Neo4j的一個一對多取數據

Question

在我的春節，啓動/ Neo4j的應用程序，我有以下實體：

@NodeEntity 
public class User extends BaseEntity { 

    private static final String HAS = "HAS"; 

    @GraphId 
    private Long id; 

    private String username; 

    private String password; 

    private String email; 

    private String firstName; 

    private String lastName; 

    @RelatedTo(type = HAS, direction = Direction.OUTGOING) 
    private Set<Role> roles = new HashSet<Role>(); 

.... 

} 


@NodeEntity 
public class Vote extends BaseEntity { 

    private static final String VOTED_ON = "VOTED_ON"; 
    private final static String VOTED_FOR = "VOTED_FOR"; 
    private static final String CREATED_BY = "CREATED_BY"; 

    @GraphId 
    private Long id; 

    @RelatedTo(type = VOTED_FOR, direction = Direction.OUTGOING) 
    private Decision decision; 

    @RelatedTo(type = VOTED_ON, direction = Direction.OUTGOING) 
    private Criterion criteria; 

    @RelatedTo(type = CREATED_BY, direction = Direction.OUTGOING) 
    private User author; 

    private double weight; 

    private String description; 


} 

，我有以下SDN庫方法：

@Query("MATCH (d:Decision)<-[:VOTED_FOR]-(v:Vote)-[:VOTED_ON]->(c:Criterion) WHERE id(d) = {decisionId} AND id(c) = {criterionId} RETURN v") 
List<Vote> getVotes(@Param("decisionId") Long decisionId, @Param("criterionId") Long criterionId); 

在結果我有一個Vote的清單。

在客戶端上，我想顯示這些選票的列表，不僅包括用戶（作者）Id，還包括作者username。

如何獲取基於上述Vote.author.username和Vote.author.id查詢，並沒有獲取從User實體Vote實體相關聯的所有其他信息？無論如何，現在我只有Vote.author.id價值。

編輯：

以下查詢

@Query("MATCH (d:Decision)<-[:VOTED_FOR]-(v:Vote)-[:VOTED_ON]->(c:Criterion) WHERE id(d) = {decisionId} AND id(c) = {criterionId} WITH v, d, c MATCH v-[:CREATED_BY]->(u:User) RETURN {id: v.id, weight: v.weight, description: v.description, `decision.id` : d.id, `criterion.id` : c.id, `author.id`: u.id, `author.username`: u.username} as v") 
List<Vote> getVotesForDecisionOnCriterion(@Param("decisionId") Long decisionId, @Param("criterionId") Long criterionId); 

不與下面的異常工作：

org.springframework.dao.InvalidDataAccessApiUsageException: [Assertion failed] - entity is required; it must not be null 
    at org.springframework.data.neo4j.support.ParameterCheck.notNull(ParameterCheck.java:29) 
    at org.springframework.data.neo4j.support.Neo4jTemplate.projectTo(Neo4jTemplate.java:240) 
    at org.springframework.data.neo4j.support.conversion.EntityResultConverter.doConvert(EntityResultConverter.java:73) 
    at org.springframework.data.neo4j.conversion.DefaultConverter.convert(DefaultConverter.java:44) 
    at org.springframework.data.neo4j.support.conversion.EntityResultConverter.convert(EntityResultConverter.java:165) 
    at org.springframework.data.neo4j.conversion.QueryResultBuilder$1.underlyingObjectToObject(QueryResultBuilder.java:86) 

Answer 1

與DTO試試這個（也可以用干將接口）：

@QueryResult 
class VoteView { 
    String id; 
    Double weight; 
    String description; 
    String decisionId; 
    String criterionId; 
    String authorId; 
    String authorName; 
} 

@Query("MATCH (d:Decision)<-[:VOTED_FOR]-(v:Vote)-[:VOTED_ON]->(c:Criterion) WHERE id(d) = {decisionId} AND id(c) = {criterionId} WITH v, d, c MATCH v-[:CREATED_BY]->(u:User) RETURN {id: v.id, weight: v.weight, description: v.description, decisionId : d.id, criterionId : c.id, authorId: u.id, authorName: u.username} as v") 
List<VoteView> getVotesForDecisionOnCriterion(@Param("decisionId") Long decisionId, @Param("criterionId") Long criterionId); 

Answer 2

我不能與彈簧幫助，但不這樣做暗號得到你想要什麼？

MATCH (d:Decision)<-[:VOTED_FOR]-(v:Vote)-[:VOTED_ON]->(c:Criterion) 
WHERE id(d) = {decisionId} 
    AND id(c) = {criterionId} 
WITH v 
MATCH v-[:CREATED_BY]->(u:User) 
RETURN {id: v.id 
     , weight: v.weight 
     , `author.id`: u.id 
     , `author.username`: u.username 
     ... } as v