havocp / play-geojson

GeoJSON support for Play's JSON library

Play GeoJSON Library

This is an unofficial library that provides GeoJSON support to Play that you may find useful.

Since it is unofficial, don't expect any support, bug fixes or updates in any sort of timely manner. Also don't expect any sort of backwards compatibility between releases. But do expect to find comprehensive support for the GeoJSON spec using Play's JSON API. This project may also be a useful tool to learning how to do some more complex things such as polymorphic structures in Play's JSON API.

Features

• Supports all GeoJSON types, including Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon, GeometryCollection, Feature, FeatureCollection.
• Supports any CRS, with WGS84 (latitude, longitude) provided out of the box.
• Type safe and polymorphic serialisation and deserialisation.
• Correctly adds the crs parameter according to the spec.
• Supports bounding boxes.
• Supports optional ids and properties of features.

Installation instructions

Add the following dependency to build.sbt:

"com.typesafe.play.extras" %% "play-geojson" % "1.1.0"

Usage instructions

Import the types you need:

import play.extras.geojson._

Serialise a GeoJSON object to a JSON:

val sydney = Feature(Point(LatLng(-33.86, 151.2111)), 
    properties = Json.obj("name" -> "Sydney"))
val json = Json.toJson(sydney)

Deserialise some JSON into a GeoJSON object:

val json = Json.obj(
  "type" -> "Feature",
  "geometry" -> Json.obj(
    "type" -> "Point",
    "coordinates" -> Seq(151.2111, -33.86)
  ),
  "properties" -> Json.obj(
    "name" -> "Sydney"
  )
)
val sydney = Json.fromJson[Feature[LatLng]](json)

Implement a custom CRS:

case class SphericalMercator(x: Int, y: Int)

object SphericalMercator {
  implicit val format: Format[SphericalMercator] = SphericalMercatorCrs.format
  implicit val crs: CrsFormat[SphericalMercator] = SphericalMercatorCrs
}

object SphericalMercatorCrs extends CrsFormat[SphericalMercator] {
  val crs = NamedCrs("urn:ogc:def:crs:EPSG::3857")
  val format = Format[SphericalMercator](
    __.read[Seq[Int]].map {
      case Seq(x, y) => SphericalMercator(x, y)
    }, Writes(m => Json.arr(m.x, m.y))
  )
}