引起的原因是我在其他包内定义了静态的方法，在Struts2里的Action中调用，结果发生以下错误。
我以为是Action不能调用其他静态方法呢，可是不是。
根据意思，是反射的错误，后面的错误更离谱，不能加载类。
通过网络，怀疑是服务器环境问题！我将Tomcat的JDK配置为了JDK6.0后错误解决。
更有时我们还要将项目的编辑级别设置为6.0。

java.lang.reflect.InvocationTargetException
 sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 java.lang.reflect.Method.invoke(Unknown Source)
 com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:441)
 com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:280)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:243)
 com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:165)
 com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:252)
 org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
 com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
 com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
 com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:179)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:306)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:130)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138)
 com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:165)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:179)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176)
 com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
 org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
 org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:488)
 org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
 org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
 org.hawk.fileter.PagerFilter.doFilter(PagerFilter.java:47)

网络上许多人都发生了这样的错误，有的解决了！可是，究竟是为什么，还是有待考究！