Et tu, Richard. I stabbed myself in the back with Vaadin and Lombok

The problem I struggled with for days... 

Take a simple Vaadin tab sheet.
Add a sheet , remove a sheet etc. Nothing hard at all right ?

I was getting the below error when the screen was repainted.

SEVERE: Terminal error:
java.lang.NullPointerException
 at com.vaadin.ui.TabSheet.paintContent(TabSheet.java:390)
 at com.vaadin.ui.AbstractComponent.paint(AbstractComponent.java:781)
 at com.vaadin.ui.AbstractSplitPanel.paintContent(AbstractSplitPanel.java:235)
 at com.vaadin.ui.AbstractComponent.paint(AbstractComponent.java:781)
 at com.vaadin.ui.AbstractOrderedLayout.paintContent(AbstractOrderedLayout.java:187)
 at com.vaadin.ui.AbstractComponent.paint(AbstractComponent.java:781)
 at com.vaadin.ui.Panel.paintContent(Panel.java:269)
 at com.vaadin.ui.Window.paintContent(Window.java:641)
 at com.vaadin.ui.AbstractComponent.paint(AbstractComponent.java:781)
 at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.writeUidlResponce(AbstractCommunicationManager.java:1046)
 at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.paintAfterVariableChanges(AbstractCommunicationManager.java:927)
 at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.doHandleUidlRequest(AbstractCommunicationManager.java:794)
 at com.vaadin.terminal.gwt.server.CommunicationManager.handleUidlRequest(CommunicationManager.java:296)
 at com.vaadin.terminal.gwt.server.AbstractApplicationServlet.service(AbstractApplicationServlet.java:501)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
 at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:169)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
 at org.apache.catalina.core.StandardHostValve.__invoke(StandardHostValve.java:168)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
 at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
 at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:964)
 at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
 at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:304)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
 at java.lang.Thread.run(Thread.java:722)

There seems to be a Vaadin ticket for this : http://dev.vaadin.com/ticket/4179  

The culprit

My favorite java Add On : Lombok
Actually I can't blame Lombok or Vaadin, this is my misuse of Lombok inside Vaadin

I decorated my component with @Data
That means the equals and hashCode were generated by all the fields in the class.

com.vaadin.ui.TabSheet.java contains an internal representation of the tabs in a HashMap tabs.

If the hashmap can not find your component because the equals has changed. you will get what I did.

            Tab tab = tabs.get(component);//will return null

            target.startTag("tab");
            if (!tab.isEnabled() && tab.isVisible()) {