before send to remote

env/lib/python3.8/site-packages/django/contrib/gis/serializers/geojson.py

@@ -0,0 +1,79 @@
+import json
+
+from django.contrib.gis.gdal import CoordTransform, SpatialReference
+from django.core.serializers.base import SerializerDoesNotExist
+from django.core.serializers.json import Serializer as JSONSerializer
+
+
+class Serializer(JSONSerializer):
+    """
+    Convert a queryset to GeoJSON, http://geojson.org/
+    """
+
+    def _init_options(self):
+        super()._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 = [*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().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.selected_fields is None or "pk" in self.selected_fields
+        ) and "pk" not in data["properties"]:
+            data["properties"]["pk"] = obj._meta.pk.value_to_string(obj)
+        if self._geometry:
+            if self._geometry.srid != self.srid:
+                # If needed, transform the geometry in the srid of the global
+                # geojson 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"] = json.loads(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().handle_field(obj, field)
+
+
+class Deserializer:
+    def __init__(self, *args, **kwargs):
+        raise SerializerDoesNotExist("geojson is a serialization-only serializer")