一个请求被多个过滤器拦截，实现相同的过滤任务，为什么只被过滤一次

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>

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

<filter>
<filter-name>fl</filter-name>
<filter-class>org.filter.FirstFilter</filter-class>

<init-param>
<param-name>name</param-name>
<param-value>jim</param-value>
</init-param>
</filter>



<filter-mapping>
<filter-name>fl</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>


<filter-mapping>
<filter-name>fl</filter-name>
<url-pattern>/index.jsp</url-pattern>
</filter-mapping>
</web-app>


FirstFilter.java[

package org.filter;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspWriter;

public class FirstFilter implements Filter {

private FilterConfig fil;
private String parameter;
private int i;
public void destroy() {
this.fil = null;

}

public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
System.out.println("进入了拦截器之中");
System.out.println("parameter===="+parameter);
HttpServletRequest req = (HttpServletRequest)arg0;
Enumeration<String> enum2 = req.getHeaderNames();
while(enum2.hasMoreElements()){
String headerName = enum2.nextElement();
String headerValue =req.getHeader(headerName);
System.out.println("headerName=============="+headerName);
System.out.println("headerValue=============="+headerValue);
}
arg1.setContentType("text/html;charaset=GB2312");
PrintWriter out = arg1.getWriter();
out.write("您的IP地址是==="+req.getRemoteHost());

try {
arg2.doFilter(arg0, arg1);
System.out.println("执行了a========"+i);
System.out.println(req.getRequestURI());
i++;


} catch (Exception e) {
e.printStackTrace();
}


out.write("getlocalPort===="+req.getLocalPort());

}

public void init(FilterConfig arg0) throws ServletException {
this.fil = arg0;
parameter = arg0.getInitParameter("name");
System.out.println("parameter===="+parameter);
i=1;
}

}


index.jsp[

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
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%>">

<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>

<body>
aa
</body>
</html>

运行结果
??IP???===0:0:0:0:0:0:0:1 aa getlocalPort====8888


index.jsp理论上应该是被拦截两次啊
为什么只被拦截了一次