java连接neo4j之内嵌式

neo4j连接java目前主要有嵌入式、jdbc和rest api。

嵌入式：使用到的lib包在neo4j下载包的lib里（对于windows，不建议下载exe版，因为不包含代码需要的lib包）

创建节点和关系：

final String DB_PATH = "E:/neo4jdb"; //数据库路径
GraphDatabaseService graphDb = new GraphDatabaseFactory().newEmbeddedDatabase(DB_PATH );  //连接一次比较耗时
Transaction tx = graphDb.beginTx();  //事务
tx.success();
Node firstNode,secondNode;
Relationship relationship;
firstNode = graphDb.createNode();  //创建一个节点
firstNode.setProperty( "name", "node1" );//指明节点的属性
secondNode = graphDb.createNode();
secondNode.setProperty( "name", "node2" );
relationship = firstNode.createRelationshipTo( secondNode, RelTypes.KNOWS );  //创建两个节点间的关系
relationship.setProperty( "weight", 10 ); //设置关系的属性

在创建节点（关系）时如果需要指定类型，则需要声明一个枚举：

private static enum RelTypes implements RelationshipType  //节点的类型和关系的类型
    {
        KNOWS
    }

使用cypher查询数据

ExecutionEngine engine = new ExecutionEngine(this.graphDb);
ExecutionResult result = engine.execute("match n return n.name as name;");
ResourceIterator<String> iterator = result.columnAs("name");  //获取某列值,如果不用as XXX,取值的时候要用n.name
        while(iterator.hasNext()) {
            System.out.println(iterator.next());
        }

查询两点直接的最短路径：目前内嵌式提供多种算法计算最短路径，不过目前只看了shorestPath和dijkstra这两种算法，shorestPath计算两个节点间经过的节点数最小的路径（不考虑节点之间的权重），dijkstra计算两个节点之间权重最小的路径。

//节点之间的最短路径,计算两点之间的经过节点数最小的路径，无关关系的权重
        PathFinder<Path> finder = GraphAlgoFactory.shortestPath(Traversal.expanderForTypes(RelTypes.KNOWS, Direction.OUTGOING), 5);
        Node startNode = this.graphDb.getNodeById(14);
        Node endNode = this.graphDb.getNodeById(17);
        //将经过的节点数相同的路径全部查询回来
        Iterable<Path> paths = finder.findAllPaths(startNode, endNode);
        Iterator<Path> iterator = paths.iterator();
        Path p;
        while(iterator.hasNext()) {
            p = iterator.next();
            System.out.println("shortestPath" + p.toString());
            System.out.println(p.startNode().getId() + "\t" + p.endNode().getId());
        }

        //取所有路径中的第一条
        p = finder.findSinglePath(startNode, endNode);
        System.out.println("shorestPath singlePath :" + p.toString());

        PathFinder<WeightedPath> finder1 = GraphAlgoFactory.dijkstra(
                Traversal.expanderForTypes( RelTypes.KNOWS, Direction.BOTH ), "weight" );

        WeightedPath path = finder1.findSinglePath(startNode, endNode);

        // Get the weight for the found path
        System.out.println(path.weight());
        System.out.println(path.toString());