Get Nodes from Embedded Neo4j

[Doktor_DOOM]

Hi,

complete new in this topic. I got a project wich creates a Java Neo4j db. With the folder data, logs and sub folder database and transactions.  These Project is using the 4.* Neo4j Libraries to store the data. With this mentioned dependencies, im searching for a possibility to get the connection to this stored db and get a Node from there. 

[glilienfield]

This reference should help:

https://neo4j.com/docs/java-reference/current/java-embedded/

the hello world section has example code showing you how to access the database.  

https://neo4j.com/docs/java-reference/current/java-embedded/hello-world/

[Doktor_DOOM]

Hi @glilienfield,

i will try this approach tomorrow. At the moment i have some doubts regarding this hello world example. Because this examples is related to the newest Neo4j SW Version.  And my stored Neo4j db is created with version 4.*. 

[glilienfield]

I use version 4 of the Java API. The hello world looks good.  You can also change the version of the document to the version you are during.  There is a drop down menu within the icon at the top left. 

[Doktor_DOOM]

Hi @glilienfield,

i forgot one question. Is it possible to open this stored db with the neo4j desktop version? 

[glilienfield]

check this out:

https://neo4j.com/docs/java-reference/current/java-embedded/bolt/

once you have enabled the bolt protocol and your application is running, you can create a ‘remote connection’ in neo4j desk or to connect to your embedded server. 

[Doktor_DOOM]

Hi @glilienfield,

i tried three approaches to get the nodes from the embedded neo4j.

String db_path = System.getProperty("user.dir") + "/cooccsdatabase";
File database = new File(db_path);
		
managementService = new DatabaseManagementServiceBuilder(database).build();
graphDB = managementService.database(DEFAULT_DATABASE_NAME);

try ( Transaction tx = graphDB.beginTx();
				
Result result = tx.execute( "MATCH (n {name: 'Secure'}) RETURN n, n.name" ) )
			{
			    while ( result.hasNext() )
			    {
			        Map<String,Object> row = result.next();
			        String rows = "";
					for ( Entry<String, Object> column : row.entrySet() )
			        {
			            rows += column.getKey() + ": " + column.getValue() + "; ";
			        }
			        rows += "\n";
			    }
			}

 Results from the first approach are null.  

With the second approach, i got an exception from the Driver.

Could not instrument class org/neo4j/driver/Driver: Unsupported class file major version 61.

String db_path = System.getProperty("user.dir") + "/cooccsdatabase";
File database = new File(db_path);
		
managementService = new DatabaseManagementServiceBuilder(database).build();
graphDB = managementService.database(DEFAULT_DATABASE_NAME);

		try (Session session = driver.session()) {
	        return session.executeRead(tx -> {
	            List<String> names = new ArrayList<>();
	            //var result = tx.run("Match (n:Person{name: 'Tom Hanks'})-[r]->(m) Return m.title"); // Tom Hanks ist das gesuchte schlüssel wort
	            org.neo4j.driver.Result result = tx.run("MATCH (node:Person) WHERE node.name = 'Secure' RETURN node"); // Tom Hanks ist das gesuchte schlüssel wort
	            while (result.hasNext()) {
	                names.add(result.next().get(0).asString());
	            }
	            return names;
	        });
	    }

With the third one, i got the same exception. 

Could not instrument class org/neo4j/driver/Driver: Unsupported class file major version 61.

String db_path = System.getProperty("user.dir") + "/cooccsdatabase";
File database = new File(db_path);
		
managementService = new DatabaseManagementServiceBuilder(database).build();
graphDB = managementService.database(DEFAULT_DATABASE_NAME);
		
		try (Session session = driver.session()) {
		      return session.readTransaction(tx -> tx.run(
		                      "optional match(n:Person{name: $Node}) " +
		                              "return size(collect(distinct n)) > 0 as isExists", Map.of("person", Node))
		              .single().get("isExists").asBoolean());
		    }

[glilienfield]

Did you create the node you are looking for before your query?  If not, use createNode method on the transaction to create a node.  

I try to use the API as much as possible to retrieve/create nodes and traverse the graph. at this level you are working directly with the graph entities, i.e., nodes and relationships. I use execute only when executing complex cypher queries. 

You can use the findNode method on the transaction to find a node directly. Then you can use the getRelationships method on the node to traverse graphs. 

https://neo4j.com/docs/java-reference/5/javadocs/org/neo4j/graphdb/Transaction.html

https://neo4j.com/docs/java-reference/5/javadocs/org/neo4j/graphdb/Node.html

[glilienfield · Accepted solution]

Just a note, you would not use the driver to execute queries against your embedded server from within the same application. You would use the 'execute' method on a transaction. This is what you did in the first query.

I do use the driver in my test code when I want to test a custom procedure or function I built works properly when accessed remotely through a query, as it will be used in my application.  

[Doktor_DOOM]

Hi @glilienfield,

this find method was a well solution. Thanks