How can I find a path between given two nodes?

Question

How can I find a path between given two nodes in neo4j Java API, the product of all weights of the path is maximum in all paths between two nodes, what can I do? In my graph database, there are two elements: one is node, another is relationship, and all have a name property, but the relationship have an extra property: weight (double type, and values in (0,1]). My code as follows: How do I modify？

public static ArrayList<Path> getAllOptPaths(Long startNodeId, Long endNodeId, GraphDatabaseService db){
    ArrayList<Path> optPathsBetweenTwoNodes = new ArrayList<Path>();
    try (Transaction tx = db.beginTx()){
        Node node1 = db.getNodeById(startNodeId);
        Node node2 = db.getNodeById(endNodeId);

        PathExpander<Object> pathExpander = PathExpanders.allTypesAndDirections();
        CostEvaluator<Double> costEvaluator = CommonEvaluators.doubleCostEvaluator("Cost");

        // find all paths between given two nodes
        PathFinder<WeightedPath> dijkstraPathsFinder = GraphAlgoFactory.dijkstra(pathExpander, costEvaluator);
        WeightedPath path = dijkstraPathsFinder.findSinglePath(node1, node2);

        optPathsBetweenTwoNodes.add(path);

        tx.success();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return optPathsBetweenTwoNodes;       
}

Answer 1

Exploring paths is also possible in a cypher query. This can deliver you the result of a weighted path calculation (and thus the path with the minimum weight on it) as a result.

This webpage contains an example of a weighted path query. Also, the Neo4j reduce function will help you to specify how to calculate (and weigh) your paths.

Answer 2

This problem has been resolved by myself, and the method is modify the source of neo4j core JAVA API.In the process of modifying source involved some specific documents as follows:Dijkstra.java, BestFirstSelectoryFactory.java, GraphAlgoFactory.java, Path.java, WeightedPathImpl.java, WeightedPathIterator.java. If anyone is interested in the detail of modify, you can send mail to me.

Answer 3

Changing the codebase is not a good idea as I think. You can set the weight of the edges with key "Cost" when you set the property of the relationship (weight of the edge for example) using function setProperty().