Unable to invoke method requestRows in com.vaadin.shared.data.DataRequestRpc
com.vaadin.server.ServerRpcManager$RpcInvocationException: Unable to invoke method requestRows in com.vaadin.shared.data.DataRequestRpc
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:162) ~[vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:119) ~[vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.communication.ServerRpcHandler.handleInvocation(ServerRpcHandler.java:437) [vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.communication.ServerRpcHandler.handleInvocations(ServerRpcHandler.java:402) [vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:273) [vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:90) [vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:41) [vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1422) [vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:380) [vaadin-server-7.7.11.jar:7.7.11]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [servlet-api.jar:?]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) [catalina.jar:8.5.13]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [catalina.jar:8.5.13]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-websocket.jar:8.5.13]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [catalina.jar:8.5.13]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [catalina.jar:8.5.13]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [catalina.jar:8.5.13]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [catalina.jar:8.5.13]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) [catalina.jar:8.5.13]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [catalina.jar:8.5.13]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) [catalina.jar:8.5.13]
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624) [catalina.jar:8.5.13]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [catalina.jar:8.5.13]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:341) [catalina.jar:8.5.13]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) [tomcat-coyote.jar:8.5.13]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-coyote.jar:8.5.13]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861) [tomcat-coyote.jar:8.5.13]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) [tomcat-coyote.jar:8.5.13]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-coyote.jar:8.5.13]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [?:1.8.0_131]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [?:1.8.0_131]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-util.jar:8.5.13]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_131]
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_131]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_131]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_131]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_131]
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:158) ~[vaadin-server-7.7.11.jar:7.7.11]
… 31 more
Caused by: java.lang.NullPointerException
at com.vaadin.ui.Grid$RowDataGenerator.writeData(Grid.java:2317) ~[vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.ui.Grid$RowDataGenerator.generateData(Grid.java:2276) ~[vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.communication.data.RpcDataProviderExtension.getRowData(RpcDataProviderExtension.java:404) ~[vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.communication.data.RpcDataProviderExtension.pushRowData(RpcDataProviderExtension.java:392) ~[vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.communication.data.RpcDataProviderExtension.access$900(RpcDataProviderExtension.java:65) ~[vaadin-server-7.7.11.jar:7.7.11]
at com.vaadin.server.communication.data.RpcDataProviderExtension$2.requestRows(RpcDataProviderExtension.java:293) ~[vaadin-server-7.7.11.jar:7.7.11]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_131]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_131]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_131]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_131]
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:158) ~[vaadin-server-7.7.11.jar:7.7.11]
… 31 more