User defined function: Failed to invoke function Caused by: java.lang.NoSuchMethodError

[ruko]

Hello,
I am playing around with the plugin system of neo4j.
I just want to call my function with an ID and want the neighbours of this node returned as a String:

public class Neighbours {
    @Context
    public GraphDatabaseService db;

    @UserFunction
    public String neighbours(@Name("nodeId") long nodeId) {
        Node node = db.findNode(Label.label(""), "id", nodeId);
        return StreamSupport.stream(node.getRelationships().spliterator(), false)
                .map(neighbourNode -> neighbourNode.getProperty("id").toString())
                .collect(Collectors.joining(", "));
    }
}

Calling my function causes this error:

Neo.ClientError.Procedure.ProcedureCallFailed
Failed to invoke function `example.neighbours`: Caused by: java.lang.NoSuchMethodError: org.neo4j.graphdb.GraphDatabaseService.findNode(Lorg/neo4j/graphdb/Label;Ljava/lang/String;Ljava/lang/Object;)Lorg/neo4j/graphdb/Node;

I also tried other methods of GraphDatabaseService, no luck.
What is wrong with my function? I am using neo4j-community-4.0.4.

Also I do not have any labels on my nodes. Would my above implementation work to retrive my label-less nodes or do I have to use null as parameter?

//edit: ok, seems like the procedure-template on github ist for neo4j 3.x and I am using 4.x.
Is there any documentation on how to do this in the newer Neo4j?

[mark_needham]

We need to fix the lack of procedure template!In the meantime, you can find some example in Max De Marzi's blog:

Max De Marzi – 17 Apr 20

Stored Procedures in Neo4j Are NOT Evil

Some of you may be too young to remember this, but writing your application logic in Stored Procedures was all the rage back in the day (PG devs you wouldn’t understand). That is mostly becau…

[ruko]

I had to update the version numbers in the pom.xml and first begin a transaction.
Now I can call findNode on the transaction object to retrieve a node.
But I cannot figure out how to find a node which does not have a label present.

Node node = tx.findNode(Label.label(""), "id", nodeId);

This does not return any node. I also tried with * as label and with null (which causes a NPE), but nothing works.

[anthapu]

Node node = tx.findNode(Label.label(""), "id", nodeId);

This method is trying to find using property named "id". This is similar to

MATCH (n) where n.id=nodeId

I don't think that is correct way to retrieve node by it's node id.

Can you try

Node node = tx.getNodeById​(nodeId)

This will retrieve the node by it's nodeId.

[mark_needham]

I think you may have to find the node via the tx.getAllNodes() function and then check the property on each node until you find the one you want.