我一直在使用Geo Django GeoJSON序列化程序,这样我就可以从PostGIS数据库中检索一些对象,并将它们显示在OpenLayers地图上。
我以以下方式获取要显示的对象:
gqs = self.model.objects.filter(point__distance_lte=(pnt, long(dist)))
type(gqs)
<class 'django.contrib.gis.db.models.query.GeoQuerySet'>
地理对象包括预期的所有模型字段:
self.model._meta.get_fields()
(<django.db.models.fields.AutoField: id>,
<django.db.models.fields.CharField: name>,
<django.db.models.fields.SlugField: name_slug>,
<django.db.models.fields.CharField: contact>,
<django.db.models.fields.CharField: address>,
<django.db.models.fields.CharField: postcode>,
<django.db.models.fields.EmailField: email>,
<django.db.models.fields.CharField: fax>,
<django.db.models.fields.CharField: tel>,
<django.db.models.fields.CharField: tel1>,
<django.db.models.fields.CharField: tel_fax>,
<django.db.models.fields.URLField: url>,
<django.db.models.fields.CharField: wardlabel>,
<django.db.models.fields.DecimalField: lon>,
<django.db.models.fields.DecimalField: lat>,
<django.db.models.fields.IntegerField: easting>,
<django.db.models.fields.IntegerField: northing>,
<django.db.models.fields.DateField: first_entered>,
<django.db.models.fields.DateField: updated>,
<django.contrib.gis.db.models.fields.PointField: point>)
包括id值。。。
(Pdb) gqs[0].id
5
然后,我以最简单的方式将GeoQuerySet传递给GeoJSON序列化程序:
gqs_serialized = serialize('geojson', gqs)
并获得输出:
gqs_serialized
u'{"type": "FeatureCollection",
"crs": {
"type": "name",
"properties": {"name": "EPSG:4326"}},
"features": [
{"geometry": {"type": "Point", "coordinates": [-0.19038, 51.490657]}, "type": "Feature",
"properties": {
"tel1": null,
"fax": null,
"tel": null,
"name": "some club",
"url": null,
"wardlabel": "Redcliffe",
"lon": "-0.190380",
"updated": null,
"first_entered": "2013-12-01",
"contact": "some name",
"name_slug": "some club slug",
"postcode": "SW5 0JE",
"easting": 525732,
"address": "Some Address, London",
"lat": "51.490657",
"tel_fax": null,
"email": null,
"northing": 178409}},
{"geometry": {"type": "Point", "coordinates": [-0.137183, 51.495597]}, "type": "Feature",
"properties": { etc...
除了模型中的"id"字段(AutoField)之外,所有内容都存在。我想在网页中使用id值作为div id值,并且我真的不想在我认为应该已经有一个唯一的id时创建另一个唯一id(即组合lon/lat值)。
丢失的"id"字段怎么了?
只要输出必须与规范兼容,股票序列化程序就会省略不支持的字段。然而,您可以创建自己的序列化程序:
# yourapp/geojson_serializer.py
from django.contrib.gis.serializers import Serializer as GeoJSONSerializer
class Serializer(GeoJSONSerializer):
def get_dump_object(self, obj):
data = super(Serializer, self).get_dump_object(obj)
# Extend to your taste
data.update(id=obj.pk)
return data
在settings.py
:中启用新的序列化程序
SERIALIZATION_MODULES = {
"custom_geojson": "yourapp.geojson_serializer",
}
然后在你的代码中使用它:
from django.core import serializers
data = serializers.serialize('custom_geojson', some_model)
我也能够通过使用@jayuu的输入来解决这个问题。面向新读者对这个问题感兴趣我发布了完整的解决方案:
#myapp/geojson_serializer.py
from django.core import serializers
GeoJSONSerializer = serializers.get_serializer("geojson")
class Serializer(GeoJSONSerializer):
def get_dump_object(self, obj):
data = super(Serializer, self).get_dump_object(obj)
# Extend to your taste
data.update(id=obj.pk)
return data
然后,为了在我的视图中使用它,我只是导入了该函数,因为我对注册我的序列化程序没有兴趣
#myapp/views.py
from .geojson_serializer import Serializer
def MapDataView(request):
geojson_serializer = Serializer()
geojson_serializer.serialize(some_queryset)
data = geojson_serializer.getvalue()
return HttpResponse(data, content_type='json')
就在这里。
我解决这个问题的一种方法是要求它序列化"pk"字段,这正如预期的那样。
gqs_serialized = serialize('geojson', gqs, fields=('pk', ))