java - RelationshipEntity 未保留

Question

我的关系有问题

@RelationshipEntity(type = RelTypes.Tag.TAG_ON_OBJECT_EVALUATION)
public class TagOnObjectEvaluation
{
  @StartNode
  private Mashup taggableObject;

  @EndNode
  private Tag tag;

  // Other fields, getters and setters
}

在涉及的两个实体(Mashup 和Tag)中，我都有这个字段(方向相反)

@RelatedToVia(type = RelTypes.Tag.TAG_ON_OBJECT_EVALUATION,
      direction = Direction.INCOMING /*Direction.OUTGOING*/)
  private Set<TagOnObjectEvaluation> tagOnObjectEvaluations =
      new HashSet<TagOnObjectEvaluation>();

然后，我有各种服务类来管理Tag、Mashup 和TagOnObjectEvaluation。现在测试的类是后者。注意:名称有点困惑，它是以前的编码器遗留下来的，您可以阅读 DAO as Service。此外，GenericNeo4jDAOImpl(同样，将其读作 GenericServiceNeo4jImpl)简单地定义了实体管理的标准方法(create()、find()、update() , delete(), fetch() )

@Service
public class TagOnObjectEvaluationDAONeo4jImpl extends
    GenericNeo4jDAOImpl<TagOnObjectEvaluation> implements
    TagOnObjectEvaluationDAO
{
  @Autowired
  private TagOnObjectEvaluationRepository repository;

  public TagOnObjectEvaluationDAONeo4jImpl()
  {
    super(TagOnObjectEvaluation.class);
  }

  public TagOnObjectEvaluationDAONeo4jImpl(
      Class<? extends TagOnObjectEvaluation> entityClass)
  {
    super(entityClass);
  }

  @Override
  public TagOnObjectEvaluation create(TagOnObjectEvaluation t)
  {
    Transaction tx = template.getGraphDatabaseService().beginTx();
    TagOnObjectEvaluation savedT = null;
    try
    {
      // This is to enforce the uniqueness of the relationship. I know it can fail in many ways, but this is not a problem ATM 
      savedT =
          template.getRelationshipBetween(
              t.getTaggableObject(), t.getTag(),
              TagOnObjectEvaluation.class,
              RelTypes.Tag.TAG_ON_OBJECT_EVALUATION);
      if (savedT == null)
        savedT = super.create(t);
      tx.success();
    }
    catch (Exception e)
    {
      tx.failure();
      savedT = null;
    }
    finally
    {
      tx.finish();
    }
    return savedT;
  }
}

到目前为止，它看起来非常简单。但是当我尝试保留一个 RelationshipEntity 实例时，我遇到了很多问题。

  @Test
  public void testRelationshipEntityWasPersisted()
  {
    TagOnObjectEvaluation tagOnObjectEvaluation = new TagOnObjectEvaluation(taggedObject, tag);

    tagOnObjectEvaluationDao.create(tagOnObjectEvaluation);
    assertNotNull(tagOnObjectEvaluation.getId());
    LOGGER.info("TagOnObjectEvaluation id = " + tagOnObjectEvaluation.getId());

    tagDao.fetch(tag);
    assertEquals(1, tag.getTaggedObjectsEvaluations().size());
  }

上次测试失败:大小为 0 而不是 1。此外，尽管看起来实体已正确存储(它分配了一个 id)，但如果我稍后导航数据库根本没有它的踪迹。我还尝试使用相关节点集以不同的方式添加关系； f.e.

tag.getTaggedObjectsEvaluations().add(tagOnObjectEvaluation);
tagDao.update(tag); 

但一点改进都没有。

Answer 1

你需要在你的实体Mashape中改变关系的方向，(实体对应于你的的@StartNode @RelationshipEntity TagOnObjectEvaluation).

@NodeEntity
class Mashape {

   // ...
   @RelatedToVia(type = RelTypes.Tag.TAG_ON_OBJECT_EVALUATION, direction = Direction.OUTGOING)
   private Set<TagOnObjectEvaluation> tagOnObjectEvaluations = new HashSet<TagOnObjectEvaluation>();    

}

就根据specifications点那个@RelatedToVia spring-data-neo4j注解的方向默认是OUTGOING，所以你真的不需要指定方向这个案例。这也应该是正确的:

   @RelatedToVia(type = RelTypes.Tag.TAG_ON_OBJECT_EVALUATION)
   private Set<TagOnObjectEvaluation> tagOnObjectEvaluations = new HashSet<TagOnObjectEvaluation>();    

希望对您有所帮助。