kgeojson

A simple GeoJson library written in Kotlin.

kgeojson rely on kotlinx serialization to encode and decode GeoJson data.

Usage

There's a simple example of encoding a feature collection with a single Point.

val featureCollection = 
  FeatureCollection(mutableListOf(
    Feature(
      Point(listOf(-74.001202, 40.713336)))))
val fcEncoded = Json.encodeToString(featureCollection as GeoJson)
println(fcEncoded)

Will result in:

{
  "type": "FeatureCollection",
  "features":[
  {
    "type":"Feature",
    "geometry":{
      "type":"Point",
      "coordinates": [ -74.001202, 40.713336 ]
     },
     "properties":{}
  }
 ]
}

Notice the as GeoJson in the encodeToString call. When encoding, we need to tell kotlinx to use the parent sealed class, so he puts the type discriminator field in the serialized object.

That's part of a kotlinx serialization limitation discussed here (maybe fixed in a future release). If you don't pass the target object as the parent sealed class, the object will be serialized without the type discriminator field. This will result in a non RFC7946 compliant GeoJson.

So it's recommended to always pass the target as the parent, in kgeojson it means to add as GeoJson on every encodeToString call, that's it.

Supported types

• FeatureCollection
• Feature
• Point
• MultiPoint
• LineString
• MultiLineString
• Polygon
• GeometryCollection