227 lines
7.5 KiB
Python
227 lines
7.5 KiB
Python
"""
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Module for abstract serializer/unserializer base classes.
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"""
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from django.db import models
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from django.utils import six
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class SerializerDoesNotExist(KeyError):
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"""The requested serializer was not found."""
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pass
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class SerializationError(Exception):
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"""Something bad happened during serialization."""
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pass
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class DeserializationError(Exception):
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"""Something bad happened during deserialization."""
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@classmethod
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def WithData(cls, original_exc, model, fk, field_value):
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"""
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Factory method for creating a deserialization error which has a more
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explanatory messsage.
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"""
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return cls("%s: (%s:pk=%s) field_value was '%s'" % (original_exc, model, fk, field_value))
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class ProgressBar(object):
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progress_width = 75
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def __init__(self, output, total_count):
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self.output = output
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self.total_count = total_count
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self.prev_done = 0
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def update(self, count):
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if not self.output:
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return
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perc = count * 100 // self.total_count
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done = perc * self.progress_width // 100
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if self.prev_done >= done:
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return
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self.prev_done = done
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cr = '' if self.total_count == 1 else '\r'
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self.output.write(cr + '[' + '.' * done + ' ' * (self.progress_width - done) + ']')
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if done == self.progress_width:
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self.output.write('\n')
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self.output.flush()
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class Serializer(object):
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"""
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Abstract serializer base class.
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"""
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# Indicates if the implemented serializer is only available for
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# internal Django use.
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internal_use_only = False
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progress_class = ProgressBar
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def serialize(self, queryset, **options):
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"""
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Serialize a queryset.
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"""
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self.options = options
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self.stream = options.pop("stream", six.StringIO())
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self.selected_fields = options.pop("fields", None)
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self.use_natural_foreign_keys = options.pop('use_natural_foreign_keys', False)
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self.use_natural_primary_keys = options.pop('use_natural_primary_keys', False)
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progress_bar = self.progress_class(
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options.pop('progress_output', None), options.pop('object_count', 0)
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)
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self.start_serialization()
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self.first = True
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for count, obj in enumerate(queryset, start=1):
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self.start_object(obj)
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# Use the concrete parent class' _meta instead of the object's _meta
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# This is to avoid local_fields problems for proxy models. Refs #17717.
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concrete_model = obj._meta.concrete_model
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for field in concrete_model._meta.local_fields:
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if field.serialize:
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if field.remote_field is None:
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if self.selected_fields is None or field.attname in self.selected_fields:
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self.handle_field(obj, field)
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else:
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if self.selected_fields is None or field.attname[:-3] in self.selected_fields:
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self.handle_fk_field(obj, field)
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for field in concrete_model._meta.many_to_many:
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if field.serialize:
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if self.selected_fields is None or field.attname in self.selected_fields:
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self.handle_m2m_field(obj, field)
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self.end_object(obj)
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progress_bar.update(count)
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if self.first:
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self.first = False
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self.end_serialization()
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return self.getvalue()
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def start_serialization(self):
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"""
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Called when serializing of the queryset starts.
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"""
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raise NotImplementedError('subclasses of Serializer must provide a start_serialization() method')
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def end_serialization(self):
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"""
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Called when serializing of the queryset ends.
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"""
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pass
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def start_object(self, obj):
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"""
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Called when serializing of an object starts.
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"""
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raise NotImplementedError('subclasses of Serializer must provide a start_object() method')
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def end_object(self, obj):
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"""
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Called when serializing of an object ends.
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"""
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pass
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def handle_field(self, obj, field):
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"""
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Called to handle each individual (non-relational) field on an object.
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"""
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raise NotImplementedError('subclasses of Serializer must provide an handle_field() method')
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def handle_fk_field(self, obj, field):
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"""
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Called to handle a ForeignKey field.
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"""
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raise NotImplementedError('subclasses of Serializer must provide an handle_fk_field() method')
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def handle_m2m_field(self, obj, field):
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"""
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Called to handle a ManyToManyField.
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"""
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raise NotImplementedError('subclasses of Serializer must provide an handle_m2m_field() method')
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def getvalue(self):
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"""
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Return the fully serialized queryset (or None if the output stream is
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not seekable).
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"""
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if callable(getattr(self.stream, 'getvalue', None)):
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return self.stream.getvalue()
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class Deserializer(six.Iterator):
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"""
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Abstract base deserializer class.
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"""
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def __init__(self, stream_or_string, **options):
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"""
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Init this serializer given a stream or a string
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"""
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self.options = options
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if isinstance(stream_or_string, six.string_types):
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self.stream = six.StringIO(stream_or_string)
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else:
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self.stream = stream_or_string
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def __iter__(self):
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return self
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def __next__(self):
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"""Iteration iterface -- return the next item in the stream"""
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raise NotImplementedError('subclasses of Deserializer must provide a __next__() method')
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class DeserializedObject(object):
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"""
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A deserialized model.
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Basically a container for holding the pre-saved deserialized data along
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with the many-to-many data saved with the object.
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Call ``save()`` to save the object (with the many-to-many data) to the
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database; call ``save(save_m2m=False)`` to save just the object fields
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(and not touch the many-to-many stuff.)
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"""
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def __init__(self, obj, m2m_data=None):
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self.object = obj
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self.m2m_data = m2m_data
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def __repr__(self):
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return "<DeserializedObject: %s(pk=%s)>" % (
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self.object._meta.label, self.object.pk)
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def save(self, save_m2m=True, using=None, **kwargs):
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# Call save on the Model baseclass directly. This bypasses any
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# model-defined save. The save is also forced to be raw.
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# raw=True is passed to any pre/post_save signals.
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models.Model.save_base(self.object, using=using, raw=True, **kwargs)
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if self.m2m_data and save_m2m:
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for accessor_name, object_list in self.m2m_data.items():
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getattr(self.object, accessor_name).set(object_list)
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# prevent a second (possibly accidental) call to save() from saving
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# the m2m data twice.
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self.m2m_data = None
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def build_instance(Model, data, db):
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"""
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Build a model instance.
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If the model instance doesn't have a primary key and the model supports
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natural keys, try to retrieve it from the database.
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"""
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obj = Model(**data)
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if (obj.pk is None and hasattr(Model, 'natural_key') and
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hasattr(Model._default_manager, 'get_by_natural_key')):
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natural_key = obj.natural_key()
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try:
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obj.pk = Model._default_manager.db_manager(db).get_by_natural_key(*natural_key).pk
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except Model.DoesNotExist:
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pass
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return obj
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