Neo4j＆Java - 如何總結屬性的所有值？

我創建了一個圖形數據庫。有些節點叫做Vertex，它們的屬性有：attr1:<float-value>,attr2:<float-value>等，以及關係，這些屬性被稱爲Padre，並且具有以下屬性attr1:<float-value>,attr2:<float-value>等。現在，我正在編寫一個Java程序，給定兩個Vertex es（兩個匹配節點ID的整數），檢查它們之間是否存在路徑。如果是，則計算路徑的屬性總和。Neo4j＆Java - 如何總結屬性的所有值？

我已經試過與此代碼：

public void res(Session session, int x, int y) { 

    float z = 0F; 
    boolean found = false; 

    while (!found) { 
     if (x == y) { 
      StatementResult res = session.run("MATCH (N:Vertex) WHERE N.ID=" + x +" RETURN PROPERTIES(N)"); 
      Record record = res.next(); 

      for (String a: record.get("PROPERTIES(N)").keys()) { 
       if(a.equals("ID") || a.equals("IdAlbero")) { 
        continue; 
       } 

       Value k = record.get("PROPERTIES(N)").get(a); 
       z += k.asFloat(); 
      } 

      found = true; 
     } else { 
      StatementResult res = session.run("MATCH (N:Vertex) WHERE N.ID=" + x +" RETURN PROPERTIES(N)"); 
      Record record = res.next(); 
      for (String a: record.get("PROPERTIES(N)").keys()) { 
       if(a.equals("ID") || a.equals("IdAlbero")) { 
        continue; 
       } 

       Value k = record.get("PROPERTIES(N)").get(a); 
       z += k.asFloat(); 
      } 

      res = session.run("MATCH (N:Vertex),(M:Vertex), (N) - [R:Padre] ->(M) WHERE N.ID = " + x + " RETURN PROPERTIES(R)"); 
      record = res.next(); 

      for (String a: record.get("PROPERTIES(R)").keys()) { 
       if (a.equals("ID") || a.equals("IdAlbero")) { 
        continue; 
       } 

       Value k = record.get("PROPERTIES(R)").get(a); 
       z += k.asFloat(); 
      } 
     } 
    } 

    System.out.println(z); 
}

現在，我有一個錯誤給z += k.asFloat()聲明。這是錯誤：

Exception in thread "main" org.neo4j.driver.v1.exceptions.value.Uncoercible: Cannot coerce FLOAT to Java String at org.neo4j.driver.internal.value.ValueAdapter.asString(ValueAdapter.java:84) at Neo4j.res(Neo4j.java:160) at Connessione.connettiti(Connessione.java:27) at Connessione.main(Connessione.java:35).

我該怎麼辦？

來源

2016-12-09 Alcadeias

確定的屬性被存儲爲花車？看起來至少有一個你試圖轉換爲浮點的屬性存儲爲一個字符串。您可以使用Eclipse/NetBeans/IntelliJ調試器來停止執行異常，並查看它的值。或者，您可以只打印該屬性的名稱（'a'）並查看哪個屬性導致該異常。 –

我不知道太多的Java，但你可以使用filter和reduce在一個暗號查詢適合一切：

MATCH (N1:Vertex {id: 1}) 
OPTIONAL MATCH (N1)-[R:Padre]->(N2:Vertex {id:3}) 
WITH N1, FILTER(k in keys(N1) WHERE k<>'id' AND k<>'idAlbero') as kN1, 
    N2, FILTER(k in keys(N2) WHERE k<>'id' AND k<>'idAlbero') as kN2 
WITH N1, kN1, REDUCE(sum1=0.0, k in kN1 | sum1 + toFloat(N1[k])) as sum1, 
    N2, kN2, REDUCE(sum2=0.0, k in kN2 | sum2 + toFloat(N2[k])) as sum2 
WITH N1, kN1, CASE WHEN sum1 IS NULL THEN 0 ELSE sum1 END as sum1, 
    N2, kN2, CASE WHEN sum2 IS NULL THEN 0 ELSE sum2 END as sum2, 
    sum1 + toFloat(sum2) as total 
RETURN N1, kN1, sum1, 
     N2, kN2, sum2, 
     sum1 + sum2 as total

來源

2016-12-10 14:11:13

Neo4j＆Java - 如何總結屬性的所有值？

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