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私の人生では、neo4j 1.9.4 コミュニティ エディションで既に作成したグラフを読み取れない理由が理解できません。Eclipse では、次のコードを実行します。

public class neo4jtest {

    private GraphDatabaseService graphDb;
    private static final String neo4j_db = "c:/tmp/db/neo4j-new-db";
    private UniqueFactory<Node> nodefactory;
    private static enum RelTypes implements RelationshipType
    {
        FRIEND, FOLLOWER
    }

    public neo4jtest() {

        graphDb = new GraphDatabaseFactory().newEmbeddedDatabaseBuilder(neo4j_db).
                setConfig( GraphDatabaseSettings.node_keys_indexable, "ScreenName,ID" ).
                setConfig( GraphDatabaseSettings.relationship_keys_indexable, (RelTypes.FRIEND).name()+","+(RelTypes.FOLLOWER).name()).
                setConfig( GraphDatabaseSettings.node_auto_indexing, "true" ).
                setConfig( GraphDatabaseSettings.relationship_auto_indexing, "true" ).
                newGraphDatabase();
        //graphDb = new GraphDatabaseFactory().newEmbeddedDatabase(neo4j_db);
        registerShutdownHook( graphDb );
        nodefactory = new UniqueFactory.UniqueNodeFactory( graphDb, "users" )
        {
            @Override
            protected void initialize( Node created, Map<String, Object> properties )
            {
                created.setProperty( "ScreenName", properties.get( "ScreenName" ) );
            }
        };
    }

    public void exit() {
        graphDb.shutdown();
    }

    public static void main(String[] args) {

        neo4jtest n4 = new neo4jtest();
        String u1 = "Moe";
        //Node unode = n4.createNeo4jGraph(u1);
        n4.exploreNeo4jGraph(u1);
        n4.exit();
    }

    public Node createNeo4jGraph(String uname) {

        Node firstNode;
        Relationship relationship;  
        // build a graph
        try {
            Transaction tx = graphDb.beginTx();
            firstNode = nodefactory.getOrCreate("ScreenName", uname);
            firstNode.setProperty( "ScreenName", uname );
            firstNode.setProperty("ID", 1);
            Node followerNode = nodefactory.getOrCreate("ScreenName", "Larry");
            followerNode.setProperty("ID", 2);  
            relationship = firstNode.createRelationshipTo( followerNode, RelTypes.FOLLOWER ); // may not be unique
            relationship = followerNode.createRelationshipTo(firstNode, RelTypes.FRIEND);
            followerNode = nodefactory.getOrCreate("ScreenName", "Curly");
            followerNode.setProperty("ID", 3);
            relationship = firstNode.createRelationshipTo( followerNode, RelTypes.FOLLOWER ); // may not be unique
            relationship = followerNode.createRelationshipTo(firstNode, RelTypes.FRIEND);
            tx.success();
            return firstNode;
        } catch(Exception ex) {}
        return null;
    }

    private void exploreNeo4jGraph(String scname) {
        // use the auto indexer to lookup node with string name
        // Get the Node auto index
        ReadableIndex<Node> autoNodeIndex = graphDb.index()
                .getNodeAutoIndexer()
                .getAutoIndex();

        Node mainUser = autoNodeIndex.get( "ScreenName", scname ).getSingle();

        if (mainUser==null) {
            // why not use nodefactory to get it?
            System.out.println("Auto indexer did not work");
            mainUser = nodefactory.getOrCreate("ScreenName", scname);
        }
        exploreNeo4jGraph(mainUser);                
    }

    private void exploreNeo4jGraph(Node unode) {
        // explore the nodes and edges in the graph
        if (unode==null) {
            System.err.println("Cannot explore from null node!");
            return;
        }
        long currRels = IteratorUtil.count(GlobalGraphOperations.at(graphDb).getAllRelationships());
        long currNodes = IteratorUtil.count(GlobalGraphOperations.at(graphDb).getAllNodes());

        System.out.println("Number of nodes in graph is " + currNodes);
        System.out.println("Number of edges in graph is " + currRels);

        int numberOfFollowers = 0;
        String output = unode.getProperty( "ScreenName" ) + "'s friends:\n";
        Traverser friendsTraverser = getFriends( unode );
        for ( Path friendPath : friendsTraverser )
        {
            output += "At depth " + friendPath.length() + " <= "
                    + friendPath.endNode().getProperty( "ScreenName" ) + "\n";
            numberOfFollowers++;
        }
        output += "Number of friends found: " + numberOfFollowers + "\n";
        System.out.println(output);
}

    private Traverser getFriends(final Node person )
    {
        TraversalDescription td = Traversal.description()
                .breadthFirst()
                .relationships( RelTypes.FRIEND, Direction.INCOMING )
                .evaluator( Evaluators.excludeStartPosition() );
        return td.traverse( person );
    }

    private static void registerShutdownHook( final GraphDatabaseService graphDb )
    {
        // Registers a shutdown hook for the Neo4j instance so that it
        // shuts down nicely when the VM exits (even if you "Ctrl-C" the
        // running application).
        Runtime.getRuntime().addShutdownHook( new Thread()
        {
            @Override
            public void run()
            {
                graphDb.shutdown();
            }
        } );
    }
}

基本的に、私は行のコメントを外します

Node unode = n4.createNeo4jGraph(u1);

グラフを作成します。

次に、その行をコメントにして再度実行し、作成されたグラフを調べます。再度実行すると、作成されたグラフが報告されません。私は何を間違っていますか？

ありがとう

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1 に答える 1

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取引を終了する必要があると思います。javadoc から: (in 1.9)以前に呼び出されたかどうかfinish()に応じて、このトランザクションをロールバック用にコミットまたはマークします。success()failure()

于 2013-11-13T08:02:43.787 に答える