问题描述
我正在尝试使用烧瓶,sqlAlchemy,棉花糖和PostGIS创建API,这些API返回GeoJson FeatureCollection。我希望能够使用任何地理对象(点,多边形,...)。
我尝试了很多事情,但从未成功地重新创建GeoJson FeatureCollection格式。是否可以将形状强制为棉花糖模式?
这是sqlAlchemy模型:
class Locations(db.Model):
__tablename__ = 'locations'
id: int = db.Column(db.Integer,primary_key=True,autoincrement=True)
name: int = db.Column(db.String,nullable=False)
linename: str = db.Column(db.String,nullable=False)
point = db.Column(Geometry('POINT'))
这是我的棉花糖模式,
class LocationsSchema(sqlAlchemyAutoSchema):
point = fields.Method('wkt_to_geojson')
def wkt_to_geojson(self,obj):
return {'type': 'Feature','properties': {'linename': obj.linename},'geometry': shapely.geometry.mapping(to_shape(obj.point))}
class Meta:
model = Locations
locations_schema = LocationsSchema(很多=是,仅= [“点”])
这是我的蓝图路线:
@map_data_blueprint.route('/locations',methods=['GET'])
def all_items():
locations = Locations.query.all()
serialized = locations_schema.dump(locations)
return jsonify(serialized)
这是我从API收到的json:
[
{
"id": 2,"point": {
"geometry": {
"coordinates": [
6.130649,49.609332
],"type": "Point"
},"properties": {
"linename": "1"
},"type": "Feature"
}
},{
"id": 3,"point": {
"geometry": {
"coordinates": [
6.126288,49.598557
],"type": "Feature"
}
}]
但是我尝试获取FeatureCollection Geojson格式,这里是一个示例:https://storage.googleapis.com/mapsdevsite/json/google.json
解决方法
我通过结合geoalchemy2.shape,shapely和geojson包找到了解决方案。我为该特定的API删除了棉花糖层,因为我还没有找到使用棉花糖层的方法。
def parse_geojson(obj):
geo = shapely.geometry.mapping(to_shape(obj.point))
if geo:
return geojson.Feature(
id=obj.id,geometry=geo,properties={
"linename": obj.linename
})
@map_data_blueprint.route('/locations',methods=['GET'])
def all_items():
locations = Locations.query.all()
features = [parse_geojson(location) for location in locations]
serialized = geojson.dumps(geojson.FeatureCollection(features))
return serialized
我不知道在路径中序列化查询答案是否是最佳实践,但这是可行的。