圖數據庫_Neo4j簡單的JavaAPI案例

 入門Neo4j，在官網案例的基礎上添加了兩個方法，下文程序的功能分別是：獲取圖數據庫連接驅動、往標籤添加節點、打印節點信息、獲取所有節點數據、獲取節點和關係、關閉連接。
 執行以下程序需要的lib，分別是Neo4j安裝包下的lib，以及neo4j-java-driver-x.x.x.jar

import org.neo4j.driver.v1.*;
import org.neo4j.driver.v1.types.Node;
import org.neo4j.driver.v1.types.Path;
import org.neo4j.driver.v1.types.Relationship;

import java.util.Iterator;
import java.util.List;

import static org.neo4j.driver.v1.Values.parameters;

public class SmallExample {

    // Driver objects are thread-safe and are typically made available application-wide.
    Driver driver;

    public SmallExample(String uri, String user, String password)
    {
        // 圖數據庫驅動
        driver = GraphDatabase.driver(uri, AuthTokens.basic(user, password));
    }

    /**
     * 添加節點
     * @param name
     */
    private void addPerson(String name)
    {
        // Sessions are lightweight and disposable connection wrappers.
        try (Session session = driver.session())
        {
            // Wrapping Cypher in an explicit transaction provides atomicity
            // and makes handling errors much easier.
            // 寫庫操作需要事務
            try (Transaction tx = session.beginTransaction())
            {
                // x 表示一個佔位符
                tx.run("Merge (a:People {name: {x}})", parameters("x", name));
                tx.success();  // Mark this write as successful.
            }
        }
    }

    /**
     * 打印節點信息
     * @param initial
     */
    private void printPeople(String initial)
    {
        Session session = driver.session();

        // Auto-commit transactions are a quick and easy way to wrap a read.
        // 查詢name 屬性以initial 參數開頭的節點數據
        StatementResult result = session.run(
                "MATCH (a:People) WHERE a.name STARTS WITH {x} RETURN a.name as PeopleName  ",
                parameters("x", initial));
        // Each Cypher execution returns a stream of records.
        while (result.hasNext())
        {
            // Record 是一行記錄，內容是什麼取決於你return 的東西
            Record record = result.next();
            System.out.println("record = " + record);
            // Values can be extracted from a record by index or name.
            // get 的是一個別名，上面的cyther 沒有as 別名話，查詢不出來
            System.out.println(record.get("PeopleName").asString());
        }

    }

    /**
     * 獲取label 中的所有節點數據
     */
    private void getPeoples()
    {
        Session session = driver.session();

        // Auto-commit transactions are a quick and easy way to wrap a read.
        StatementResult result = session.run("MATCH (b:People) RETURN b");
        // Each Cypher execution returns a stream of records.
        while (result.hasNext())
        {
            Record record = result.next();
            System.out.println("record = " + record);   // Record<{b: node<250>}>，key 是b，value 是node<250>，250 代表內置id

            List<Value> list = record.values();
            for(Value v : list)
            {
                Node n = v.asNode();    // 已知value 是一個node（如，node<250>），故將其轉爲Node
                // n.labels() 是一個Iterable
                // n.labels().iterator().next() 獲取的是label，也就是表名的意思
                System.out.println(n.labels().iterator().next() + "--" + n.id());

                // 獲取節點的屬性
                for(String k : n.keys())
                {
                    System.out.println(k + "---" + n.get(k));   // 獲取屬性名和屬性值
                }
                System.out.println("==========================");

            }
        }

    }

    /**
     * 獲取節點和關係
     * 往庫裏添加關係：match (a:People),(b:People) where a.name='Ada' and b.name='Bob' merge (a)-[:Friend]-(b) return a,b
     */
    private void getPeoplesAndRelation()
    {
        Session session = driver.session();

        // Auto-commit transactions are a quick and easy way to wrap a read.
        StatementResult result = session.run(
                "MATCH p=(b:People)-[]-(c) RETURN p");  // return p，p 代表關係，返回的結果是一個path
//                "MATCH (b:People)-[]-(c) RETURN b,c");   // 如果用這句查詢，返回的則是node，可以使用上面getPeople 進行遍歷打印

        while (result.hasNext())
        {
            // Record 是一行記錄，內容是什麼取決於你return的東西；同樣，record.values() 也取決於查詢的是什麼類型
            Record record = result.next();
            System.out.println("record: " + record);

            List<Value> list = record.values();
            for(Value v : list)
            {
                Path p = v.asPath();    // 把獲取的每個value 轉爲path
                Node start = p.start();

                for(String k : start.keys())
                {
                    System.out.println("Start Node's property keys: " + k + "---" + start.get(k) );
                }

                Iterator i = p.relationships().iterator();
                while(i.hasNext())
                {
                    Relationship r = (Relationship)i.next() ;
                    System.out.println("Relation Type: " + r.type());
                    System.out.println("Print id; start node to end node: " + r.startNodeId() + "->"+r.endNodeId());
                    System.out.println("Relation Id: " + r.id());
                }

                Node end = p.end();
                for(String k : end.keys())
                {
                    System.out.println("End Node's property keys: " + k + "---" + end.get(k) );
                }
                System.out.println("==========================");

            }
        }

    }

    public void close()
    {
        // Closing a driver immediately shuts down all open connections.
        driver.close();
    }

    public static void main(String... args)
    {
        SmallExample example = new SmallExample("bolt://oda.com:7687", "neo4j", "123456");
//        example.addPerson("Ada");
//        example.addPerson("Alice");
//        example.addPerson("Bob");
//        example.printPeople("A");
//        example.getPeoples();
        example.getPeoplesAndRelation();
        example.close();
    }

}