如何从Java获取Neo4j图形数据库的节点数，如何从磁盘存储和重用graphdb？

Question

I just started looking at neo4j to use it for my social-network related project. During this I came across the following code:

https://github.com/neo4j/neo4j/blob/1.9.M04/community/embedded-examples/src/main/java/org/neo4j/examples/EmbeddedNeo4jWithIndexing.java

While going through it (please refer to above link for code), I was struggling to know, how to get the total number of nodes added to a given graphDb . Is there any way to find it (total number of nodes) using graphDb or nodeIndex or referenceIndex or anything else? If yes, How?

I also need help to know, how to store the graphdb to any given path on disk? How to load this stored graphdb and perform operations on it like searching for a node/relationship etc?

(There are several files like *.db, *.id, *.keys etc.. created at given DB_PATH when above code is executed. What are all those files useful for? Does any of those files contain nodes created? if yes, how can we use them?)

How can we access this graphDb from web-interfaces like, Dashboard at http://localhost:7474/webadmin/ or data at http://localhost:7474/db/data/ ?

Please let me know in case you need any specific information to help me..

Thanks, Nitin.

Answer 1

For getting started with Neo4j Embedded and the Java API see:

http://docs.neo4j.org/chunked/milestone/tutorials-java-embedded.html

Getting correct counts of nodes and relationships:

IteratorUtil.count(GlobalGraphOperations.at(gdb).getAllNodes())
IteratorUtil.count(GlobalGraphOperations.at(gdb).getAllRelationships())

For accessing an embedded graph database with an integrated neo4j server, see http://docs.neo4j.org/chunked/milestone/server-embedded.html

Answer 2

Phewww! Those are a lot of questions for one entry...

To get the total number of nodes and relationships in your DB, use:

NodeManager nodeManager = ((GraphDatabaseAPI) graphDb).getDependencyResolver().resolveDependency(
            NodeManager.class);

long currentRelationships = nodeManager.getNumberOfIdsInUse(Relationship.class);
long currentNodes = nodeManager.getNumberOfIdsInUse(Node.class);

To change the path of the graph DB, simply pass the path to the GraphDatabaseFactory().newEmbeddedDatabase method. In the example you mentioned, you could simply set DB_PATH eg to /home/youruser/neo4j .

To access your DB with the webadmin, download neo4j, change the org.neo4j.server.database.location property in the file conf/neo4j-server.properties and point it to the path of your DB and launch the server.