Java中的ArangoDB AQL查询异常

【问题标题】：ArangoDB AQL Query Exception in JavaJava中的ArangoDB AQL查询异常
【发布时间】：2016-07-22 21:01:39
【问题描述】：

我在java中为ArangoDB执行AQL查询以获得特定节点的后代总数。这是此的代码。

        String nodeUserid = nodeuserid.getText().trim();
        Map<String, Object> bindVars = new MapBuilder().put("nodeid", nodeUserid).get();
        CursorResult cs = arangoDriver.executeAqlQuery("LET x = (FOR v IN 1..1000 OUTBOUND @nodeid GRAPH 'TempPeoplesApp' "
                + " RETURN v.x)"
                + " RETURN SUM(x)", bindVars, null,null);

        int count = cs.getCount();

但在运行时它会给出如下所述的异常，

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1768)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1651)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:204)
    at javafx.scene.Node.fireEvent(Node.java:8175)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:204)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3746)
    at javafx.scene.Scene$MouseHandler.access$1800(Scene.java:3471)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1695)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2486)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:314)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:243)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:345)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:526)
    at com.sun.glass.ui.View.notifyMouse(View.java:898)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
    at com.sun.glass.ui.win.WinApplication$4$1.run(WinApplication.java:112)
    at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1765)
    ... 47 more
Caused by: java.lang.NullPointerException
    at java.lang.Class.isAssignableFrom(Native Method)
    at com.arangodb.entity.EntityDeserializers$CursorEntityDeserializer.getResultObjects(EntityDeserializers.java:686)
    at com.arangodb.entity.EntityDeserializers$CursorEntityDeserializer.deserialize(EntityDeserializers.java:647)
    at com.arangodb.entity.EntityDeserializers$CursorEntityDeserializer.deserialize(EntityDeserializers.java:621)
    at com.google.gson.TreeTypeAdapter.read(TreeTypeAdapter.java:58)
    at com.google.gson.Gson.fromJson(Gson.java:861)
    at com.google.gson.Gson.fromJson(Gson.java:826)
    at com.google.gson.Gson.fromJson(Gson.java:775)
    at com.arangodb.entity.EntityFactory.createEntity(EntityFactory.java:163)
    at com.arangodb.BaseArangoDriver.createEntityImpl(BaseArangoDriver.java:367)
    at com.arangodb.BaseArangoDriver.createEntityWithFallback(BaseArangoDriver.java:259)
    at com.arangodb.BaseArangoDriver.createEntity(BaseArangoDriver.java:236)
    at com.arangodb.BaseArangoDriver.createEntity(BaseArangoDriver.java:311)
    at com.arangodb.impl.InternalCursorDriverImpl.executeCursorEntityQuery(InternalCursorDriverImpl.java:81)
    at com.arangodb.impl.InternalCursorDriverImpl.executeAqlQuery(InternalCursorDriverImpl.java:148)
    at com.arangodb.ArangoDriver.executeAqlQuery(ArangoDriver.java:2144)
    at peoplesapptree.TreeCreationController.displayDescendents(TreeCreationController.java:169)
    ... 57 more

在执行 arangoDriver.executeAqlQuery 方法时出现异常。那么这个查询有什么问题呢？任何人都可以建议吗？我是 ArangoDB 的新手

谢谢， 马扬克

【问题讨论】：

    标签： arangodb


    【解决方案1】：

    您使用哪个版本的 ArangoDB 和 ArangoDB-Java-Driver？

    executeAqlQuery 方法需要知道你期望的 CursorResult 中的哪种类型。这是最后一个参数。在您的情况下，您可能需要一个整数作为 Aql 中的总和。

            String nodeUserid = nodeuserid.getText().trim();
        Map<String, Object> bindVars = new MapBuilder().put("nodeid", nodeUserid).get();
        CursorResult<Integer> cs = arangoDriver.executeAqlQuery(
            "LET x = (FOR v IN 1..1000 OUTBOUND @nodeid GRAPH 'TempPeoplesApp' " + " RETURN v.x)" + " RETURN SUM(x)",
            bindVars, null, Integer.class);

        Integer sum = cs.getUniqueResult();

    getCount() vs getFullCount() vs getUniqueResult()

    getCount() 返回结果总数。 getFullCount() 返回带有 (aql)limit 子句的结果总数。在您的情况下，您的 aql 仅返回 1 个结果，即总和。 aql 可以返回结果列表。当您只有 1 个结果时，您可以使用 getUniqueResult 获得它，当您有 n 个结果时，使用方法 iterator() 或 asList() 并对其进行迭代。

    executeAqlQuery 方法支持所有原始类型、Map、List 和 uniqe aql 结果 Java-Beans 的包装类。

    【讨论】：

    • 您好mpv，感谢您指出正确的方向。我使用的是 ArangoDB 3.0.2 版和 java 驱动程序 2.4 版。现在我用最新的 3.0.0 版本替换了 java 驱动程序。并且不得不像这样更改代码，CursorResult cs = arangoDriver.executeAqlQuery("LET x = (FOR v IN 1..1000 OUTBOUND @nodeid GRAPH 'TempPeoplesApp'" + " RETURN v.x)" + " RETURN SUM(x)",绑定变量，空，空）；在执行此代码时，我在同一行得到 NullPointerException。能给点提示吗？
    • 你能更新你问题中的堆栈输出吗？
    • 谢谢它的工作。 CursorResult 的 getCount()、getFullCount() 和 getUniqueResult() 方法有什么区别，顺便说一下，它是否支持在 executeAqlQuery() 方法中作为参数的所有 java 包装类。
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