大伙帮帮忙 struts的validator问题

validation.xml 内容如下<formset>
      <form    name="registerForm">
         <field    property="name"
             depends="required,minlength">
               <arg0 key="registrationForm.firstname.displayname"/>
               <arg1 name="minlength" key="${var:minlength}" resource="false"/>
                     <var>
                       <var-name>minlength</var-name>
                       <var-value>5</var-value>
                     </var>
         </field>
         <field    property="email"
             depends="required,email"
                   page="2">
               <arg0 key="registrationForm.email.displayname"/>
           </field>
         </form>
         
      
   </formset>属性文件加入了相应的KEY,struts文件也做了相当的配置.当执行form的validate方法时就报以下错误.
2007/05/10 11:09:49 org.apache.struts.validator.ValidatorForm validate
致命的: org.apache.struts.validator.FieldChecks.validateRequired(java.lang.Object, org.apache.commons.validator.ValidatorAction, org.apache.commons.validator.Field, org.apache.struts.action.ActionErrors, javax.servlet.http.HttpServletRequest)
org.apache.commons.validator.ValidatorException: org.apache.struts.validator.FieldChecks.validateRequired(java.lang.Object, org.apache.commons.validator.ValidatorAction, org.apache.commons.validator.Field, org.apache.struts.action.ActionErrors, javax.servlet.http.HttpServletRequest)
at org.apache.commons.validator.ValidatorAction.loadValidationMethod(ValidatorAction.java:627)
at org.apache.commons.validator.ValidatorAction.executeValidationMethod(ValidatorAction.java:557)
at org.apache.commons.validator.Field.validateForRule(Field.java:827)
at org.apache.commons.validator.Field.validate(Field.java:906)
at org.apache.commons.validator.Form.validate(Form.java:174)
at org.apache.commons.validator.Validator.validate(Validator.java:367)
at org.apache.struts.validator.ValidatorForm.validate(ValidatorForm.java:110)
at org.apache.struts.action.RequestProcessor.processValidate(RequestProcessor.java:928)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:204)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:595)