Simple library for reading and writing GeoJSON files in Java/Kotlin, using JTS Geometry classes.
This library uses a bit of relaxed version of GeoJSON standard. It does not bother with validating some of GeoJSON annoyingly strict contracts, like requirement of all Features in same file having same set of properties or same type of Geometry. Thus you may create files that won't be read properly by some tools that obey standards strictly. But this makes using GeoJSON much easier.
Library provides simple classes for Feature and FeatureCollection, that can directly be read and written using Gson library.
import java.io.OutputStream
val geom = Geometry(...) // JTS Geometry
val feature = Feature(geom, mutableMapOf("prop1" to "val1", "prop2" to "val2")) //
val fc = FeatureCollection(feature)
// Save FC to GeoJSON output stream
GeoJSONImportExport.writeFeatureCollection(OutputStream(...), fc)
// Read GeoJSON file
val fcFromFile = GeoJSONIMportExport.readFeatureCollection(InputStream(...))
// Access feature geometries and properties
fcFromFile.features[0].geometry
fcFromFile.features[1].properties["prop1"]