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- from __future__ import unicode_literals
-
- from django.contrib.gis.gdal import HAS_GDAL
- from django.core.serializers.base import (
- SerializationError, SerializerDoesNotExist,
- )
- from django.core.serializers.json import Serializer as JSONSerializer
-
- if HAS_GDAL:
- from django.contrib.gis.gdal import CoordTransform, SpatialReference
-
-
- class Serializer(JSONSerializer):
- """
- Convert a queryset to GeoJSON, http://geojson.org/
- """
- def _init_options(self):
- super(Serializer, self)._init_options()
- self.geometry_field = self.json_kwargs.pop('geometry_field', None)
- self.srid = self.json_kwargs.pop('srid', 4326)
- if (self.selected_fields is not None and self.geometry_field is not None
- and self.geometry_field not in self.selected_fields):
- self.selected_fields = list(self.selected_fields) + [self.geometry_field]
-
- def start_serialization(self):
- self._init_options()
- self._cts = {} # cache of CoordTransform's
- self.stream.write(
- '{"type": "FeatureCollection", "crs": {"type": "name", "properties": {"name": "EPSG:%d"}},'
- ' "features": [' % self.srid)
-
- def end_serialization(self):
- self.stream.write(']}')
-
- def start_object(self, obj):
- super(Serializer, self).start_object(obj)
- self._geometry = None
- if self.geometry_field is None:
- # Find the first declared geometry field
- for field in obj._meta.fields:
- if hasattr(field, 'geom_type'):
- self.geometry_field = field.name
- break
-
- def get_dump_object(self, obj):
- data = {
- "type": "Feature",
- "properties": self._current,
- }
- if self._geometry:
- if self._geometry.srid != self.srid:
- # If needed, transform the geometry in the srid of the global geojson srid
- if not HAS_GDAL:
- raise SerializationError(
- 'Unable to convert geometry to SRID %s when GDAL is not installed.' % self.srid
- )
- if self._geometry.srid not in self._cts:
- srs = SpatialReference(self.srid)
- self._cts[self._geometry.srid] = CoordTransform(self._geometry.srs, srs)
- self._geometry.transform(self._cts[self._geometry.srid])
- data["geometry"] = eval(self._geometry.geojson)
- else:
- data["geometry"] = None
- return data
-
- def handle_field(self, obj, field):
- if field.name == self.geometry_field:
- self._geometry = field.value_from_object(obj)
- else:
- super(Serializer, self).handle_field(obj, field)
-
-
- class Deserializer(object):
- def __init__(self, *args, **kwargs):
- raise SerializerDoesNotExist("geojson is a serialization-only serializer")
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