java.lang.NullPointerException: factory 这个异常有见过的没？

java.lang.NullPointerException: factory
at org.zkoss.jsp.spec.AbstractJspFactory.<init>(AbstractJspFactory.java:46)
at org.zkoss.jsp.spec.v21.JspFactoryImpl.<init>(JspFactoryImpl.java:50)
at org.zkoss.jsp.spec.v21.JspFactoryImpl.<clinit>(JspFactoryImpl.java:58)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at org.zkoss.lang.Classes.forNameByThread(Classes.java:199)
at org.zkoss.jsp.spec.JspFactoryContextListener.initJspFactory(JspFactoryContextListener.java:80)
at org.zkoss.jsp.spec.JspFactoryContextListener.startCorrectVersionJspFactory2(JspFactoryContextListener.java:67)
at org.zkoss.jsp.spec.JspFactoryContextListener.contextInitialized(JspFactoryContextListener.java:48)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3843)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4342)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:926)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:889)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1149)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
at org.apache.catalina.core.StandardService.start(StandardService.java:516)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:578)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)