通過java檢索neo4j節點數據時出錯

Question

我通過talend將大約60k個節點加載到neo4j中。 我想通過java訪問這些節點。 Java代碼只能獲取neo4j本身附帶的單個節點，即第0個節點。

我的Java代碼是：

package com.Neo4J;

import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import javax.naming.spi.DirStateFactory.Result;

import org.neo4j.cypher.javacompat.ExecutionEngine;
import org.neo4j.cypher.javacompat.ExecutionResult;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Transaction;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;
import org.neo4j.helpers.collection.IteratorUtil;
import org.neo4j.kernel.impl.util.FileUtils;
import org.neo4j.tooling.GlobalGraphOperations;

public class CaseNeo4J {

private static final String DB_PATH = "data/graph.db";
GraphDatabaseService graphDataService;
String nodeResult, resultString, columnsString;
String rows = "";

public static void main(String args[]) {
    CaseNeo4J neoobj = new CaseNeo4J();
    neoobj.connect();

}

void connect() {

    graphDataService = new GraphDatabaseFactory().newEmbeddedDatabase(DB_PATH);
    Transaction transaction = graphDataService.beginTx();

    try {
        ExecutionEngine engine = new ExecutionEngine(graphDataService);
        ExecutionResult result = engine.execute("START n = node(0) return     n");
        System.out.println(result.dumpToString());
    }

    finally {
        transaction.finish();
    }
}
}

正如你在CQL中看到的那樣，我試圖退出節點（0），這給了我正確的結果

+-----------+
| n         |
+-----------+
| Node[0]{} |
+-----------+
1 row

但是一旦我給出START n = node（1）這樣的查詢返回n它就會拋出錯誤 -

Exception in thread "main" org.neo4j.cypher.EntityNotFoundException: Node 1 not found
    at      org.neo4j.cypher.internal.spi.gdsimpl.GDSBackedQueryContext$$anon$1.getById(GDSBackedQueryC     ontext.scala:80)
at   org.neo4j.cypher.internal.spi.gdsimpl.GDSBackedQueryContext$$anon$1.getById(GDSBackedQueryC     ontext.scala:48)
at   org.neo4j.cypher.internal.executionplan.builders.NodeByIdBuilder$$anonfun$org$neo4j$cypher$     internal$executionplan$builders$NodeByIdBuilder$$f$1$1.apply(NodeByIdBuilder.scala:41)
at org.neo4j.cypher.internal.executionplan.builders.NodeByIdBuilder$$anonfun$org$neo4j$cypher$     internal$executionplan$builders$NodeByIdBuilder$$f$1$1.apply(NodeByIdBuilder.scala:41)
at org.neo4j.cypher.internal.executionplan.builders.GetGraphElements$.org$neo4j$cypher$interna     l$executionplan$builders$GetGraphElements$$castElement$1(GetGraphElements.scala:30)
at org.neo4j.cypher.internal.executionplan.builders.GetGraphElements$$anonfun$getElements$3.ap     ply(GetGraphElements.scala:40)
at scala.collection.Iterator$$anon$11.next(Iterator.scala:328)
at scala.collection.Iterator$$anon$11.next(Iterator.scala:328)
at scala.collection.Iterator$$anon$13.next(Iterator.scala:372)
at org.neo4j.cypher.internal.ClosingIterator$$anonfun$next$1.apply(ClosingIterator.scala:44)
at org.neo4j.cypher.internal.ClosingIterator.failIfThrows(ClosingIterator.scala:86)
at org.neo4j.cypher.internal.ClosingIterator.next(ClosingIterator.scala:43)
at scala.collection.Iterator$class.foreach(Iterator.scala:727)
at org.neo4j.cypher.internal.ClosingIterator.foreach(ClosingIterator.scala:31)
at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:48)
at scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:178)
at scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:45)
at scala.collection.TraversableOnce$class.to(TraversableOnce.scala:259)
at org.neo4j.cypher.internal.ClosingIterator.to(ClosingIterator.scala:31)
at scala.collection.TraversableOnce$class.toList(TraversableOnce.scala:243)
at org.neo4j.cypher.internal.ClosingIterator.toList(ClosingIterator.scala:31)
at org.neo4j.cypher.PipeExecutionResult.eagerResult(PipeExecutionResult.scala:100)
at org.neo4j.cypher.PipeExecutionResult.dumpToString(PipeExecutionResult.scala:103)
at org.neo4j.cypher.PipeExecutionResult.dumpToString$lzycompute(PipeExecutionResult.scala:143)
at org.neo4j.cypher.PipeExecutionResult.dumpToString(PipeExecutionResult.scala:140)
at org.neo4j.cypher.javacompat.ExecutionResult.dumpToString(ExecutionResult.java:102)
at com.Neo4J.CaseNeo4J.connect(CaseNeo4J.java:45)
at com.Neo4J.CaseNeo4J.main(CaseNeo4J.java:32)

但是如果我運行START n = node（1）在neo4j shell的web UI中返回此查詢，它會給我正確的結果。

對此有什么想法嗎？ 如果我在這里得到一些解決方案，我將非常感激。 謝謝！

Answer 1

您確定要使用與neo4j服務器實例和talend使用的DB_PATH相同的數據位置嗎？ 你能檢查絕對路徑嗎？ AFAIK在沒有數據的路徑上啟動嵌入式數據庫實例時，會從頭開始創建一個空數據集，該數據集只包含一個id為0的根節點。

Answer 2

能夠解決這一挑戰。 提及完整的DB_PATH。 謝謝所有給我時間的人。