Generic abstract RelationshipEntity not working

[nicoruti]

I started looking at Neo4j today and am now running some tests with OGM. The library is really awesome, thanks for your work! However, when playing around with model abstractions, I encountered the following setup which throws an exception:

@NodeEntity
public class A {
   @GraphId
   private Long id;
   @Relationship(type = "R", direction = Relationship.OUTGOING)
   public R r;
}

@NodeEntity
public class B {
   @GraphId
   private Long id;
   @Relationship(type = "R", direction = Relationship.INCOMING)
   public R r;
}

// Generic base class for relationships
public class BaseR<S, T> {
   @GraphId
   private Long id;
   @StartNode
   private S fromNode;
   @EndNode
   private T toNode;

   protected BaseR(S fromNode, T toNode) {
      this.fromNode = fromNode;
      this.toNode = toNode;
   }
}

@RelationshipEntity
public class R extends BaseR<A, B> {
   public R(A fromNode, B toNode) {
      super(fromNode, toNode);
   }
}

The code I test with is

   @Test
   public void testUsingAbstractRelationShip() {      
      A a = new A();
      session.save(a);

      B b = new B();
      session.save(b);

      R r = new R(a, b);
      a.r = r;
      b.r = r;

      session.save(a); // --> throws exception below
   }

And here comes the exception:

java.lang.RuntimeException: @StartNode of a relationship entity may not be null
    at org.neo4j.ogm.mapper.EntityGraphMapper.getStartEntity(EntityGraphMapper.java:510)
    at org.neo4j.ogm.mapper.EntityGraphMapper.haveRelationEndsChanged(EntityGraphMapper.java:390)
    at org.neo4j.ogm.mapper.EntityGraphMapper.getRelationshipBuilder(EntityGraphMapper.java:363)
    at org.neo4j.ogm.mapper.EntityGraphMapper.link(EntityGraphMapper.java:326)
    at org.neo4j.ogm.mapper.EntityGraphMapper.mapEntityReferences(EntityGraphMapper.java:277)
    at org.neo4j.ogm.mapper.EntityGraphMapper.mapEntity(EntityGraphMapper.java:158)
    at org.neo4j.ogm.mapper.EntityGraphMapper.map(EntityGraphMapper.java:91)
    at org.neo4j.ogm.session.delegates.SaveDelegate.save(SaveDelegate.java:67)
    at org.neo4j.ogm.session.delegates.SaveDelegate.save(SaveDelegate.java:43)
    at org.neo4j.ogm.session.Neo4jSession.save(Neo4jSession.java:386)
    at .a.b.c.GenericTypesTest.testUsingAbstractRelationShip(GenericTypesTest.java:40)

It's interesting, as the base class without the generic types S and T does work as expected (although this breaks the reusability of the base relationship entity):

public class BaseR {
   @GraphId
   private Long id;
   @StartNode
   private A fromNode;
   @EndNode
   private B toNode;

   protected BaseR(A fromNode, B toNode) {
      this.fromNode = fromNode;
      this.toNode = toNode;
   }
}

@RelationshipEntity
public class R extends BaseR {
   public R(A fromNode, B toNode) {
      super(fromNode, toNode);
   }
}

[nicoruti]

As soon as published, the following workaround came to my mind: Use another base class (or interface) for the NodeEntities and code against them. This removes the need for generics. Here's a working example:

// Base Entity class
public class BaseE {
   @GraphId
   private Long id;
}

@NodeEntity
public class A extends BaseE {
   @Relationship(type = "R", direction = Relationship.OUTGOING)
   public R r;
}

@NodeEntity
public class B extends BaseE {
   @Relationship(type = "R", direction = Relationship.INCOMING)
   public R r;
}

public abstract class BaseR {
   @GraphId
   private Long id;
   @StartNode
   private BaseE fromNode;
   @EndNode
   private BaseE toNode;

   protected BaseR(BaseE fromNode, BaseE toNode) {
      this.fromNode = fromNode;
      this.toNode = toNode;
   }
}

@RelationshipEntity
public class R extends BaseR {
   public R(A fromNode, B toNode) {
      super(fromNode, toNode);
   }
}

[vince-bickers]

Fixed in 2.0.0-SNAPSHOT

[ghost]

I'm using version 2.0.3, and I'm still getting this exception on generic relations.

Classes example

public class RelationEntity<O,T> {
    @GraphId
    public Long id;

    @StartNode
    public O orign;

    @EndNode
    public T target;

    @DateLong
    public Date createdAt;

}

@RelationshipEntity(type = "OWNS")
public class Owns<T> extends RelationEntity<User,T> {
    public Boolean isProfile;
}

java.lang.RuntimeException: @startnode of a relationship entity may not be null
at org.neo4j.ogm.context.EntityGraphMapper.getStartEntity(EntityGraphMapper.java:611)
at org.neo4j.ogm.context.EntityGraphMapper.haveRelationEndsChanged(EntityGraphMapper.java:476)
at org.neo4j.ogm.context.EntityGraphMapper.getRelationshipBuilder(EntityGraphMapper.java:444)
at org.neo4j.ogm.context.EntityGraphMapper.link(EntityGraphMapper.java:406)
at org.neo4j.ogm.context.EntityGraphMapper.mapEntityReferences(EntityGraphMapper.java:337)
at org.neo4j.ogm.context.EntityGraphMapper.mapEntity(EntityGraphMapper.java:207)
at org.neo4j.ogm.context.EntityGraphMapper.map(EntityGraphMapper.java:133)
at org.neo4j.ogm.session.delegates.SaveDelegate.save(SaveDelegate.java:69)
at org.neo4j.ogm.session.Neo4jSession.save(Neo4jSession.java:369)

[mangrish]

This is still broken. Reopening.

[frant-hartm]

Fixed in master (for 3.0.0 release).

It still won't work for

class Owns<T> extends RelationEntity<User,T> 

use cases, but should work for

class Owns extends RelationEntity<User, User>

We use the types in query generation so this can't be (at the moment) completely generic.