Java 如何使用cypher迭代具有多个值的列？

我试过的代码是

    firstNode = graphDb.createNode();//creating nodes like this
    firstNode.setProperty( "person", "Andy " ); 
    Label myLabel = DynamicLabel.label("person");
    firstNode.addLabel(myLabel); ...

    relationship = firstNode.createRelationshipTo( secondNode, RelTypes.emails );// creating relationships like this
    relationship.setProperty( "relationship", "email " );....


    Transaction tx1 = graphDb.beginTx();
    try{
        ExecutionEngine engine = new ExecutionEngine(graphDb);

        ExecutionResult result = engine.execute("MATCH (sender:person)-[:emails]-(receiver) RETURN sender,  count(receiver)as count, collect(receiver) as receivers ORDER BY count DESC ");..

我得到的结果是：

 sender                  | count | receivers                                                                 
Node[2]{person:"Chris"} | 3     | [Node[4]{person:"Elsa "},Node[0]{person:"Andy "},Node[1]{person:"Bobby"}] 
Node[4]{person:"Elsa "} | 3     | [Node[5]{person:"Frank"},Node[2]{person:"Chris"},Node[3]{person:"David"}]
Node[1]{person:"Bobby"} | 3     | [Node[2]{person:"Chris"},Node[3]{person:"David"},Node[0]{person:"Andy "}]
Node[5]{person:"Frank"} | 2     | [Node[3]{person:"David"},Node[4]{person:"Elsa "}

我想迭代接收器。因此，我尝试了以下方法：

for (Map<String,Object> row : result) {
               Node x = (Node)row.get("receivers");
               System.out.println(x);

               for (String prop : x.getPropertyKeys()) {
                  System.out.println(prop +": "+x.getProperty(prop));

               }

for（映射行：结果）{
Node x=（Node）row.get（“接收者”）；
系统输出println（x）；
对于（字符串属性：x.getPropertyKeys（））{
System.out.println（prop+“：”+x.getProperty（prop））；
}

但它在线程“main”java.lang.ClassCastException中引发异常：scala.collection.convert.Wrappers$SeqWrapper不能强制转换为org.neo4j.graphdb.Node

---

如何执行此操作？

问题在于，在cypher查询中，您将receiver.person属性收集到一个名为receivers的数组中。receivers不是一个节点，而是一个属性数组。您不能将其转换为字符串。如果您希望获得实际的receiver节点，则需要将查询语句更改为：

MATCH (sender:person)-[:emails]-(receiver) RETURN sender, count(receiver)as count, receiver as receivers ORDER BY count DESC

或者，如果要使用属性数组，则可以执行类似以下代码的操作：

Object receivers = row.get("receivers")
if(receivers instanceof String[]) {
  for(String receiver in receivers) {
    .. do something
  }
} else {
  // do something with receiver as a single string value
}

显然，如果不是字符串，您需要将接收器的类型从字符串更改为适当的类型。

这是一件简单的事情

try{
        ExecutionEngine engine = new ExecutionEngine(graphDb);

        ExecutionResult result = engine.execute("MATCH (sender:person)-[:emails]-(receiver) RETURN sender,  count(receiver)as count, collect(receiver.person) as receivers ORDER BY count DESC ");
        //ExecutionResult result = engine.execute("MATCH (sender:person)-[:emails]->(receiver)  WITH sender, collect(receiver.person) as receivers, RETURN {sender: sender.person,  receivers: receivers) ORDER BY size(receivers) DESC");
        //System.out.println(result.dumpToString());
        LinkedList list_prop = new LinkedList();

        for (Map<String,Object> row : result) {
            Node x = (Node)row.get("sender");
            Object y = row.get("receivers");
            System.out.println(y);  

            for (String prop_x : x.getPropertyKeys()) {
                System.out.println(prop_x +": "+x.getProperty(prop_x));

            }   

        }
        tx1.success();
    }
    finally {
        tx1.close();

    }

试试看{
ExecutionEngine=新的ExecutionEngine（graphDb）；
ExecutionResult=engine.execute（“匹配（发送方：个人）-[：电子邮件]（接收方）返回发送方，计数（接收方）作为计数，按计数描述收集（接收方.个人）作为接收方订单”）；
//ExecutionResult=engine.execute（“匹配（发送者：人）-[：电子邮件]->（接收者）与发送者，收集（接收者.人）作为接收者，返回{发送者：发送者.人，接收者：接收者）按大小排序（接收者）描述”）；
//System.out.println（result.dumpToString（））；
LinkedList_prop=新建LinkedList（）；
用于（地图行：结果）{
Node x=（Node）row.get（“发送方”）；
对象y=行获取（“接收者”）；
系统输出打印项次（y）；
对于（字符串prop_x:x.getPropertyKeys（））{
System.out.println（prop_x+”：“+x.getProperty（prop_x））；
}   
}
tx1.成功（）；
}
最后{
tx1.close（）；
}

---

在匹配查询中，我使用了“collect（receiver.person）as receivers”而不是“collect（receiver）as receivers”。它起作用了。

谢谢你的回答。是的。row.get（“receivers”）只会抛出错误。但是get（“sender”）起作用了！！。我已经编辑了这个问题。