java - NullPointerException，在scala中填充vaadin的IndexedContainer时

Question

我试图用java.util.List[POJO]填充Scala中Vaadin的IndexedContainer强>.

有问题吗？ -> 抛出 NullPointerException。

哪里？ -> 位置显示在带注释的代码片段中。

注意 -> 不同的是，我使用迭代器来填充容器。我有 7 个对象，其中 1 个对象运行正常，但在插入第二个对象时抛出异常。

我正在对其他分层容器执行相同的操作，并且它们工作正常。

要点:列表不包含任何空数据项。输出也在不同的代码片段中给出，但有异常(exception)。

def getOtherAccessContainer(): IndexedContainer = {
    var container = new IndexedContainer
    container.addContainerProperty("User", classOf[Any], "-")
    container.addContainerProperty("user_id", classOf[Any], "-")
    container.addContainerProperty("User Group", classOf[Any], "-")
    container.addContainerProperty("user_familyid", classOf[Any], "-")
    container.addContainerProperty("Object Type", classOf[Any], "-")
    container.addContainerProperty("Object", classOf[Any], "-")
    container.addContainerProperty("object_id", classOf[Any], "-")
    container.addContainerProperty("Object Group", classOf[Any], "-")
    container.addContainerProperty("object_familyid", classOf[Any], "-")
    container.addContainerProperty("Permission", classOf[Any], "-")

    val access_list = accessor.getGrantedObjectList(accessibleuserlist);
    var iterator = access_list.iterator()

    var iterator2 = access_list.iterator()
    println()
    // Just to show that list of POJO is not having null value.
    while (iterator2.hasNext()) {
      val pojo_obj = iterator2.next()
      println(pojo_obj.username + "---" + pojo_obj.user_id + "---" + pojo_obj.user_familyname + "---" + pojo_obj.user_family_id + "---" + pojo_obj.object_type + "---" + pojo_obj.object_name +
        "---" + pojo_obj.object_id + "---" + pojo_obj.object_familyname + "---" + pojo_obj.object_family_id + "---" + pojo_obj.permission)
    }


    // This loop fills the data in container.
    while (iterator.hasNext()) {
      val pojo_obj = iterator.next()
      var child: Item = container.addItem()
      if (pojo_obj == null) {
        println("Trouble is here." + pojo_obj.username)
      }
      // Print some properties of POJO to be inserted before the Insertion is occured.     
      println("pojo_obj properties :-) " + pojo_obj.username + "---" + pojo_obj.object_name + "---" + pojo_obj.user_id + "---" + pojo_obj.user_familyname + "---" + pojo_obj.user_family_id)

      child.getItemProperty("User").asInstanceOf[Property[Any]].setValue(pojo_obj.username) // <- This line Throws the NullPointerException during 2nd Iteration.
      child.getItemProperty("user_id").asInstanceOf[Property[Any]].setValue(pojo_obj.user_id)// <- If I omitted the line above, It throws NullPointerException for this line and so on. 
      child.getItemProperty("User Group").asInstanceOf[Property[Any]].setValue(pojo_obj.user_familyname)
      child.getItemProperty("user_familyid").asInstanceOf[Property[Any]].setValue(pojo_obj.user_family_id)
      child.getItemProperty("Object Type").asInstanceOf[Property[Any]].setValue(pojo_obj.object_type)
      child.getItemProperty("Object").asInstanceOf[Property[Any]].setValue(pojo_obj.object_name)
      child.getItemProperty("object_id").asInstanceOf[Property[Any]].setValue(pojo_obj.object_id)
      child.getItemProperty("Object Group").asInstanceOf[Property[Any]].setValue(pojo_obj.object_familyname)
      child.getItemProperty("object_familyid").asInstanceOf[Property[Any]].setValue(pojo_obj.object_family_id)
      child.getItemProperty("Permission").asInstanceOf[Property[Any]].setValue(pojo_obj.permission.toString())

