Add weight to a relationship using neo4j embedded java api

Question

I would like to add a weight to a relationship using Embedded Neo4j Java API.

For example : A knows B very well so their relationship should be weighted 5. On the other hand, A knows C very little so their relationship should be weighted 1.

How can I do that?

PS : I have already tried the example here : http://neo4j.com/docs/stable/tutorials-java-embedded-graph-algo.html but it doesn't recognize th functions createNode( "name", "A", "x", 0d, "y", 0d ) and createRelationship( nodeA, nodeC, "length", 2d ).

This is the code :

package com.neo4j.test.test1;

import org.neo4j.graphalgo.CommonEvaluators;
import org.neo4j.graphalgo.EstimateEvaluator;
import org.neo4j.graphalgo.GraphAlgoFactory;
import org.neo4j.graphalgo.PathFinder;
import org.neo4j.graphalgo.WeightedPath;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.PathExpanders;
import org.neo4j.graphdb.Relationship;
import org.neo4j.graphdb.Transaction;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;

import com.neo4j.test.labels.NodeLabels;
import com.neo4j.test.labels.TypeRelation;

public class Test1 {

    public static void main(String[] args) {

        GraphDatabaseFactory dbFactory = new GraphDatabaseFactory();
        GraphDatabaseService db = dbFactory.newEmbeddedDatabase("C:\\Zakaria\\NeoTests\\Test2");

        try (Transaction tx = db.beginTx()) {

            Node nodeA = createNode( "name", "A", "x", 0d, "y", 0d );
            Node nodeB = createNode( "name", "B", "x", 7d, "y", 0d );
            Node nodeC = createNode( "name", "C", "x", 2d, "y", 1d );
            Relationship relAB = createRelationship( nodeA, nodeC, "length", 2d );
            Relationship relBC = createRelationship( nodeC, nodeB, "length", 3d );
            Relationship relAC = createRelationship( nodeA, nodeB, "length", 10d );

            EstimateEvaluator<Double> estimateEvaluator = new EstimateEvaluator<Double>()
            {
                @Override
                public Double getCost( final Node node, final Node goal )
                {
                    double dx = (Double) node.getProperty( "x" ) - (Double) goal.getProperty( "x" );
                    double dy = (Double) node.getProperty( "y" ) - (Double) goal.getProperty( "y" );
                    double result = Math.sqrt( Math.pow( dx, 2 ) + Math.pow( dy, 2 ) );
                    return result;
                }
            };
            PathFinder<WeightedPath> astar = GraphAlgoFactory.aStar(
                    PathExpanders.allTypesAndDirections(),
                    CommonEvaluators.doubleCostEvaluator( "length" ), estimateEvaluator );
            WeightedPath path = astar.findSinglePath( nodeA, nodeB );

            tx.success();

        }

        System.out.println("Done!");

    }

}

It should give this result :

enter image description here

It says that these following functions are not defined :

Node nodeA = createNode( "name", "A", "x", 0d, "y", 0d );
Node nodeB = createNode( "name", "B", "x", 7d, "y", 0d );
Node nodeC = createNode( "name", "C", "x", 2d, "y", 1d );
Relationship relAB = createRelationship( nodeA, nodeC, "length", 2d );
Relationship relBC = createRelationship( nodeC, nodeB, "length", 3d );
Relationship relAC = createRelationship( nodeA, nodeB, "length", 10d );

Thanks!

Please post the code you have tried, as well as any error messages it produces. — amphetamachine, Feb 24 '15 at 16:24

score 1 · Accepted Answer · answered Mar 27 '15 at 23:08

As said Ryan, Java compiler doesn't detect the methods createNode() and createRelationship() that you use.

This is a way to create the Nodes, and works for me:

try (Transaction Tx = gdbs.beginTx(){
    Node nodo = gdbs.createNode();
    nodo.addLabel(p);   // if you have Labels
    nodo.setProperty("property1", someValue);
    Tx.success();
    Tx.close();
} catch (Exception e){//do something}

For relationships, only show you how to add properties:

relationship = firstNode.createRelationshipTo(secondNode, RelTypes.KNOWS );
relationship.setProperty( "message", "brave Neo4j " );

Depending of your Neo4j version, you should see how create Nodes and Relationships. Last, I have you create nodes and relationships, and without commit them, you create the PathFinder. I recommend you persist the nodes before querying the graph as good practice.

score 0 · Answer 2 · answered Feb 24 '15 at 16:56

0

These methods aren't defined as methods in class Test1, but rather on GraphDatabaseService. So, you need to do db.createNode() and db.createRelationship(). That should work for you.

answered Feb 24 '15 at 16:56

Ryan Boyd

2,978
1
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Can you define how it didn't work? What was the specific error? – Ryan Boyd Feb 24 '15 at 17:06
It is just as you said, `These methods aren't defined as methods in class Test1` – user1885868 Feb 24 '15 at 17:08
sorry, I meant: what is the error you get when you try db.createNode() and db.createRelationship. The methods are defined in anything implementing the GraphDatabaseService interface: http://neo4j.com/docs/stable/javadocs/org/neo4j/graphdb/GraphDatabaseService.html – Ryan Boyd Feb 24 '15 at 17:13

score 0 · Answer 3 · answered May 18 '17 at 21:29

0

The methods createNode() and createRelationship() are not defined in neo4j java API as you are using these.

answered May 18 '17 at 21:29

adas

1

Add weight to a relationship using neo4j embedded java api

3 Answers3