Minor Description
Did not manifest in the UI, but present as a stacktrace (below).
This SO article http://stackoverflow.com/questions/37048084/is-this-null-pointer-exception-in-treemap-due-to-concurrent-access suggests concurrent exception.
Fix probably to introduce the 'synchronized' keyword at some judicious point.
stacktrace:
00:05:59,617 [RequestCycleExtra ] ******************************** 00:05:59,617 [RequestCycleExtra ] Handling the following exception org.apache.wicket.WicketRuntimeException: Exception in rendering component: [MessageContainer [Component id = _message_5]] at org.apache.wicket.Component.internalRenderComponent(Component.java:2560) at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1496) at org.apache.wicket.Component.internalRender(Component.java:2366) at org.apache.wicket.Component.render(Component.java:2294) at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1392) at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1557) at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1532) at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1487) at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71) at org.apache.wicket.Component.internalRenderComponent(Component.java:2536) at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1496) at org.apache.wicket.Component.internalRender(Component.java:2366) at org.apache.wicket.Component.render(Component.java:2294) at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1392) at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1557) at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1532) at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1487) at org.apache.wicket.markup.html.form.Form.onComponentTagBody(Form.java:1743) at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71) at org.apache.wicket.Component.internalRenderComponent(Component.java:2536) at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1496) at org.apache.wicket.Component.internalRender(Component.java:2366) at org.apache.wicket.Component.render(Component.java:2294) at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1392) at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1557) at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1532) at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689) at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76) at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112) at org.apache.wicket.Component.internalRenderComponent(Component.java:2536) at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1496) at org.apache.wicket.Component.internalRender(Component.java:2366) at org.apache.wicket.Component.render(Component.java:2294) at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1392) at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1557) at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1532) at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1487) at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71) at org.apache.wicket.Component.internalRenderComponent(Component.java:2536) at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1496) at org.apache.wicket.Component.internalRender(Component.java:2366) at org.apache.wicket.Component.render(Component.java:2294) at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1392) at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1557) at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1532) at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1487) at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71) at org.apache.wicket.Component.internalRenderComponent(Component.java:2536) at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1496) at org.apache.wicket.Component.internalRender(Component.java:2366) at org.apache.wicket.Component.render(Component.java:2294) at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1392) at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1557) at org.apache.wicket.Page.onRender(Page.java:887) at org.apache.wicket.markup.html.WebPage.onRender(WebPage.java:143) at org.apache.wicket.Component.internalRender(Component.java:2366) at org.apache.wicket.Component.render(Component.java:2294) at org.apache.wicket.Page.renderPage(Page.java:1024) at org.apache.wicket.request.handler.render.WebPageRenderer.renderPage(WebPageRenderer.java:139) at org.apache.wicket.request.handler.render.WebPageRenderer.respond(WebPageRenderer.java:229) at org.apache.wicket.core.request.handler.RenderPageRequestHandler.respond(RenderPageRequestHandler.java:175) at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:890) at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64) at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261) at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218) at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289) at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259) at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:201) at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:282) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1668) at org.apache.isis.core.webapp.diagnostics.IsisLogOnExceptionFilter.doFilter(IsisLogOnExceptionFilter.java:52) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1668) at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449) at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365) at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90) at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83) at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383) at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362) at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1668) at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:581) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548) at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226) at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1158) at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:511) at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185) at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1090) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:119) at org.eclipse.jetty.server.Server.handle(Server.java:517) at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:308) at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:242) at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:261) at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:95) at org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:75) at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceAndRun(ExecuteProduceConsume.java:213) at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:147) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:654) at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:572) at java.lang.Thread.run(Thread.java:745) Caused by: java.lang.RuntimeException: An error occurred while executing code in a temporary session at org.apache.isis.core.runtime.system.session.IsisSessionFactory.doInSession(IsisSessionFactory.java:349) at org.apache.isis.core.runtime.system.session.IsisSessionFactory.doInSession(IsisSessionFactory.java:327) at org.apache.isis.viewer.wicket.viewer.integration.wicket.LocalizerForIsis.translate(LocalizerForIsis.java:75) at org.apache.isis.viewer.wicket.viewer.integration.wicket.LocalizerForIsis.getString(LocalizerForIsis.java:62) at org.apache.wicket.Localizer.getString(Localizer.java:201) at org.apache.wicket.Localizer.getString(Localizer.java:150) at org.apache.wicket.markup.resolver.WicketMessageResolver$MessageContainer.onComponentTagBody(WicketMessageResolver.java:203) at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71) at org.apache.wicket.Component.internalRenderComponent(Component.java:2536) ... 100 more Caused by: java.lang.NullPointerException at java.util.TreeMap.rotateLeft(TreeMap.java:2224) at java.util.TreeMap.fixAfterInsertion(TreeMap.java:2291) at java.util.TreeMap.put(TreeMap.java:582) at org.apache.isis.core.runtime.services.i18n.po.PoWriter.blockFor(PoWriter.java:143) at org.apache.isis.core.runtime.services.i18n.po.PoWriter.translate(PoWriter.java:120) at org.apache.isis.core.runtime.services.i18n.po.TranslationServicePo.translate(TranslationServicePo.java:103) at org.apache.isis.viewer.wicket.viewer.integration.wicket.LocalizerForIsis.translate(LocalizerForIsis.java:144) at org.apache.isis.viewer.wicket.viewer.integration.wicket.LocalizerForIsis.access$000(LocalizerForIsis.java:45) at org.apache.isis.viewer.wicket.viewer.integration.wicket.LocalizerForIsis$1.call(LocalizerForIsis.java:78) at org.apache.isis.viewer.wicket.viewer.integration.wicket.LocalizerForIsis$1.call(LocalizerForIsis.java:75) at org.apache.isis.core.runtime.system.session.IsisSessionFactory.doInSession(IsisSessionFactory.java:347) ... 108 more
