HTTP Status 404 web.xml有关问题

HTTP Status 404 web.xml问题
想学习jsp+struts2,可是在学教程时写第一个实例就提示HTTP Status 404 错误了,代码如下:
web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
xmlns="http://java.sun.com/xml/ns/javaee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <display-name></display-name>
   <filter-mapping>
    <filter-name>struts2</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>






struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<!-- 改变url现实的后缀,默认是action -->
    <constant name="struts.action.extension" value="xhtml" />
    
<package name="struts2login" extends="struts-default">
    <!-- 这里的Class是由Spring里面制定的ID,如果单独用struts2,则这里是包名+类名 -->
<action name="UserLogin" class="com.greatwqs.action.PersonAction">
<result name="success" >/login_s.jsp</result>
<result name="input">/login.jsp</result>
</action>
</package>
</struts>


login.jsp

<%@ page pageEncoding="utf-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>    
    <title>Struts2 Person Login Test</title>
  </head>
  
  <body>
    <s:form action="UserLogin">
     <s:textfield name="per.username" label="username"></s:textfield>
     <s:password name="per.password" label="password"></s:password>
     <s:submit></s:submit>
    </s:form>
  </body> 
</html>


login_s.jsp

<%@ page language="java"  pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
String username = (String)session.getAttribute("user");
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    <title>Struts2 Person Login Result</title>
  </head>
  
  <body>
    Hi:<br>
    <%=username%><br>
    Welcome... <br>
  </body>
</html>


PersonAction.java

package com.greatwqs.action;

import java.util.Map;

import com.greatwqs.dao.PersonDao;
import com.greatwqs.entity.Person;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
/***
 * 
 * @author greatwqs.iteye.com
 * @data 2011-12-01
 */
public class PersonAction extends ActionSupport {

private Person per;

private static final long serialVersionUID = 1L;

public String execute() throws Exception {
PersonDao dao = new PersonDao();
boolean flag = dao.isPersonCanLogin(per.getUsername(), per.getPassword());
if(flag){
Map session=(Map)ActionContext.getContext().get(ActionContext.SESSION);
session.put("user", per.getUsername());
return SUCCESS;
} else {
return INPUT;
}
}

public Person getPer() {
return per;
}

public void setPer(Person per) {
this.per = per;
}
}


PersonDao.java

package com.greatwqs.dao;
/***
 * 
 * @author greatwqs.iteye.com
 * @data 2011-12-01
 */
public class PersonDao {

/***
 * 根据用户名和密码,判断用户是否能登陆!
 * @param username
 * @param password
 * @return
 */
public boolean isPersonCanLogin(String username, String password) {