我在用Validator验证框架时碰到发生以下错误：
[ERROR] DynaValidatorForm - 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)> 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.DynaValidatorForm.validate(DynaValidatorForm.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.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)