That worked... thanks for the insight into how Expander is used. Much appreciated...
-- Bernie -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Andres Taylor Sent: Friday, October 08, 2010 4:04 PM To: Neo4j user discussions Subject: Re: [Neo4j] PathFinder.findSinglePath returns null Hi again, Tobias just pointed out to me what is the problem with the code. OrderedByTypeExpander is an immutable class. So where it says: StandardExpander expander = new OrderedByTypeExpander(); expander.add(RelationshipTypes.KNOWS, Direction.OUTGOING); expander.add(RelationshipTypes.LIKES, Direction.OUTGOING); it should really say: StandardExpander expander = new OrderedByTypeExpander(); expander = expander.add(RelationshipTypes.KNOWS, Direction.OUTGOING); expander = expander.add(RelationshipTypes.LIKES, Direction.OUTGOING); The add method returns a new expander with the RelationshipType added. Does this code work for you? Cheers, Andrés On Fri, Oct 8, 2010 at 9:46 PM, Andres Taylor < [email protected]> wrote: > Hi there, > > I've looked over your code, and it doesn't seem like you are doing > anything wrong, AFAICS. > > It would be easier to help you if I could run the code, and I would > need to have a copy of your database for that. Could you send a script > that loads a database with data? > > Cheers, > > Andrés > > On Fri, Oct 8, 2010 at 5:30 PM, French, Bernie T. <[email protected]> wrote: > >> Hi Folks, >> >> I just joined the list and have begun my initial explorations of neo4j. >> I've been able to build a simple directed graph database, create a >> TraversalDescription, traverse the graph and write a Pruner. >> >> I then started to explore the graph algorithms, starting with the >> "shortest path" algorithm from the GraphAlgoFactory class. Although >> I can traverse my graph using a Traverser, I cannot seem to be able >> to get a path from using the GraphAlgoFactory. >> >> The path that is always returned by the following statement is always >> null, even though I know the path exists using the Traverser. >> >> path = pathFinder.findSinglePath(startNode, endNode); >> >> Here is the snapshot of my class, first using the Traverser, and then >> trying to use the Graph Algorithms. Any insight into what I'm >> overlooking would be greatly appreciated. >> >> public class FindShortestPath { >> >> public static void main(String[] args) { >> >> String databaseLocation = >> "/home/neo4j/simpleDirectedGraphDb"; >> GraphDatabaseService graphDb = new >> EmbeddedGraphDatabase(databaseLocation); >> IndexService indexService = new >> LuceneIndexService(graphDb); >> Transaction tx = graphDb.beginTx(); >> PropertyContainer propertyContainer; >> StringBuffer pathBuffer; >> try { >> >> String startName = "Jack"; >> String endName = "Jill"; >> Node startNode = >> indexService.getSingleNode("NAME", startName); >> Node endNode = >> indexService.getSingleNode("NAME", endName); >> System.out.println("StartNode: " + >> startNode.getProperty("NAME")); >> System.out.println("EndNode: " + >> endNode.getProperty("NAME")); >> >> // Traverse the Graph - Traversing is >> successfull here.... >> >> TraversalDescription td = new >> TraversalDescriptionImpl(); >> td = td.depthFirst(); >> td = td.relationships(RelationshipTypes.LIKES, >> Direction.OUTGOING); >> td = td.relationships(RelationshipTypes.KNOWS, >> Direction.OUTGOING); >> Traverser traverser = td.traverse(startNode); >> Iterator<Path> traversalIterator = >> traverser.iterator(); >> int pathCount = 0; >> Path path = null; >> while (traversalIterator.hasNext()) { >> pathCount++; >> path = (Path) >> traversalIterator.next(); >> >> Iterable<Node> nodeIterable = >> path.nodes(); >> Iterator<Node> nodeIterator = >> nodeIterable.iterator(); >> pathBuffer = new StringBuffer(); >> while (nodeIterator.hasNext()) { >> Node node = (Node) >> nodeIterator.next(); >> >> pathBuffer.append(node.getProperty("NAME") + "->"); >> } >> System.out.println("TRAVERSE: " + >> pathBuffer.toString()); >> >> } >> >> // Start Graph Algorithm >> >> StandardExpander expander = new >> OrderedByTypeExpander(); >> expander.add(RelationshipTypes.KNOWS, >> Direction.OUTGOING); >> expander.add(RelationshipTypes.LIKES, >> Direction.OUTGOING); >> PathFinder<Path> pathFinder = >> GraphAlgoFactory.shortestPath(expander, 20); >> >> path = pathFinder.findSinglePath(startNode, >> endNode); >> >> /* PATH IS ALWAYS NULL HERE */ >> >> if (path != null) { >> Iterator<PropertyContainer> >> pathIterator = path.iterator(); >> pathBuffer = new StringBuffer(); >> while (pathIterator.hasNext()) { >> propertyContainer = >> (PropertyContainer) pathIterator.next(); >> String name = (String) >> propertyContainer.getProperty("NAME"); >> pathBuffer.append(name + "->"); >> } >> System.out.println("Single Path: " + >> pathBuffer.toString()); >> } else { >> System.out.println("Could not find a >> path, path is null"); >> } >> tx.success(); >> } catch (Exception e) { >> e.printStackTrace(); >> graphDb.shutdown(); >> } >> graphDb.shutdown(); >> >> } >> >> } >> >> Thanks! >> >> -- Bernie >> >> >> >> Confidentiality Notice: This electronic message transmission, >> including any attachment(s), may contain confidential, proprietary, >> or privileged information from Chemical Abstracts Service ("CAS"), a >> division of the American Chemical Society ("ACS"). 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