Can relate to only one element

Question

I am using Neo4j OGM 2.0.4 driver with Java. I have trouble with adding more than one relationship to element.

I do something like this:

Site site1 = new Site();
site1.setTitle("Site 1");
site1.setHtmlCode("Content of site 1");
Site site2 = new Site();

Site subsite1  = new Site();
subsite1.setTitle("Subsite 1");
subsite1.setHtmlCode("Content of subsite 1");
subsite1.setParent(site1);

Site subsite2  = new Site();
subsite2.setTitle("Subsite 2");
subsite2.setHtmlCode("Content of subsite 2");
subsite2.setParent(site1);

session.deleteAll(Site.class);

session.save(site1);

session.save(subsite1);
session.save(subsite2);

When I want to show all Site nodes (on localhost:7474) then "Subsite 1" has no relationship.

@NodeEntity
public class Site extends Entity
{
  private String _title;
  private String _htmlCode;

  @Relationship(type = "SITE_CREATED_BY")
  Author _author;

  @Relationship(type = "IS_CHILD")
  Set<Site> _parentSite;

  @Relationship(type = "IS_CHILD", direction = Relationship.INCOMING)
  Set<Site> _childSites;

  public Site()
  {
    _parentSite = new HashSet();
    _childSites = new HashSet();
  }

  public void setTitle(String title)
  {
    _title = title;
  }

  public String getTitle()
  {
    return _title;
  }

  public void setHtmlCode(String htmlCode)
  {
    _htmlCode = htmlCode;
  }

  public String getHtmlCode()
  {
    return _htmlCode;
  }

  public void setAuthor(Author author)
  {
    _author = author;
  }

  public void setParent(Site site)
  {
    _parentSite.add(site);
  }
}

Entity: public abstract class Entity { private Long id; private final ZonedDateTime _dateOfCreation;

  Entity()
  {
    _dateOfCreation = ZonedDateTime.now();
  }

  public Long getId()
  {
    return id;
  }

  public ZonedDateTime getDateOfCreation()
  {
    return _dateOfCreation;
  }

  @Override
  public boolean equals(Object o)
  {
    if (this == o) return true;
    if (o == null || id == null || getClass() != o.getClass()) return false;

    Entity entity = (Entity) o;

    return id.equals(entity.id);
  }

  @Override
  public int hashCode()
  {
    return (id == null) ? -1 : id.hashCode();
  }
}

What am I doing wrong?

Luanne Luanne · Accepted Answer · 2016-09-07T01:11:02

In this case where you have two relationships in different directions between the same type of node, first, make sure that you annotate both the fields as well as setter/accessor methods with the @Relationship,specifying the direction.

Site in your object model has references to both the parent and children, but when you create sites, they do not seem consistent with the model. Subsite1 and Subsite2 both set their parents to site1 but site has no record of its children (should be both subsites). Should work if your object and graph models are consistent.

Can relate to only one element

1 Answers