Spring Data Neo4j 返回具有空子节点的节点

Question

我有以下Spring Data Neo4j 4.2.0.BUILD-SNAPSHOT实体：

@NodeEntity
public class VoteGroup extends BaseEntity {
    private static final String VOTED_ON = "VOTED_ON";
    private final static String VOTED_FOR = "VOTED_FOR";
    @Relationship(type = VOTED_FOR, direction = Relationship.OUTGOING)
    private Decision decision;
    @Relationship(type = VOTED_ON, direction = Relationship.OUTGOING)
    private Criterion criterion;
...
}
@NodeEntity
public class Decision extends Commentable {
    @Relationship(type = VOTED_FOR, direction = Relationship.INCOMING)
    private Set<VoteGroup> voteGroups = new HashSet<>();
...
}
@NodeEntity
public class Criterion extends Authorable {
    @Relationship(type = VOTED_ON, direction = Relationship.INCOMING)
    private Set<VoteGroup> voteGroups = new HashSet<>();
....
}

存储 库：

@Repository
public interface VoteGroupRepository extends GraphRepository<VoteGroup> {
    @Query("MATCH (d:Decision)<-[:VOTED_FOR]-(vg:VoteGroup)-[:VOTED_ON]->(c:Criterion) WHERE id(d) = {decisionId} AND id(c) = {criterionId} RETURN vg")
    VoteGroup getVoteGroupForDecisionOnCriterion(@Param("decisionId") Long decisionId, @Param("criterionId") Long criterionId);
}

我正在使用以下构造函数创建VoteGroup：

public VoteGroup(Decision decision, Criterion criterion, double avgVotesWeight, long totalVotesCount) {
        this.decision = decision;
        decision.addVoteGroup(this);
        this.criterion = criterion;
        criterion.addVoteGroup(this);
        this.avgVotesWeight = avgVotesWeight;
        this.totalVotesCount = totalVotesCount;
    }

但是当我尝试通过以下方式查找以前保存的VoteGroup时：

VoteGroup voteGroup = getVoteGroupForDecisionOnCriterion(decision.getId(), criterion.getId());

我的voteGroup.decision和voteGroup.criterion为空。

但是如果我在那findOne方法之后立即调用：

voteGroup = voteGroupRepository.findOne(voteGroup.getId());

voteGroup.decision和voteGroup.criterion已正确填充。

我的存储库方法/密码有什么问题以及如何解决它？

Answer 1

查询

@Query("MATCH (d:Decision)<-[:VOTED_FOR]-(vg:VoteGroup)-[:VOTED_ON]->(c:Criterion) WHERE id(d) = {decisionId} AND id(c) = {criterionId} RETURN vg")

仅返回 VoteGroup 节点，因此，这就是 OGM 可以映射的全部内容。如果你也想要决策和标准，那么你必须返回这些节点及其关系。这样的事情应该有效：

@Query("MATCH (d:Decision)<-[for:VOTED_FOR]-(vg:VoteGroup)-[on:VOTED_ON]->(c:Criterion) WHERE id(d) = {decisionId} AND id(c) = {criterionId} RETURN vg,d,for,on,c")

这篇博文包含更多示例： http://graphaware.com/neo4j/2016/04/06/mapping-query-entities-sdn.html

顺便说一句，您共享的 VoteGroup 构造函数不会被 OGM 使用，您需要一个无参数构造函数。