Neo4j的暗號查詢使用Java API

Question

我使用下面的查詢

 START n=node(*) 
    MATCH(n) 
    WHERE n.Gender ?="Female" 
    RETURN n 

其完美運行在服務器1.9.6問題。

我的程序如下

void query() 
     { 
     ExecutionResult result,; 
     Transaction tx=null; 
    ExecutionEngine engine = new ExecutionEngine(graphDb); 

    try 
    { 
     String name="Female"; 
     tx=graphDb.beginTx(); 
    result=engine.execute("start n=node(*)match(n)where n.Gender ?={Female} return n"); 
     System.out.println(result.dumpToString()); 
     tx.success(); 
    } 

    catch(Exception e) 
    { 
     try 
     {   
      File f=new File("trace.txt"); 
      BufferedWriter br=new BufferedWriter(new FileWriter(f,true)); 
      tx.failure(); 
      k=Arrays.toString(e.getStackTrace()); 
      System.out.println(k); 
      br.write(k); 
      br.close(); 
      throw new IOException(); 
     } 
     catch (Exception ex) 
     { 
     } 
     } 
    finally 
    { 
     tx.finish(); 
    } 

} 

當我嘗試通過節目進入catch塊，並打印以下的堆棧跟蹤

  [org.neo4j.cypher.internal.pipes.QueryState$$anonfun$getParam$1.apply(QueryState.scala:60), 
      org.neo4j.cypher.internal.pipes.QueryState$$anonfun$getParam$1.apply(QueryState.scala:60), 
      scala.collection.MapLike$class.getOrElse(MapLike.scala:128), 
      scala.collection.AbstractMap.getOrElse(Map.scala:58), 
      org.neo4j.cypher.internal.pipes.QueryState.getParam(QueryState.scala:60), 
      org.neo4j.cypher.internal.commands.expressions.ParameterExpression.apply(ParameterExpression.scala:27), 
      org.neo4j.cypher.internal.commands.Equals.isMatch(ComparablePredicate.scala:59), 
      org.neo4j.cypher.internal.commands.NullablePredicate.isMatch(Predicate.scala:59), 
      org.neo4j.cypher.internal.pipes.FilterPipe$$anonfun$internalCreateResults$1.apply(FilterPipe.scala:30), 
      org.neo4j.cypher.internal.pipes.FilterPipe$$anonfun$internalCreateResults$1.apply(FilterPipe.scala:30), 
      scala.collection.Iterator$$anon$14.hasNext(Iterator.scala:390), 
      org.neo4j.cypher.internal.ClosingIterator$$anonfun$next$1.apply(ClosingIterator.scala:45), 
      org.neo4j.cypher.internal.ClosingIterator.failIfThrows(ClosingIterator.scala:86), 
      org.neo4j.cypher.internal.ClosingIterator.next(ClosingIterator.scala:43), 
      scala.collection.Iterator$class.foreach(Iterator.scala:727), 
      org.neo4j.cypher.internal.ClosingIterator.foreach(ClosingIterator.scala:31), 
      scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:48), 
      scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:178), 
      scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:45), 
      scala.collection.TraversableOnce$class.to(TraversableOnce.scala:259), 
      org.neo4j.cypher.internal.ClosingIterator.to(ClosingIterator.scala:31), 
      scala.collection.TraversableOnce$class.toList(TraversableOnce.scala:243), 
      org.neo4j.cypher.internal.ClosingIterator.toList(ClosingIterator.scala:31), 
      org.neo4j.cypher.PipeExecutionResult.eagerResult(PipeExecutionResult.scala:100), 
      org.neo4j.cypher.PipeExecutionResult.dumpToString(PipeExecutionResult.scala:103), 
      org.neo4j.cypher.PipeExecutionResult.dumpToString$lzycompute(PipeExecutionResult.scala:143), 
      org.neo4j.cypher.PipeExecutionResult.dumpToString(PipeExecutionResult.scala:140), 
      org.neo4j.cypher.javacompat.ExecutionResult.dumpToString(ExecutionResult.java:102), 
      Neo4jQuery.query(Neo4jQuery.java:90), Neo4jQuery.main(Neo4jQuery.java:35), 
      __SHELL3.run(__SHELL3.java:6), sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method), 
      sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57), 
      sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43), 
      java.lang.reflect.Method.invoke(Method.java:606), bluej.runtime.ExecServer$3.run(ExecServer.java:725)] 

我想我傳遞參數「來執行它女性「的方式是錯誤的。

Answer 1

我應該開始說我不熟悉Neo4j的Java API。但是，從我所看到的：

在Cypher支架

MATCH (n) 

不正確。您需要描述完整路徑，如MATCH (n)-->(m)或MATCH (n)-[:friend_of]-(m)，或者一起跳過匹配條款。在你的例子中，你不需要匹配條款，所以你可以跳過它。

第二件事是 - 是你沒有正確地傳遞參數 - 你可以看到如何參數傳遞給ExecutionEgine這裏一些例子：http://docs.neo4j.org/chunked/stable/tutorials-cypher-parameters-java.html

在您的例子，你可以這樣做：

void query() { 
    ExecutionResult result,; 
    Transaction tx=null; 
    ExecutionEngine engine = new ExecutionEngine(graphDb); 

    try 
    { 
     Map<String, Object> params = new HashMap<String, Object>(); 
     params.put("gender", "Female"); 
     tx=graphDb.beginTx(); 
     result = engine.execute("start n=node(*) where n.Gender ?= {gender} return n",params); 
     System.out.println(result.dumpToString()); 
     tx.success(); 
    } 
    catch(Exception e) 
    { 
     try 
     {   
      File f=new File("trace.txt"); 
      BufferedWriter br=new BufferedWriter(new FileWriter(f,true)); 
      tx.failure(); 
      k=Arrays.toString(e.getStackTrace()); 
      System.out.println(k); 
      br.write(k); 
      br.close(); 
      throw new IOException(); 
     } 
     catch (Exception ex) 
     { 
     } 
     } 
    finally 
    { 
     tx.finish(); 
    } 

}