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;
    }

但是当我尝试使用以下内容找到之前保存的VoteGroup时

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

我的voteGroup.decision和voteGroup.criterion为空..

但如果我在findOne方法之后立即致电：

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

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

我的存储库方法/ Cypher有什么问题以及如何修复它？

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")

只返回VoteGroup节点，因此，这就是OGM可以映射的全部内容。如果您也想要决策和标准，那么您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")

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

BTW你共享的VoteGroup构造函数不会被OGM使用，你需要一个no-args构造函数。

Spring Data Neo4j返回带有空子节点

1 个答案: