本文是根据tomcat平台下实现而做，文件目录为：

下面开始修改web.xml令filesevelet生效/*

       <?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
    "">

<web-app>
  <display-name>Welcome to Tomcat</display-name>
  <description>
     Welcome to Tomcat
  </description>

<!-- JSPC servlet mappings start -->

    <servlet>
        <servlet-name>org.apache.jsp.index_jsp</servlet-name>
        <servlet-class>org.apache.jsp.index_jsp</servlet-class>
    </servlet>
    
        <servlet-mapping>
        <servlet-name>org.apache.jsp.index_jsp</servlet-name>
        <url-pattern>/index.jsp</url-pattern>
    </servlet-mapping>
        <servlet>
        <servlet-name>FileServlet</servlet-name>
        <servlet-class>com.FileServlet</servlet-class>
    </servlet>   
    <servlet-mapping>
        <servlet-name>FileServlet</servlet-name>
        <url-pattern>/servlet/FileServlet</url-pattern>
    </servlet-mapping>
<!-- JSPC servlet mappings end -->

</web-app> 

在浏览器中输入：

OK，出现以下面面：