Question

我有一个简单的关系测试，我试图使用Rest API（java-rest-binding）https://github.com/neo4j/java-rest-binding来创建一个独特的节点但不幸的是我被困在某事上，这里是详细信息:(非独特的节点和关系工作得非常好，它没有这个，很可能是我做了一些天真的事（请原谅我对neo4j的了解不足）。

final UserModel userModel = new UserModel();
        final HashMap<String, Object> uModelAttributes = new HashMap<String, Object>(0);
        uModelAttributes.put("name", "AnirudhVyas");
        userModel.setAttributes(uModelAttributes);
        final HashSet<Action> buyHistory = new HashSet<Action>();
        final Action buyAction = new Action();
        final ProductModel productModel = new ProductModel();
        final HashMap<String, Object> attributes = new HashMap<String, Object>(0);
        attributes.put("name", "mercedes benz ");
        attributes.put("make", "mercedes benz");
        attributes.put("model", "sls 550");
        attributes.put("year", "2014");
        productModel.setAttributes(attributes);
        buyAction.setProduct(productModel);
        buyHistory.add(buyAction);
        userModel.setBuyHistory(buyHistory);
        System.out.println("Before");
        new UserModelDAO().createCompleteTree(userModel);
        System.out.println("Completed >>>

如果我在dao上使用它：

final RestNode root = api.getOrCreateNode(api.index().forNodes("users", MapUtil.stringMap(IndexManager.PROVIDER, "lucene", "type", "fulltext")), "name", m
                    .getAttributes().get("name"), m.getAttributes());

api.getOrCreateNode(api.index().forNodes("products", MapUtil.stringMap(IndexManager.PROVIDER, "lucene", "type", "fulltext")), "name", buyAction.getProduct().getAttributes().get("name"), buyAction.getProduct().getAttributes()), RelationshipTypes.BOUGHT);

这基本上失败了：

   java.lang.RuntimeException: Error retrieving or creating node for key name and value AnirudhVyas with index users
        at org.neo4j.rest.graphdb.ExecutingRestAPI.getOrCreateNode(ExecutingRestAPI.java:448)
        at org.neo4j.rest.graphdb.RestAPIFacade.getOrCreateNode(RestAPIFacade.java:223)
        at xxxx.xxxx.xxxx.graph.UserModelCreateTasteKeyNeo4JBatchCallback.recordBatch(UserModelCreateTasteKeyNeo4JBatchCallback.java:61)

Answer 1

我通过不使用批处理休息回调解决了这个问题 - 当我简单地使用 - getOrCreateXXX（）for RestAPI时，它就像一个魅力 - 需要进一步调查为什么在BatchCallback上的getOrCreate＃recordBatch（）将表现不同。

Answer 2

有几种方法可以做到，其中一种方法是使用Cypher：

MATCH a
WHERE a.name! = 'nameTofound'
CREATE UNIQUE a-[:Relationship]-c:LABEL
RETURN c

在queryEngine中使用它。它就像一个魅力，请查看以下链接了解更多详情： http://docs.neo4j.org/chunked/milestone/query-create-unique.html

Java代码在这里：

protected static RestNode createOrGetExistingNode(String key, String valueFor, String Rel, String label){
    RestNode node = null;
    final QueryResult<Map<String, Object>> result = GraphRestService.queryEngine.query(String.format("MATCH node WHERE node.%s! ='%s' " +
            "CREATE UNIQUE node-[:%s]-c:%s RETURN c" , key, valueFor, Rel, label), MapUtil.map("reference", 0));
    for (Map<String, Object> column : result) {
        node = (RestNode) column.get("c");
    }
    return node;
}

java-rest-api neo4j的getOrCreate失败

2 个答案: