A Neo4j REST Server Plugin to request contact paths

ContactPaths.scala

import org.neo4j.graphdb.GraphDatabaseService
import org.neo4j.graphdb.Node
import org.neo4j.server.plugins._
import org.neo4j.graphalgo.GraphAlgoFactory
import org.neo4j.kernel.OrderedByTypeExpander
import org.neo4j.graphdb.RelationshipType
import org.neo4j.graphdb.Path
import org.neo4j.helpers.collection.NestingIterable
import org.neo4j.helpers.collection.NestingIterator
import collection.JavaConversions.{asJavaIterable, asScalaIterable}

@Description( "An extension to the Neo4j Server for getting all nodes or relationships" )
class ContactPaths extends ServerPlugin {

  @Name("get_shortest_path")
  @Description( "Get shortest contact path from one user to another" )
  @PluginTarget( classOf[GraphDatabaseService] )
  def getShortestPath( @Source graphDb: GraphDatabaseService, @Parameter(name="from") 
    from: Node, @Parameter(name="to") to: Node): java.lang.Iterable[Node] = {
    val algo = GraphAlgoFactory.shortestPath(new OrderedByTypeExpander().add(Relationship.contact), 5)
    algo.findSinglePath(from, to) match {
      case null => new java.util.ArrayList[Node]()
      case x => x.nodes()
    }
  }

  implicit object PathCollectionOrdering extends Ordering[Path] {
    def compare(first: Path, second: Path) =
      first.length - second.length
  }

  case class PathCollection(paths: Iterable[Path]) extends NestingIterable[Node, Path](paths) {
    def createNestedIterator(path: Path): java.util.Iterator[Node] = path.nodes.iterator
  }
  
  implicit def iterable2PathCollection(paths: java.lang.Iterable[Path]) = PathCollection(paths)
  implicit def iterable2PathCollection(paths: Iterable[Path]) = PathCollection(paths)

  @Name("get_all_paths")
  @Description( "Get all contact paths from one user to another" )
  @PluginTarget( classOf[GraphDatabaseService] )
  def getAllPaths( @Source graphDb: GraphDatabaseService, @Parameter(name="from")
    from: Node, @Parameter(name="to") to: Node): NestingIterable[Node, Path] = {
    val algo = GraphAlgoFactory.allPaths(new OrderedByTypeExpander().add(Relationship.contact), 5)
    algo.findAllPaths(from, to) match {
      case null => List[Path]()
      case x => x
    }
  }
}

Relationship.java

import org.neo4j.graphdb.RelationshipType;

enum Relationship implements RelationshipType {
  contact
}