我正在运行客户端服务器Web应用程序，并且在加载页面后尝试导航到选项卡。单击历史记录选项卡时，浏览器显示“内部错误”。服务器日志显示由NoClassDefError ....
引起的空指针异常当我从家连接VPN时（连接到服务器的连接速度慢），问题只能重现，而当我从Lan连接时（连接到服务器的连接速度更快），它不会发生
异常跟踪如下所示。有人可以帮助调试此问题吗？源代码没有提供太多细节，这个问题似乎与网络有关吗？
跟踪：
2015-05-08 13:27:28,452 ERROR [qtp1582565014-105] [l.ngna.platform.wicket.AbstractApplication] unexpected error
org.apache.wicket.WicketRuntimeException: Method onLinkClicked of interface org.apache.wicket.markup.html.link.ILinkListener targeted at [IndicatingAjaxFallbackLink [Component id = link]] on component [IndicatingAjaxFallbackLink [Component id = link]] threw an exception
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:268)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:216)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:240)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:226)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:861)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)
at l.ngna.platform.wicket.NaWicketFilter.processRequestCycle(NaWicketFilter.java:41)
at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:201)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:282)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:230)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at l.ngna.platform.usermgmt.security.NaSpnegoAuthenticationFilter.doFilter(NaSpnegoAuthenticationFilter.java:51)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at l.ni.preauthentication.NiPreAuthenticationFilter.doFilter(NiPreAuthenticationFilter.java:45)
at l.ngna.platform.usermgmt.NaPreAuthenticationFilter.doFilter(NaPreAuthenticationFilter.java:33)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:85)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at org.springframework.web.multipart.support.MultipartFilter.doFilterInternal(MultipartFilter.java:119)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:450)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:138)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:564)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:213)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1083)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:379)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:175)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1017)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:136)
at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:109)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
at org.eclipse.jetty.server.Server.handle(Server.java:445)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:260)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:225)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.run(AbstractConnection.java:358)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:596)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:527)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:258)
... 51 more
Caused by: java.lang.NoClassDefFoundError: Could not initialize class l.ngna.optical.gui.network.tree.contour.ContourChartPanel
at l.ngna.optical.gui.network.tree.contour.ContourPanel.<init>(ContourPanel.java:61)
at l.ngna.optical.gui.network.page.PassiveOpticalNetworkViewPage$4.getPanel(PassiveOpticalNetworkViewPage.java:352)
at l.ngna.optical.gui.network.page.PassiveOpticalNetworkViewPage$4.getPanel(PassiveOpticalNetworkViewPage.java:350)
at org.apache.wicket.extensions.markup.html.tabs.TabbedPanel.setCurrentTab(TabbedPanel.java:414)
at org.apache.wicket.extensions.markup.html.tabs.TabbedPanel.setSelectedTab(TabbedPanel.java:389)
at l.ngna.platform.wicket.ajax.IndicatingAjaxTabbedPanel$1.onClick(IndicatingAjaxTabbedPanel.java:27)
at org.apache.wicket.ajax.markup.html.AjaxFallbackLink.onClick(AjaxFallbackLink.java:148)
at org.apache.wicket.markup.html.link.Link.onLinkClicked(Link.java:190)
... 56 more