We are interested in serving out geospatial features in a standardised data
exchange format using the Google Endpoints API. We have used the API to be
able to serve out Point features (code below), and overlay the points on to
a map using the Google Maps API. Now we would like to serve out polygons
and are having difficulty constructing the required response using the
Endpoints API.
Example Of GeoJSON Point:
{ "type": "FeatureCollection",
"features": [
{ "type": "Feature",
"geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
"properties": {"name": "my point"}
}
]
}
To do this we defined the following Endpoints Message Classes:
class Geometry(messages.Message):
type = messages.StringField(1)
coordinates = messages.FloatField(2, repeated=True)
class Properties(messages.Message):
name = messages.StringField(1)
class Feature(messages.Message):
type = messages.StringField(1)
geometry = messages.MessageField(Geometry, 2)
properties = messages.MessageField(Properties, 3)
class FeatureCollection(messages.Message):
type = messages.StringField(1)
features = messages.MessageField(Feature, 2, repeated = True)
A GeoJSON Point feature collection could then be constructed using the
following Endpoint code:
@endpoints.method(message_types.VoidMessage, FeatureCollection,
path='user/mus', http_method='GET',
name='user.mus.getManagementUnits')
def user_endpoint_mu_list(self, unused_request):
feats = []
coords = [102.0, 0.5]
geom = Geometry(type='Point', coordinates=coords)
prop = Properties(name='my point')
feat = Feature(type='Feature', geometry=geom, properties=prop)
feats.append(feat)
ret = FeatureCollection(type='FeatureCollection', features=feats)
return ret
The point could then be overlayed on to google maps by invoking the
Endpoint using the following javascript code:
gapi.client.irrisat.user.mus.getManagementUnits().execute(
function (result) {
map.data.addGeoJson(result);
});
Now we would like to serve out polygon feature types using the Endpoints
API (example response below). This is similar to the point response however
the type is now "Polygon", and the coordinates for the polygon are
described by an array of coordinate point arrays:
{ "type": "FeatureCollection",
"features": [
{ "type": "Feature",
"geometry": {"type": "Polygon", "coordinates": [[102.0, 0.5], [103.0
, 0.8], [105.0, 0.2]]},
"properties": {"name": "my polygon"}
}
]
}
We are unsure how to construct the "coordinates" field for a polygon
response. The Endpoints API specified the following types can be used in an
Endpoints response:
class BooleanField()
class BytesField()
class EnumField()
class FloatField()
class IntegerField()
class MessageField()
class StringField()
class DateTimeField()
However the type required for the coordinates field for a polygon is an
Array of Arrays so to speak. Is there a way to properly construct a GeoJSON
polygon response according to the GeoJSON specifications
<http://geojson.org/geojson-spec.html>?
Jamie
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