[SOLVED] Exporting subgraph (sideeffect) to json file and importing back in graph

Exporting subgraph (sideeffect) to json file and importing back in graph

I want to export subgraph to json file and import in other graph. I tried as follows:

gremlin> subGraph = g.V().has("name","john").outE("has").subgraph("subgraph").cap("subgraph").next()
==>tinkergraph[vertices:6 edges:5]

now i have sub graph object then i used graphson to write this subgraph object directly to json file as follows:

subGraph.io(GraphSONIo.build()).writeGraph("/tmp/subgraph.json")

But i am getting error like this:

(was java.lang.IllegalStateException) (through reference chain: com.thinkaurelius.titan.graphdb.relations.RelationIdentifier["inVertexId"])

what is problem ??

Solution

I think the problem is that you have a TinkerGraph as your subgraph but that subgraph contains a Titan identifiers which GraphSON doesn't know how to natively process. You need to provide the Titan serializers to GraphSON so that it knows how to deal with the RelationIdentifier. You don't say what version of Titan you are using, but I think this approach works regardless of the version:

mapper = GraphSONMapper.build().
                        addCustomModule(TitanGraphSONModule.getInstance()).
                        create()
writer = GraphSONWriter.build().mapper(mapper).create()
os = new FileOutputStream("/tmp/subgraph.json")
writer.writeGraph(os, subgraph)

The more modern approach for JanusGraph would be:

sg.io('/tmp/sample.json').
     by(IO.registry, org.janusgraph.graphdb.tinkerpop.io.graphson.JanusGraphSONModuleV2d0.getInstance()).
   write().iterate()