无法在neo4j中的节点之间添加多个关系 [英] Cannot add more than one relationship between nodes in neo4j

问题描述

我正在尝试使用Neo4J建模社交网络.这要求一个用户可以与另一个用户具有多个关系.当我尝试保持这些关系时，只存储了一个.例如，这是我要做的测试单元:

I am trying to model a social network with Neo4J. This requires a user can have multiple relationships with another user. When I try to persist these relationships, only one is stored. For example, this is the test unit I do:

@Test
public void testFindConnections() {

    Id id1 = new Id();
    id1.setId("first-node");

    Id id2 = new Id();
    id2.setId("second-node");
    idService.save(id2);

    id1.connectedTo(id2, "first-rel");
    id1.connectedTo(id2, "second-rel");

    idService.save(id1);

    for (Id im : idService.findAll()) {
        System.out.println("-" + im.getId());
        if (im.getConnections().size() > 0) {
            for (ConnectionType ite : im.getConnections()) {
                System.out
                        .println("--" + ite.getId() + " " + ite.getType());
            }
        }
    }
}

这应该输出:

-first-node
--0 first-rel
--1 second-rel
-second-node
--0 first-rel
--1 second-rel

但是，它输出:

-first-node
--0 first-rel
-second-node
--0 first-rel

这是我的节点实体:

@NodeEntity
public class Id {

    @GraphId
    Long nodeId;
    @Indexed(unique = false)
    String id;

    @Fetch
    @RelatedToVia(direction=Direction.BOTH)
    Collection<ConnectionType> connections = new HashSet<ConnectionType>();
}

我的关系实体:

@RelationshipEntity(type = "CONNECTED_TO")
public class ConnectionType {

    @GraphId Long id;
    @StartNode Id fromUser;
    @EndNode Id toUser;

    String type;
}

可能是什么问题?还有其他方法可以对节点之间的几种关系进行建模吗?

What could the problem be? Is there any other way to model several relationships between nodes?

推荐答案

这不是Neo4j的缺点，它是Spring Data Neo4j的限制.

This is not a shortcoming of Neo4j, it is a restriction of Spring Data Neo4j.

通常，如果您具有不同类型的关系，那么也应该实际选择不同的关系类型，而不要为此使用关系属性.

Usually if you have different types of relationships it would make sense to actually choose different relationship-types too, and not use a relationship-property for this.

CONNECTED_TO也很通用.

Id还是一个很普通的类，不是User还是类似的东西?

Id is also a pretty generic class, shouldn't that be User or something similar?

FRIEND COLLEAGUE等会更有意义.

也就是说，如果您想保留自己的模型，则可以使用

That said, if you want to stay on your model you can either use

template.createRelationshipBetween(entity1,entity2,type,properties,true)

true表示允许重复.

对于两种类型的关系，也可以使用两种不同的目标类型，并使用

Alternatively use two different target types for the 2 types of relationships and use

@RelatedTo(enforceTargetType=true)

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