Map instead of Set for relationship in Neo4j OGM

Question

In the Neo4j OGM tutorial, I see that only Set have been used for mapping relationships. Is it possible to use a map ?

Consider the following example

Suppose I have a class as follows:

 @NodeEntity
    public class Person {
     @Property
       String idCardNumber;

        Map <String, Car> cars;
    }

    @NodeEntity
    public class Car{
      @Id
       String plateNumber;
        @Property
       String color;
    }

How to define a relationship from the class Person and Car given the it's a map that is being used in the class Person ?

Answer 1

This is not possible because there is no way to store the additional information (e.g. the String in your example) in the database. I would argue that there is no need for a Map structure for relationships at all because they are always defined by their type or the rich relationship entity via @RelationshipEntity.

Answer 2

As mentioned by @meistermeier, this is not directly possible. But I uses a hack as in my case what i only need is to be able to persist the object directly in the database using Neo4j OGM. In short, i use a set and put the objects in it just before persisting the an instance of class Person. The codes are available below:

@NodeEntity
    public class Person {
     @Property
       String idCardNumber;

        @Transient
        Map <String, Car> cars;

        @Relationship(type = "hasCar",direction = Relationship.OUTGOING)
        Set <Car> finalCars;

        public void beforeSave(){
                 finalCars = new HashSet<>(cars.values());
         }
    }

    @NodeEntity
    public class Car{
      @Id
       String plateNumber;
        @Property
       String color;
    }

Then, just before saving the Person object in the database, the cars are loaded in the set finalCars. This can be done directly in the method responsible for persisting a Person by calling beforeSave() on the insatance.