NullPointerException when trying to reload IndexedContainer with fresh data - vaadin

Question

I'm trying to "reload" an IndexedContainer with new fresh data, but get a NPE.
I have a addItemsToContainer(List<Person> persons) method that I use to populate my container.
Let's say my Person list contains 100 person objects. When I first call addItemsToContainer(List<Person> persons), my container is populated and everything is fine.
However, the second time I call the method, I get a NullPointerException in setValue().
Now, it seems like removeAllItems() do remove all items, but all ItemId's are left in the container. This means that the second time I call the method, the first automatically generated ItemId is 101. Is this the reason I get the NPE? When debugging, I can see that I get the proper value back from person.getId().
My addItemsToContainer method
public void addItemsToContainer(List<Person> persons) {
removeAllItems();
for (Person person : persons) {
Object itemId = addItem();
getContainerProperty(itemId, "Id").setValue(person.getId()); // <-- NPE here
getContainerProperty(itemId, "Name").setValue(person.getName());
}
}
The stacktrace
(ExampleMainTableContainer.java:94 is the statement I marked in the addItemsToContainer method)
com.vaadin.server.ServerRpcManager$RpcInvocationException: Unable to invoke method click in com.vaadin.shared.ui.button.ButtonServerRpc
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:170)
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:118)
at com.vaadin.server.communication.ServerRpcHandler.handleBurst(ServerRpcHandler.java:214)
at com.vaadin.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:111)
at com.vaadin.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:91)
at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:37)
at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1371)
at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:238)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:168)
... 24 more
Caused by: com.vaadin.event.ListenerMethod$MethodException: Invocation of method buttonClick in com.example.myapp.web.view.ExampleView$1 failed.
at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:528)
at com.vaadin.event.EventRouter.fireEvent(EventRouter.java:167)
at com.vaadin.server.AbstractClientConnector.fireEvent(AbstractClientConnector.java:969)
at com.vaadin.ui.Button.fireClick(Button.java:368)
at com.vaadin.ui.Button$1.click(Button.java:57)
... 29 more
Caused by: java.lang.NullPointerException
at com.example.myapp.web.view.ExampleMainTableContainer.addItemsToContainer(ExampleMainTableContainer.java:94)
at com.example.myapp.web.view.ExampleMainTable.addMainTableItems(ExampleMainTable.java:172)
at com.example.myapp.web.view.ExampleMainTable.experiment(ExampleMainTable.java:86)
at com.example.myapp.web.view.ExampleView$1.buttonClick(ExampleView.java:208)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:508)
... 33 more

Answer 1

The method getContainerProperty(...) returned null, leading to the NPE.
This happened because I filtered my container prior to the second call to addItemsToContainer(...).
When I add a new item to my container, it gets added to allItemIds - the filteredItemIds is left empty. Now, when getContainerProperty(...) is called, it does a check if the container was filtered. If it was filtered, it returns filteredItemIds instead of allItemIds. This meant, of course, that this statement returned an empty list of objects, leading to ´getContainerProperty(...)´ returning null - which finally lead to the NPE.
The solution was to simply add removeAllContainerFilters(); before my ´getContainerProperty(...)´ calls.