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I am trying to build the following scenario using Neo4J SDN. There is an entity Person who has a list of Item entities. Each Item entity can have one or more child Items. I wish to have bidirectional relationships between a Person and the list of Items and another bidirectional relationship between Parent Item and Child Items. Till now, a parent Item can have a list of another set of child Items but each of the child items does not have any children under it.

I have tried to build the domain objects and relationships as 

@NodeEntity
public class Person {

    @GraphId 
    private Long id;
    private String name;
    private String email;
    @Relationship(type = "ITEM_CREATED_BY",direction = Relationship.INCOMING)
    List<PersonItemRelation> personItemRelations = new ArrayList<PersonItemRelation>();
}


@NodeEntity
public class Item {

    @GraphId
    Long id;
    String uuid;
    String name;
    @Relationship(type = "ITEM_CREATED_BY",direction = Relationship.OUTGOING)
    private PersonItemRelation personItemRelation ;
    @Relationship(type = "IS_CHILD_ITEM_OF",direction = Relationship.OUTGOING)
    private ItemParentChildRelation parentItemRelation;
    @Relationship(type = "IS_CHILD_ITEM_OF",direction = Relationship.INCOMING)
    private List<ItemParentChildRelation> subItemRelations = new ArrayList<ItemParentChildRelation>();
}

@RelationshipEntity(type = "IS_CHILD_ITEM_OF")
public class ItemParentChildRelation {

    @GraphId
    Long id;
    @DateLong
    Date creationDate;
    @StartNode
    Item childItem;
    @EndNode
    Item parentItem;
}


@RelationshipEntity(type = "ITEM_CREATED_BY")
public class PersonItemRelation implements Serializable {

    @GraphId
    Long id;
    @Property
    String uuid;
    @StartNode
    Item item;
    @EndNode
    Person person;
    @Property
    String status;
    @DateLong
    Date date;
}

All of the above entities have required getters and setters with proper annotations as well.

My first question is, is this the right way of implementing the model.

If so, I am facing some problems with it. If I want to update a subItem (ie an Item which is a child of a parent Item), then sometimes, the relation between the parent Item and the child Item is lost.

The way I performed the update is given below

public void deactivateItem(String itemUuid){
    Item item=itemRepository.findActiveByUuid(itemUuid);
    if(item != null){
        item.setStatus("INACTIVE");
        itemRepository.saveItem(item);
    }
}

The function findActiveByUuid(String itemUuid) is implemented in ItemRepository as 

@Query("MATCH (p:Item {status:'ACTIVE'}) "
        + "where "
        + "(p.uuid={0}) "
        + "return p")
Item findActiveByUuid(String uuid);

One more thing which I noticed was that if I am fetching data using cypher, as indicated above, the depth of the query is 0. This is indicated by the fact when I am trying to get the size of subItemRelations from the Item object, the result is zero.

But if I am fetching using spring-data built-in functions like 

Item findByUuid(String uuid);

then the size of subItemRelations is coming correctly (>0 in cases where an Item has one or more child Items)

I am using spring-data-neo4j 4.1.2.RELEASE and Neo4J 3.0.3 Community Edition

Luanne
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Soumya
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  • If you load the item to modify using findByUuid(String uuid) and then modify the status and save, do you lose relationships? – Luanne Jul 16 '16 at 02:59
  • I lost the relationships in both cases, findByUuid(String uuid) and findActiveByUuid(String uuid). But the strange thing is, since your post, I have been trying to reproduce the problem with the same test cases that I was running yesterday using both of the above. But the problem of losing relationships did not occur even once although it was quite frequent at the time I wrote the post – Soumya Jul 16 '16 at 07:15

0 Answers0