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