Spring Data Neo4j 6: findAll() operation doesn't map relationships properly

[martin_lachance]

(same question was posted on StackOverflow 7 days ago: https://stackoverflow.com/questions/64859925/spring-data-neo4j-6-findall-operation-doesnt-map-relati...)

In Spring Data Neo4j 6 (6.0.1), a basic Neo4jTemplate findAll() operation with a simple relationship doesn't seem to map the relationship entity and its target even though they are part of the result set. Is this a bug or am I missing something?

Let's consider the following basic scenario:

var a = new EntityA();
var b = new EntityB();
a.entityB = b;

neo4jTemplate.save(a);

with

@Node
public class EntityA {
    @Id @GeneratedValue(UUIDStringGenerator.class)
    public String id;

    @Relationship("HAS_ENTITY_B")
    public EntityB entityB;
}

@Node
public class EntityB {
    @Id @GeneratedValue(UUIDStringGenerator.class)
    public String id;
}

When trying to map a result like this:

var result = neo4jTemplate.findAll("MATCH (a:EntityA)-[r:HAS_ENTITY_B]->(b:EntityB) RETURN a,r,b", EntityA.class);
Assert.notNull(result.get(0).entityB, "entityB should not be null here!");

I would expect the entityB property not to be null.

[gerrit_meier · Accepted solution]

The return part has to define the relationships and target nodes as lists.
So your query would be MATCH (a:EntityA)-[r:HAS_ENTITY_B]->(b:EntityB) RETURN a, collect(r), collect(b).
This is due to the fact, that SDN 6 expects to get the results for every EntityA within one record. If there would be more than one relationship (and/or EntityB related) Neo4j would return multiple records for the very same EntityA. This cannot get mapped a) in an immutable way and b) keep the reactive flow (if wanted) alive.

[martin_lachance]

Thank you Gerrit. With this modified query, it now works fine. Thanks for the info.