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几天以来，我想知道如何让我的 Flask 应用程序返回有效的 GeoJSON，这是我目前得到的：

models.py

class Building(base):

    __tablename__ = 'buildings'

    id = Column(Integer, primary_key=True)
    district = Column(Unicode)
    address = Column(Unicode)
    name = Column(Unicode)
    building_type = Column(Unicode)
    mpoly = Column(Geometry('MULTIPOLYGON'))

    building = relationship("User")


# this part is done as answered here: https://stackoverflow.com/questions/41684512/cant-transform-geometry-to-geojson
    def building_to_dict(self):
        return mapping(shapely.wkb.loads(str(self.mpoly), True))
    
    def __str__(self):
        d = dict()
        d["id"] = self.id
        d["district"] = self.district
        d["address"] = self.address
        d["name"] = self.name
        d["building_type"] = self.building_type
        d["mpoly"] = self.building_to_dict()
        return shapely.dumps(d)

现在在主文件中，我有以下路由：

app.py

@app.route('/geojson')
def get_json():
    features = session.query(Building.mpoly.ST_AsGeoJSON()).all()
    return jsonify(features)

这是我的两个问题：

1) 返回类似于 JSON 的响应，如下所示： "{\"type\":\"MultiPolygon\",\"coordinates\":[[[[16.8933137,52.471446],...,]]]}" 不是正确的 GeoJSON。jsonify 之前的特征变量看起来是这样的： [('{"type":"MultiPolygon","coordinates":[[[[16.914159616,52.473822807],...,]]]}',)]

2) 我的 GeoAlchemy 查询应该是什么样子，不仅返回几何字段，还返回其他字段？

任何形式的提示或帮助高度赞赏，在此先感谢！

4

1 回答 1

1

您可以使用marshmallow-sqlalchemy创建类似 json 的响应。

创造 schemas.py

    #!schemas.py
    from marshmallow import fields
    from marshmallow_sqlalchemy import ModelSchema
    from app.models import Building
    from geoalchemy.shape import to_shape


    class BuildingSchema(ModelSchema):
        id = fields.Integer()
        district = fileds.Unicode()
        address = fileds.Unicode()
        name = fields.Unicode()
        building_type = fields.Unicode()
        mpoly = fileds.Method("geom_to_json")
    
        @staticmethod
        def geom_to_json(obj):
            mpoly = to_shape(obj.mpoly)
            return {
                    lat: mpoly.y,
                    lon: mpoly.x,
                    #and so on ... 
                    } 
        
        class Meta:
            model = Building
            exclude = ("mpoly")
            

    bulding_schema = BuildingSchema(many=True)

在此之后，您可以在您的视图（路线）中使用它

    from app.schemas import building_schema 


    @app.route('/geojson')
    def json():
        buildings = Buildings.query.all()
        response = building_schema.dumps(buildings)
        
        return response
于 2020-08-07T07:22:46.027 回答