Question

… always getting exceptions when creating a edge/relation between a vertex and the Neo4j – ReferenceNode.

How to handle something like this?

GraphDatabaseService neoGraphDbService = new EmbeddedGraphDatabase( "d:/testDb" );
System.out.println(neoGraphDbService.getReferenceNode()); // Node[0]

Graph tiGraphDb = new Neo4jGraph(neoGraphDbService);

Vertex referenceNode = tiGraphDb.getVertex(0);

//throws Exception:
//org.neo4j.graphdb.NotFoundException: Node[0]
System.out.println(neoGraphDbService.getReferenceNode());

//referenceNode is null
System.out.println(referenceNode);

Vertex a = tiGraphDb.addVertex(null);
Vertex b = tiGraphDb.addVertex(null);

a.setProperty("name","marko");
b.setProperty("name","peter");

Edge referenceNode_knows_a = tiGraphDb.addEdge(null, referenceNode, a, "knows");
Edge a_knows_b = tiGraphDb.addEdge(null, a, b, "knows");

tiGraphDb.shutdown();

This is my first experience with tinkerpop and i don´t understand what is really happening with the referenceNode, it seems to get lost as soon as i make a tinkerpop connection…

btw. there are no tags yet for tinkerpop, blueprints etc…

Answer 1

if you don’t specify that the graph is not fresh, blueprints deletes the reference node. Try

Graph tiGraphDb = new Neo4jGraph(neoGraphDbService, false);

To keep Blueprints from meddling with the graph.

/peter