我将 PrimeFaces 库从 3.2 升级到 3.4.1，但出现此错误：
INFO: Reading config /WEB-INF/faces-config.xml
29.10.2012. 13:03:57 org.apache.catalina.core.StandardContext listenerStart
SEVERE: Exception sending context initialized event to listener instance of class org.apache.myfaces.webapp.StartupServletContextListener
java.lang.NoClassDefFoundError: org/primefaces/model/TreeNode
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2291)
at java.lang.Class.getDeclaredFields(Class.java:1743)
at org.apache.myfaces.config.annotation.AnnotationConfigurator.fields(AnnotationConfigurator.java:520)
at org.apache.myfaces.config.annotation.AnnotationConfigurator.handleManagedBean(AnnotationConfigurator.java:367)
at org.apache.myfaces.config.annotation.AnnotationConfigurator.createFacesConfig(AnnotationConfigurator.java:244)
at org.apache.myfaces.config.annotation.AnnotationConfigurator.createFacesConfig(AnnotationConfigurator.java:91)
at org.apache.myfaces.config.DefaultFacesConfigurationProvider.getAnnotationsFacesConfig(DefaultFacesConfigurationProvider.java:152)
at org.apache.myfaces.config.DefaultFacesConfigurationMerger.getFacesConfigData(DefaultFacesConfigurationMerger.java:91)
at org.apache.myfaces.config.FacesConfigurator.configure(FacesConfigurator.java:416)
at org.apache.myfaces.webapp.AbstractFacesInitializer.buildConfiguration(AbstractFacesInitializer.java:338)
at org.apache.myfaces.webapp.Jsp21FacesInitializer.initContainerIntegration(Jsp21FacesInitializer.java:73)
at org.apache.myfaces.webapp.AbstractFacesInitializer.initFaces(AbstractFacesInitializer.java:140)
at org.apache.myfaces.webapp.StartupServletContextListener.contextInitialized(StartupServletContextListener.java:111)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4779)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5273)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1566)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1556)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.ClassNotFoundException: org.primefaces.model.TreeNode
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1711)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1556)
... 24 more
29.10.2012. 13:03:57 org.apache.catalina.core.StandardContext startInternal
SEVERE: Error listenerStart
29.10.2012. 13:03:57 org.apache.catalina.core.StandardContext startInternal
SEVERE: Context [/EWC] startup failed due to previous errors
升级后 TreeNode 可能会出现什么问题？