Sample to create read a geotools FeatureCollection with properties in java / kotlin

createFeatureCollection.kt

package demo

import org.geotools.feature.DefaultFeatureCollection
import org.geotools.feature.simple.SimpleFeatureBuilder
import org.geotools.feature.simple.SimpleFeatureTypeBuilder
import org.geotools.referencing.crs.DefaultGeographicCRS.WGS84
import org.locationtech.jts.geom.Coordinate
import org.locationtech.jts.geom.GeometryFactory
import org.locationtech.jts.geom.Point


fun main() {
  val typeBuilder = SimpleFeatureTypeBuilder()
  typeBuilder.name = "points"
  typeBuilder.crs = WGS84
  typeBuilder.add("Geometry", Point::class.java)
  typeBuilder.add("blabla", Int::class.java)
  typeBuilder.add("age", Int::class.java)
  typeBuilder.add("stuff", String::class.java)

  val type = typeBuilder.buildFeatureType()
  val featureBuilder = SimpleFeatureBuilder(type)
  featureBuilder.add(GeometryFactory().createPoint(Coordinate(5.0, 2.0)))
  // respect properties order
  featureBuilder.add(32)
  featureBuilder.add(999)
  featureBuilder.add("hello world")

  val featureCollection = DefaultFeatureCollection("id-fc1", type)
  featureCollection.add(featureBuilder.buildFeature("id-f1"))

  val feature = featureCollection.features().next()
  println(feature.getProperty("age").value)
  println(feature.getProperty("stuff").value)
  println(feature.getProperty("blabla").value)
  println((feature.defaultGeometry as Point).coordinate)
}

readFeatureCollection.kt

package demo

import com.fasterxml.jackson.databind.DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES
import com.fasterxml.jackson.databind.ObjectMapper
import org.geotools.feature.FeatureIterator
import org.geotools.geojson.feature.FeatureJSON
import org.locationtech.jts.geom.MultiPolygon
import org.opengis.feature.Feature
import org.opengis.feature.simple.SimpleFeature

fun read() {
  // https://datahub.io/core/geo-countries
  val featureJson = this::class.java.getResource("/countries.geojson")?.readText()!!

  val fc = FeatureJSON().readFeatureCollection(featureJson)
  val features: FeatureIterator<Feature> = fc.features()
  while(features.hasNext()) {
    val feature = features.next()
    val simpleFeature = (feature as SimpleFeature)
    println(simpleFeature.getProperty("ISO_A3").value)
    val multiPolygon = simpleFeature.defaultGeometry as MultiPolygon
    (0 until multiPolygon.numGeometries).forEach {
      println(multiPolygon.getGeometryN(it).coordinates.size)
    }
  }
  println("over")
}