identifier: '%s'" % \
(node.nodeName, model_identifier))
return Model
def getInnerText(node):
"""
Get all the inner text of a DOM node (recursively).
"""
# inspired by http://mail.python.org/pipermail/xml-sig/2005-March/011022.html
inner_text = []
for child in node.childNodes:
if child.nodeType == child.TEXT_NODE or child.nodeType == child.CDATA_SECTION_NODE:
inner_text.append(child.data)
elif child.nodeType == child.ELEMENT_NODE:
inner_text.extend(getInnerText(child))
else:
pass
return "".join(inner_text)
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