    }
    container
  }

以下是输出:

parth---4cc19690-e819-11e5-a3a1-c1cf090b354c---Analytics Team---ff81457a-e9cf-11e5-9ce9-5e5517507c66---sa_table---App_Welcome---bce4bd70-ec34-11e5-bbd6-91bbc2299c26---system---9aa06252-e9c6-11e5-9ce9-5e5517507c66---1
ravi---d1515310-e9ad-11e5-b18e-c1cf090b354c---Analytics Team---ff81457a-e9cf-11e5-9ce9-5e5517507c66---sa_table---App_Welcome---bce4bd70-ec34-11e5-bbd6-91bbc2299c26---system---9aa06252-e9c6-11e5-9ce9-5e5517507c66---1
uttam---dca16200-e462-11e5-90ec-c1cf090b354c---Analytics Team---ff81457a-e9cf-11e5-9ce9-5e5517507c66---sa_table---App_Welcome---bce4bd70-ec34-11e5-bbd6-91bbc2299c26---system---9aa06252-e9c6-11e5-9ce9-5e5517507c66---1
parth---4cc19690-e819-11e5-a3a1-c1cf090b354c---parth---4cc19690-e819-11e5-a3a1-c1cf090b354c---sa_table--- cluster_test---19713360-ed94-11e5-bf9e-c1cf090b354c---cluster_test---19713360-ed94-11e5-bf9e-c1cf090b354c---0
parth---4cc19690-e819-11e5-a3a1-c1cf090b354c---Analytics Team---ff81457a-e9cf-11e5-9ce9-5e5517507c66---sa_table---App_Welcome---bce4bd70-ec34-11e5-bbd6-91bbc2299c26---system---9aa06252-e9c6-11e5-9ce9-5e5517507c66---1
uttam---dca16200-e462-11e5-90ec-c1cf090b354c---Analytics Team---ff81457a-e9cf-11e5-9ce9-5e5517507c66---sa_table---App_Welcome---bce4bd70-ec34-11e5-bbd6-91bbc2299c26---system---9aa06252-e9c6-11e5-9ce9-5e5517507c66---1
ravi---d1515310-e9ad-11e5-b18e-c1cf090b354c---Analytics Team---ff81457a-e9cf-11e5-9ce9-5e5517507c66---sa_table---App_Welcome---bce4bd70-ec34-11e5-bbd6-91bbc2299c26---system---9aa06252-e9c6-11e5-9ce9-5e5517507c66---1
pojo_obj properties :-) parth---App_Welcome---4cc19690-e819-11e5-a3a1-c1cf090b354c---Analytics Team---ff81457a-e9cf-11e5-9ce9-5e5517507c66
pojo_obj properties :-) ravi---App_Welcome---d1515310-e9ad-11e5-b18e-c1cf090b354c---Analytics Team---ff81457a-e9cf-11e5-9ce9-5e5517507c66

16/04/04 11:50:42 ERROR DefaultErrorHandler: 
java.lang.NullPointerException
    at com.system.tableManager.TreeStructContainer.getOtherAccessContainer(TreeStructContainer.scala:245)
    at com.analytics.UI.views.ObjectLevelAccess$1.valueChange(ObjectLevelAccess.java:135)
    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:498)
    at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:508)
    at com.vaadin.event.EventRouter.fireEvent(EventRouter.java:198)
    at com.vaadin.event.EventRouter.fireEvent(EventRouter.java:161)
    at com.vaadin.server.AbstractClientConnector.fireEvent(AbstractClientConnector.java:1008)
    at com.vaadin.ui.AbstractField.fireValueChange(AbstractField.java:1159)
    at com.vaadin.ui.AbstractField.setValue(AbstractField.java:570)
    at com.vaadin.ui.AbstractSelect.setValue(AbstractSelect.java:729)
    at com.vaadin.ui.AbstractField.setValue(AbstractField.java:468)
    at com.vaadin.ui.ComboBox.changeVariables(ComboBox.java:730)
    at com.vaadin.server.communication.ServerRpcHandler.changeVariables(ServerRpcHandler.java:603)
    at com.vaadin.server.communication.ServerRpcHandler.handleInvocations(ServerRpcHandler.java:422)
    at com.vaadin.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:273)
    at com.vaadin.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:79)
    at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:41)
    at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1409)
    at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:364)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

Answer 1

有时 Vaadin 容器 addItem 返回 null 而不是新的 Item id。

因此，更好的选择是使用 container.getItem(container.addItem) 而不是 container.addItem()。

或者添加您自己的自定义项目 ID，例如 container.addItem(customId) 来添加您想要在容器中添加的项目。