Convert GeoJSON object to GML geometry - jackson

Question

I have the following issue with transforming GeoJSON object into GML geometry object.
First, on backend in request I retrieve GeoJSON object.
Then I use jackson library to transform it into java object. This java object is FeatureCollection from geojson-jackson library.
So I have java object representing GeoJSON on backend and now I need to transform it into GML object and extract geometry from it.
From this:
{
"featureCollection : {
"type": "FeatureCollection",
"features": [{
"type": "Feature",
"geometry": {
"type": "Polygon",
"coordinates": [ [[100.0,0.0],[101.0,0.0],[101.0,1.0],[100.0,1.0],[100.0,0.0]] ]
},
}]
}
}
I need to get this:
<gml:Rectangle srsName="urn:x-ogc:def:crs:EPSG:6.6:25833">
<gml:exterior>
<gml:LinearRing>
<gml:coordinates>100.0,0.0 101.0,0.0 101.0,1.0 100.0,1.0 100.0,0.0</gml:coordinates>
</gml:LinearRing>
</gml:exterior>
</gml:Rectangle>
The question, is there any existing library which allows transform from GeoJSON into GML object?

Answer 1

Geotools can probably do what you need. I would not have posted, since I have not done this, but a speculative recipe is better than "definitely not".
GeoTools can read GeoJSON and give you a JTS geometry or a Feature, which can then be used to generate GML using a org.geotools.xml.Encoder.
Use org.geotools.geojson.feature.FeatureJSON or org.geotools.geojson.geom.GeometryJSON to take a JSON string and give a Geometry instance, like this:
GeometryJSON gJson = new GeometryJSON();
jtsGeometry = gJson.readGeometryCollection(jsonInputStream)
Then configure an encoder to write GML.
org.geotools.xml.Encoder encoder = new org.geotools.xml.Encoder(...);
...
encoder.encode(jtsGeometry, qName, outputStream);
I hope this is enough to started. Perhaps if you get it working (or find it impossible) come back and edit this post.

Answer 2

As far as i know, there is no such thing for java. ogr2ogr (a commandline utility) can do that:
converts simple features data between file formats
http://www.gdal.org/ogr2ogr.html
ogr2ogr -f "GML" destination.gml source.geojson
You can run that from java, see this question: How to run GDAL (ogr2ogr) in Java to convert Shapefiles to GeoJSON

Answer 3

No, there is definetly not. You have to find another way to do that.
I suggest you to do that either manually or read it as file and save to variables.