GraphSON and Instant

[Philip Graff]

Hi all,

I've run into an interesting issue with Java's Instant and GraphSON. I will illustrate with a simple example.

------------------------------------------------------------------------------------

Import Instant, open a graph, and add a vertex with a time value

gremlin> import java.time.Instant

gremlin> graph=TinkerGraph.open()

==>tinkergraph[vertices:0 edges:0]

gremlin> v = graph.addVertex()

==>v[0]

gremlin> v.property("time",Instant.now())

==>vp[time->2018-04-09T16:10:...]

This time is stored properly as an Instant

gremlin> v.value("time")

==>2018-04-09T16:10:43.688Z

gremlin> v.value("time").getClass()

==>class java.time.Instant

Save to GraphML, GraphSON, and Gryo

gremlin> graph.io(IoCore.graphml()).writeGraph("/tmp/graph.graphml")

==>null

gremlin> graph.io(IoCore.graphson()).writeGraph("/tmp/graph.graphson")

==>null

gremlin> graph.io(IoCore.gryo()).writeGraph("/tmp/graph.gryo")

==>null

Clear the graph

gremlin> graph.clear()

==>null

Import the graph from GraphML and check the time - it is now a String as expected

gremlin> graph.traversal().V().values("time").next().getClass()

==>class java.lang.String

Clear the graph

gremlin> graph.clear()

==>null

Import the graph from Gryo and check the time - it is an Instant as expected

gremlin> graph.io(IoCore.gryo()).readGraph("/tmp/graph.gryo")

==>null

gremlin> graph.traversal().V().values("time").next().getClass()

==>class java.time.Instant

Clear the graph

gremlin> graph.clear()

==>null

Import the graph from GraphSON and check the time - it is now a LinkedHashMap

gremlin> graph.io(IoCore.graphson()).readGraph("/tmp/graph.graphson")

==>null

gremlin> graph.traversal().V().values("time").next().getClass()

==>class java.util.LinkedHashMap

------------------------------------------------------------------------------------

Is this a known issue? Since GraphSON is typed shouldn't it store this as an Instant? Below is the pretty-printed GraphSON file which also seems to be storing the Instant in a weird way.

{

    "id": {

        "@type": "g:Int64",

        "@value": 0

    },

    "label": "vertex",

    "properties": {

        "time": [

            {

                "id": {

                    "@type": "g:Int64",

                    "@value": 1

                },

                "value": {

                    "nano": 688000000,

                    "epochSecond": {

                        "@type": "g:Int64",

                        "@value": 1523290243

                    }

                }

            }

        ]

    }

}

Thanks,
Phil

[Stephen Mallette]

Instant is part of the "extended" set of GraphSON types - you have to specify support for it explicitly:

http://tinkerpop.apache.org/docs/current/dev/io/#_extended

I think that explains what you are seeing.

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[Philip Graff]

OK, thanks, that's probably it. My next question is how do I use the mapper obtained by following the code in the documentation (excerpted below)?

mapper = GraphSONMapper.build().
                        typeInfo(TypeInfo.PARTIAL_TYPES).
                        addCustomModule(GraphSONXModuleV3d0.build().create(false)).
                        version(GraphSONVersion.V3_0).create().createMapper()

Thanks,

Phil

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[Stephen Mallette]

The reader/writer instances have mapper() methods on their Builder classes:

http://tinkerpop.apache.org/javadocs/current/full/org/apache/tinkerpop/gremlin/structure/io/graphson/GraphSONWriter.Builder.html#mapper-org.apache.tinkerpop.gremlin.structure.io.Mapper-

writer = GraphSONWriter.build().mapper(mapperWithExtension).create()

reader = GraphSONReader.build().mapper(mapperWithExtension).create()

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[Philip Graff]

Got it, thanks!