struts怪异问题

web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app>

<display-name>Struts Hibernate Spring</display-name>

<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>

<servlet>
<servlet-name>action</servlet-name>
<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/struts-config.xml</param-value>
</init-param>
</servlet>

<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping> <taglib>   
<taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>   
<taglib-location>/WEB-INF/struts-bean.tld</taglib-location>   
</taglib> <taglib>
<taglib-uri>/WEB-INF/struts-html.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-html.tld</taglib-location>
</taglib> <taglib>
<taglib-uri>/WEB-INF/struts-logic.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-logic.tld</taglib-location>
</taglib> <taglib>
<taglib-uri>/WEB-INF/struts-template.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-template.tld</taglib-location>
</taglib></web-app>struts-config.xml
<?xml version="1.0" encoding="UTF-8"?>
<struts-config> <action-mappings>

<action path="/HelloWorld"
type="hello.HelloAction"
name="HelloForm"
scope="request"
input="index.jsp">
<forward name="SayHello" path="index.jsp"/>
</action>

</action-mappings>

<form-beans>
<form-bean name="HelloForm" type="hello.HelloForm"/>
</form-beans>

<message-resources parameter="hello.app"/>

</struts-config>HelloAction.java
package hello;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;public class HelloAction extends Action { public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {

String hf = (String)((HelloForm)form).getUserName();

request.setAttribute("username", hf);

return mapping.findForward("SayHello");
}
}HelloForm.java
package hello;import javax.servlet.http.HttpServletRequest;import org.apache.struts.action.ActionErrors;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionMessage;public class HelloForm extends ActionForm { /**
 * 
 */
private static final long serialVersionUID = 1L; private String userName = null; public String getUserName() {
return userName;
} public void setUserName(String userName) {
this.userName = userName;
}

public void reset(ActionMapping mapping, HttpServletRequest request) {
this.userName = null;
}

public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) {

ActionErrors msg  = new ActionErrors();

if (userName == null) {
msg.add("username", new ActionMessage("index.jsp.no.username.error"));
}

return msg;

}
}
index.jsp
<%@ page language="java" contentType="text/html; charset=windows-31j"
    pageEncoding="windows-31j"%>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html:html locale="true">

<head>
<title><bean:message key="index.jsp.title"/></title>
<html:base/>
</head>

<body>
<p>
<bean:message key="index.jsp.header"/>
</p>
<br>
<p>
<html:errors/>
</p>
<p>
<logic:present name="username" scope="request">
<bean:message key="index.jsp.say.hello"/>
<bean:write name="username"/>
</logic:present>
</p>
<p>
<html:form action="/Welcome.do" focus="userName">
<bean:message key="index.jsp.page.username"/>
<html:text property="userName"></html:text><br>
<html:submit></html:submit>
<html:reset></html:reset>
</html:form>
</p>
</body>

</html:html>控制台报错
致命的: サーブレット jsp のServlet.service()が例外を投げました
java.lang.NullPointerException
at org.apache.struts.taglib.TagUtils.retrieveMessageResources(TagUtils.java:1219)
at org.apache.struts.taglib.TagUtils.message(TagUtils.java:1082)
at org.apache.struts.taglib.bean.MessageTag.doStartTag(MessageTag.java:226)
at org.apache.jsp.index_jsp._jspx_meth_bean_message_0(org.apache.jsp.index_jsp:180)
at org.apache.jsp.index_jsp._jspx_meth_html_html_0(org.apache.jsp.index_jsp:123)
at org.apache.jsp.index_jsp._jspService(org.apache.jsp.index_jsp:93)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
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)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:744)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Unknown Source)