struts2中FreeMarker template error!异常

在看struts2.1权威指南时，看书上的代码写的，但是出现了以下的错误，书上有，但是我改过来以后还是不行，不知道究竟是怎么回事了

错误如下：FreeMarker template error!

Method public java.util.List org.apache.struts2.components.Form.getValidators(java.lang.String) threw an exception when invoked on org.apache.struts2.components.Form@1bb1dd2
The problematic instruction:
----------
==> list tag.getValidators("${tagName}") as validator [on line 46, column 9 in template/xhtml/form-close-validate.ftl]
 in include "/${parameters.templateDir}/xhtml/form-close-validate.ftl" [on line 25, column 1 in template/xhtml/form-close.ftl]
----------

Java backtrace for programmers:
----------
freemarker.template.TemplateModelException: Method public java.util.List org.apache.struts2.components.Form.getValidators(java.lang.String) threw an exception when invoked on org.apache.struts2.components.Form@1bb1dd2
	at freemarker.ext.beans.SimpleMethodModel.exec(SimpleMethodModel.java:130)
	at freemarker.core.MethodCall._getAsTemplateModel(MethodCall.java:93)
	at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
	at freemarker.core.Environment.visit(Environment.java:221)
	at freemarker.core.IteratorBlock$Context.runLoop(IteratorBlock.java:167)
	at freemarker.core.Environment.visit(Environment.java:428)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:102)
	at freemarker.core.Environment.visit(Environment.java:221)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:221)
	at freemarker.core.ConditionalBlock.accept(ConditionalBlock.java:79)
	at freemarker.core.Environment.visit(Environment.java:221)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:221)
	at freemarker.core.Environment.include(Environment.java:1508)
	at freemarker.core.Include.accept(Include.java:169)
	at freemarker.core.Environment.visit(Environment.java:221)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:221)
	at freemarker.core.Environment.process(Environment.java:199)
	at freemarker.template.Template.process(Template.java:259)
	at org.apache.struts2.components.template.FreemarkerTemplateEngine.renderTemplate(FreemarkerTemplateEngine.java:157)
	at org.apache.struts2.components.UIBean.mergeTemplate(UIBean.java:559)
	at org.apache.struts2.components.UIBean.end(UIBean.java:513)
	at org.apache.struts2.views.jsp.ComponentTagSupport.doEndTag(ComponentTagSupport.java:42)
	at org.apache.jsp.regist_jsp._jspx_meth_s_005fform_005f0(regist_jsp.java:198)
	at org.apache.jsp.regist_jsp._jspService(regist_jsp.java:112)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:428)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
	at com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.buildValidatorKey(AnnotationActionValidatorManager.java:219)
	at com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.getValidators(AnnotationActionValidatorManager.java:76)
	at com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.getValidators(AnnotationActionValidatorManager.java:72)
	at org.apache.struts2.components.Form.getValidators(Form.java:265)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces

前台代码：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="/struts-tags"  prefix="s"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
	<s:head/>
  </head>
  
  <body>
  	<s:fielderror />
	<s:form action="regist" validate="true">
		<s:textfield label="用户名" name="name" />
		<s:password label="密码" name="pass"/>
		<s:textfield label="年龄" name="age"/>
		<s:textfield label="生日" name="birth"/>
		<s:submit label="注册"/>
	</s:form>

  </body>
</html>

请大家帮助看看究竟是怎么回事啊