gremlin-scala

A thin wrapper for Gremlin so that it feels natural to use the Gremlin graph DSL in Scala. Gremlin is a domain specific language for traversing a number of graph databases including Neo4j, OrientDB, DEX, InfiniteGraph, Titan, Rexster graph server and Sesame 2.0 compliant RDF stores.

For more information about Gremlin see the Gremlin wiki. Gremlin-Steps and Methods will give you a quick deep dive.

Sample usage

  // this is an executable ScalaTest specification - see SampleUsageTest.scala for full setup
  describe("Gremlin-Scala") {
    val graph = TinkerGraphFactory.createTinkerGraph
    def vertices = graph.V
  
    it("finds all vertices") {
      vertices.count should be(6)
      vertices.map.toList.toString should be(
        "[{name=lop, lang=java}, {name=vadas, age=27}, {name=marko, age=29}, " +
          "{name=peter, age=35}, {name=ripple, lang=java}, {name=josh, age=32}]"
      )
    }

    it("can get a specific vertex by id and get it's properties") {
      val marko = graph.v(1)
      marko("name") should be("marko")
      marko("age") should be(29)
    }

    it("finds everybody who is over 30 years old") {
      vertices.filter { v: Vertex ⇒
        v.as[Int]("age") match {
          case Some(age) if age > 30 ⇒ true
          case _                     ⇒ false
        }
      }.map.toList.toString should be(
        "[{name=peter, age=35}, {name=josh, age=32}]")
    }

    it("finds who marko knows") {
      val marko = graph.v(1)
      marko.out("knows")(_("name"))
        .toList.toString should be("[vadas, josh]")
    }

    it("finds who marko knows if a given edge property `weight` is > 0.8") {
      val marko = graph.v(1)
      marko.outE("knows").filter { e: Edge ⇒
        e.as[Float]("weight") match {
          case Some(weight) if weight > 0.8 ⇒ true
          case _                            ⇒ false
        }
      }.inV.map.toList.toString should be("[{name=josh, age=32}]")
    }
  }

Gremlin-Console

You can play with Gremlin in an interactive console:

         \,,,/
         (o o)
-----oOOo-(_)-oOOo-----
# create a sample in-memory graph
gremlin> val g = TinkerGraphFactory.createTinkerGraph
==> tinkergraph[vertices:6 edges:6]

# list all vertices
gremlin> g.V
==> v[3]
==> v[2]
==> v[1]
==> v[6]
==> v[5]
==> v[4]

# show properties map of the vertices
gremlin> g.V.map
==> {name=lop, lang=java}
==> {name=vadas, age=27}
==> {name=marko, age=29}
==> {name=peter, age=35}
==> {name=ripple, lang=java}
==> {name=josh, age=32}

# show names of all vertices
gremlin> g.V.property("name")
==>lop
==>vadas
==>marko
==>peter
==>ripple
==>josh

# get marko's vertex
gremlin> val marko = g.v(1)
==> v[1]

gremlin> marko("age")
==> 29

# find marko's friends' names
gremlin> marko.out("knows")(_("name"))
==> vadas
==> josh

# create a new graph with two vertices and an edge between them
val g = new TinkerGraph()
val v1 = graph.addV()
val v2 = graph.addV()
graph.addE(v1, v2, "label")

For many more examples (in Gremlin-Groovy syntax) see the [Getting started page of Gremlin (in groovy syntax)]https://github.com/tinkerpop/gremlin/wiki/Getting-Started].
This is a normal Scala REPL, so you run arbitrary Scala code here. 

Building Gremlin-Scala

git clone https://github.com/mpollmeier/gremlin-scala.git
mvn test      #run all tests - should find all dependencies and run the tests fine
mvn install   #install into your local maven repository so that you can use it (groupId=com.tinkerpop.gremlin, artifactId=gremlin-scala

Kudos go to Zach Cox for starting this project and the whole Tinkerpop team for creating a whole awesome stack around graph databases.