我正在尝试将 TraversalDescription.traverse() 的结果映射到自定义节点和关系对象的列表。
如果我将 Cypher 与 sdn 一起使用,我可以执行以下操作:
@Query("WITH {0} AS ns, {1} AS ne " +
"MATCH p=(n1{name:ns})-[*]-(n), (n2{name:ne}) " +
"WHERE n=n2 " +
"AND all(a IN nodes(p) WHERE single(x IN nodes(p) WHERE x=a)) " +
"RETURN nodes(p) as persons, rels(p) as connections " +
"ORDER BY size(nodes(p))")
List<GraphPath> getAllPaths(String startNode, String endNode);
然后映射到包含自定义节点和关系对象的 GraphPath 对象:
图形路径.java
@Getter
@Setter
@ToString
@NoArgsConstructor
@AllArgsConstructor
@QueryResult
public class GraphPath {
private List<Person> persons;
private List<Connection> connections;
}
Person.java
@Getter
@Setter
@NoArgsConstructor
@NodeEntity(label = "Person")
public class Person extends Entity{
@Property(name = "name")
private String fullName;
@Property(name = "status")
private String status;
@Relationship(type = "CONNECTS", direction = Relationship.UNDIRECTED)
private Set<Connection> personConnections = new HashSet<>();
}
连接.java
@Getter
@Setter
@NoArgsConstructor
@RelationshipEntity(type = "CONNECTS")
public class Connection extends Entity{
@Property(name="connection_id")
private String connectId;
@Property(name = "status")
private String status;
@StartNode
private Person personSource;
@EndNode
private Person personTarget;
}
而 Entity.java 只是具有字段 id 和覆盖的 equals() 和 hashCode() 的 POJO
这在简单的图形中运行良好,但当图形变得更复杂时,获得结果的时间会增加更多。我的目标是找到起始节点和结束节点之间的所有可能路径,并且每条路径中没有重复的节点或关系。我希望使用遍历 API 来消除运行中一些不需要的路径(包含重复节点或关系的路径),以减少处理时间。
这是我使用的代码,graphDb 只是 GraphDatabaseService:
final Node startNode = graphDb.findNode(Labels.Person, "name", startNodeName);
final Node endNode = graphDb.findNode(Labels.Person, "name", endNodeName);
TraversalDescription td = graphDb.traversalDescription()
.depthFirst()
.evaluator(Evaluators.excludeStartPosition())
.evaluator(Evaluators.includeWhereEndNodeIs(endNode))
.relationships(Types.CONNECTS)
.uniqueness(Uniqueness.NODE_PATH)
.uniqueness(Uniqueness.RELATIONSHIP_PATH);
Traverser t = td.traverse(startNode)
现在的问题是,我怎样才能将结果映射到我上面提到的自定义对象?手动执行会导致我必须处理递归对象映射( Person 中的 Connection,以及 Connection 中的目标和源 Person)。
最佳答案
正如我在评论中所写,我想我会手动进行映射,因为 Traverser
返回的 Path
已经包含节点和关系,并且只有现在需要读取属性。
通过在 Path
上迭代,可以构建 GraphPath
及其 Person
和 Connection
依次完成。这段代码显然可以通过提取方法进行重构。
for (Path path : t) {
GraphPath gp = new GraphPath();
Person person = null;
Connection connection = null;
for (PropertyContainer pc : path) {
if (pc instanceof Node) {
Node node = (Node) pc;
person = new Person();
person.setId(node.getId());
person.setFullName(node.getProperty("name", null));
person.setStatus(node.getProperty("status", null));
gp.getPersons().add(person);
// No connection exists for the first node in the path
if (connection != null) {
// Find out which end has already been connected
if (connection.getPersonSource() == null) {
connection.setPersonSource(person);
} else {
connection.setPersonTarget(person);
}
person.getPersonConnections().add(connection);
}
} else {
Relationship rel = (Relationship) pc;
connection = new Connection();
connection.setId(rel.getId());
connection.setConnectId(rel.getProperty("connection_id", null));
connection.setStatus(rel.getProperty("status", null));
gp.getConnections().add(connection);
// Find out which end has already been mapped
if (rel.getStartNode().getId() == person.getId().longValue()) {
connection.setPersonSource(person);
} else {
connection.setPersonTarget(person);
}
person.getPersonConnections().add(connection);
}
}
}
如果您想要给定节点的单个Person
(resp. Connection
)实例,您可以更改Person
(resp. Connection
) 创建以首先查找 Map
,您将在其中按 id 索引实体;您还必须一起更改 Person
和 Connection
的接线,以仅在 Connection
上设置未设置的端点,而不依赖于一端或另一端仍然无效的事实。
关于java - Neo4j java遍历api对象映射,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38341546/