CODEWITHSUNDEEP
javaneo4jspring-data-neo4jspring-data-neo4j-4
Xipo
Xipo

Reputation: 1823

Persist a RelationshipEntity that is not a NodeEntity property

In SDN4 I wish to persist a @RelationshipEntity which is not a @NodeEntity's property. Example:

@NodeEntity
public class User{
    Long id;
}

@RelationshipEntity(type="FOLLOWS")
public class Follows{
    @GraphId   private Long relationshipId;
    @StartNode private User follower;
    @EndNode   private User followee;
    @Property  private Date from;

    public Follows(){}
    public Follows(User u1, User u2){
         this.follower = u1;
         this.followee = u2;
    }
}

@Repository
interface FollowsRepository extends GraphRepository<Follows>{}

And then persist the Follows @Relationship like this

...
followsRepository.save(new Follows(user1, user2));
...

But when doing so, the Relationship is not persisted!!

Sadly as stated in the accepted answer this cannot (yet) be done (SDN 4.0.0.RELEASE)

Workaround 1

It is possible to persist @RelationshipEntities using @Query in GraphRepositories. 

@Query("Match (a:User), (b:User) WHERE id(a) = {0} 
                     AND id(b) = {1} CREATE (a)-[r:FOLLOWS {date:{2}}]->(b) RETURN r ")

Workaround 2

This can also be done by treating Follows as a @NodeEntity, which might not be the most performant thing to do BUT will not affect any of the @NodeEntities of the domain, nor the service layer AND you won't have to mess with the depth factor when loading and persisting entities

@NodeEntity
public class User{
    Long id;
}

@NodeEntity
public class Follows{
    private Long Id;
    @Relationship(type="FOLLOWER")
    private User follower;
    @Relationship(type="FOLLOWEE")
    private User followee;
    private Date from;

    public Follows(){}
    public Follows(User u1, User u2){
         this.follower = u1;
         this.followee = u2;
    }
}

....
//Placed in userService
Follows createFollowsRelationship(User u1, User u2){
   return followsRepository.save(new Follows(user1, user2));
}
.....

Upvotes: 1

Views: 243

Answers (1)

Luanne
Luanne

Reputation: 19373

At the moment, you cannot persist a relationship entity directly when it is not referenced from participating node entities. You'll have to save the start node and make sure it has a reference to the relationship entity.

There will be some enhancements around how relationship entities are persisted but not in the next release.

Upvotes: 3

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