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我想使用 Embedded Neo4j Java API 为关系添加权重。

例如：非常A了解所以他们的关系应该被加权。另一方面，知道的很少，所以他们的关系应该被加权。B5AC1

我怎样才能做到这一点？

PS：我已经尝试过这里的示例：http: //neo4j.com/docs/stable/tutorials-java-embedded-graph-algo.html但它不识别函数createNode( "name", "A", "x", 0d, "y", 0d )和createRelationship( nodeA, nodeC, "length", 2d )。

这是代码：

package com.neo4j.test.test1;

import org.neo4j.graphalgo.CommonEvaluators;
import org.neo4j.graphalgo.EstimateEvaluator;
import org.neo4j.graphalgo.GraphAlgoFactory;
import org.neo4j.graphalgo.PathFinder;
import org.neo4j.graphalgo.WeightedPath;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.PathExpanders;
import org.neo4j.graphdb.Relationship;
import org.neo4j.graphdb.Transaction;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;

import com.neo4j.test.labels.NodeLabels;
import com.neo4j.test.labels.TypeRelation;

public class Test1 {

    public static void main(String[] args) {

        GraphDatabaseFactory dbFactory = new GraphDatabaseFactory();
        GraphDatabaseService db = dbFactory.newEmbeddedDatabase("C:\\Zakaria\\NeoTests\\Test2");

        try (Transaction tx = db.beginTx()) {

            Node nodeA = createNode( "name", "A", "x", 0d, "y", 0d );
            Node nodeB = createNode( "name", "B", "x", 7d, "y", 0d );
            Node nodeC = createNode( "name", "C", "x", 2d, "y", 1d );
            Relationship relAB = createRelationship( nodeA, nodeC, "length", 2d );
            Relationship relBC = createRelationship( nodeC, nodeB, "length", 3d );
            Relationship relAC = createRelationship( nodeA, nodeB, "length", 10d );

            EstimateEvaluator<Double> estimateEvaluator = new EstimateEvaluator<Double>()
            {
                @Override
                public Double getCost( final Node node, final Node goal )
                {
                    double dx = (Double) node.getProperty( "x" ) - (Double) goal.getProperty( "x" );
                    double dy = (Double) node.getProperty( "y" ) - (Double) goal.getProperty( "y" );
                    double result = Math.sqrt( Math.pow( dx, 2 ) + Math.pow( dy, 2 ) );
                    return result;
                }
            };
            PathFinder<WeightedPath> astar = GraphAlgoFactory.aStar(
                    PathExpanders.allTypesAndDirections(),
                    CommonEvaluators.doubleCostEvaluator( "length" ), estimateEvaluator );
            WeightedPath path = astar.findSinglePath( nodeA, nodeB );

            tx.success();

        }

        System.out.println("Done!");

    }

}

它应该给出这个结果：

在此处输入图像描述

它说未定义以下这些功能：

Node nodeA = createNode( "name", "A", "x", 0d, "y", 0d );
Node nodeB = createNode( "name", "B", "x", 7d, "y", 0d );
Node nodeC = createNode( "name", "C", "x", 2d, "y", 1d );
Relationship relAB = createRelationship( nodeA, nodeC, "length", 2d );
Relationship relBC = createRelationship( nodeC, nodeB, "length", 3d );
Relationship relAC = createRelationship( nodeA, nodeB, "length", 10d );

谢谢！

4

3 回答 3

1

正如 Ryan 所说，Java 编译器不会检测到您使用的createNode()方法createRelationship()。

这是一种创建节点的方法，对我有用：

try (Transaction Tx = gdbs.beginTx(){
    Node nodo = gdbs.createNode();
    nodo.addLabel(p);   // if you have Labels
    nodo.setProperty("property1", someValue);
    Tx.success();
    Tx.close();
} catch (Exception e){//do something}

对于关系，仅向您展示如何添加属性：

relationship = firstNode.createRelationshipTo(secondNode, RelTypes.KNOWS );
relationship.setProperty( "message", "brave Neo4j " );

根据您的 Neo4j 版本，您应该了解如何创建节点和关系。最后，我让您创建节点和关系，无需提交它们，您就可以创建路径查找器。我建议您在查询图表之前保留节点作为良好做法。

于 2015-03-27T23:08:33.970 回答
0

这些方法没有定义为 class 中的方法Test1，而是定义为 on GraphDatabaseService。所以，你需要做db.createNode()和db.createRelationship()。那应该对你有用。

于 2015-02-24T16:56:37.360 回答
0

方法 createNode() 和 createRelationship() 未在 neo4j java API 中定义，因为您正在使用它们。

于 2017-05-18T21:29:33.933 回答