Making Grid with Designer + Data from Database

First I created the Grid Design in pure Java and now I’m trying to work with the Vaadin Designer 2.
Can you help me?

Error Code:

java.lang.NullPointerException: null
at at.nisteria.nisteria.MandantUI.updateGrid(MandantUI.java:55) ~[classes/:na]

at at.nisteria.nisteria.MandantUI.init(MandantUI.java:32) ~[classes/:na]

at com.vaadin.ui.UI.doInit(UI.java:733) ~[vaadin-server-8.0.6.jar:8.0.6]

at com.vaadin.ui.UI$$FastClassBySpringCGLIB$$55080b80.invoke() ~[vaadin-server-8.0.6.jar:8.0.6]

at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738) ~[spring-aop-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136) ~[spring-tx-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673) ~[spring-aop-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at at.nisteria.nisteria.MandantUI$$EnhancerBySpringCGLIB$$8e5a4cd1.doInit() ~[classes/:na]

at com.vaadin.server.communication.UIInitHandler.getBrowserDetailsUI(UIInitHandler.java:216) [vaadin-server-8.0.6.jar:8.0.6]

at com.vaadin.server.communication.UIInitHandler.synchronizedHandleRequest(UIInitHandler.java:74) [vaadin-server-8.0.6.jar:8.0.6]

at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:41) [vaadin-server-8.0.6.jar:8.0.6]

at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1464) [vaadin-server-8.0.6.jar:8.0.6]

at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:381) [vaadin-server-8.0.6.jar:8.0.6]

at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:728) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:467) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:351) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:311) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.springframework.web.servlet.mvc.ServletForwardingController.handleRequestInternal(ServletForwardingController.java:133) [spring-webmvc-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:174) [spring-webmvc-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:50) [spring-webmvc-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967) [spring-webmvc-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) [spring-webmvc-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) [spring-webmvc-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872) [spring-webmvc-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) [spring-web-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) [spring-web-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) [spring-web-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.9.RELEASE.jar:4.3.9.RELEASE]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) [tomcat-embed-core-8.5.15.jar:8.5.15]

at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.15.jar:8.5.15]

at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_131]

at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_131]

at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.15.jar:8.5.15]

at java.lang.Thread.run(Unknown Source) [na:1.8.0_131]

Dateien:
pom.xml → https://pastebin.com/3F7DNvxw
MandantList.html (mit Vaadin Designer 2) → https://pastebin.com/wPiW3XZj
MandantList.java → https://pastebin.com/tkfT9K17
Mandant.java → https://pastebin.com/vv13JZ7J
MandantUI.java → https://pastebin.com/WQnStK9R
NisteraApplication.java → https://pastebin.com/eHni6Y88
MandantService.java → https://pastebin.com/ZxA9E15p