java - 遍历器关系方向顺序neo4j java

Question

我想遍历具有相同关系的图，但首先是传出关系，其次是传入关系(按此特定顺序)。我发现了

    traverse(Traverser.Order traversalOrder, 
StopEvaluator stopEvaluator,ReturnableEvaluator returnableEvaluator, 
RelationshipType firstRelationshipType,Direction firstDirection, 
RelationshipType secondRelationshipType,Direction secondDirection)

我还没有找到任何关于如何填充字段 traversalOrder stopEvaluator、returnableEvaluator 的示例

我的示例代码是:

for (Path position : graphDb.traversalDescription()
            .relationships(Wikilections_user.RelTypes.Voted, Direction.OUTGOING)
            .relationships(Wikilections_user.RelTypes.Voted, Direction.INCOMING)
            .evaluator(Evaluators.fromDepth(1))
            .evaluator(Evaluators.toDepth(2))
            .evaluator(Evaluators.includeWhereEndNodeIs(node2))
            .uniqueness(Uniqueness.RELATIONSHIP_PATH)
            //.evaluator(Evaluators.excludeStartPosition())
            .traverse(node1)) {

我想更改 .traverse(node1)) 部分，以便仅返回首先遇到传出关系，然后遇到传入关系的路径。这怎么可能？

Answer 1

对于更复杂的行为，您可以使用 TraversalDescription.expand() 提供自定义 PathExpander 。伪实现可能如下所示:

class MyPathExpander implements PathExpander {
   Iterable<Relationship> expand(Path path, BranchState state) {
      switch (path.length()) {
         case 0:
          return path.endNode().getRelationships(Wikilections_user.RelTypes.Voted, Direction.OUTGOING);
         case 1:
          return path.endNode().getRelationships(Wikilections_user.RelTypes.Voted, Direction.INCOMING)
         default: 
             return Iterables.empty();

      }
   }
}