WEB应用中的普通Java程序如何读取资源文件

 package cn.itcast;

 import java.io.IOException;
 import java.io.PrintWriter;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 //servlet调用其他程序，在其他程序中何如读取资源文件（通过类装载器）
 public class ServletDemo3 extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         UserDao dao = new UserDao();
         dao.find();

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

     }

 }

 package cn.itcast;

 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Properties;

 //如果读取资源文件的程序不是servlet的话，就只能通过类装载器去读
 public class UserDao {

     private static Properties dbconfig = new Properties();
     static {
         InputStream in = UserDao.class.getClassLoader().getResourceAsStream(
                 "db.properties");
         try {
             dbconfig.load(in);
         } catch (IOException e) {
             throw new ExceptionInInitializerError(e);
         }
     }
     //以下代码虽然可以读取资源文件数据，但是无法获取更新后的数据
     public void update() throws IOException {

         System.out.println(dbconfig.getProperty("url"));
     }

     //通过类装载的方式得到资源文件位置，再通过传统方式读取资源文件的数据，这样可以读取更新后的数据
     public void find() throws IOException {
         String path = UserDao.class.getClassLoader().getResource("db.properties").getPath();
         FileInputStream in = new FileInputStream(path);

         Properties dbconfig = new Properties();
         dbconfig.load(in);

         System.out.println(dbconfig.getProperty("url"));

     }

 }

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app version="2.4"
     xmlns="http://java.sun.com/xml/ns/j2ee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
     http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

 <servlet>
     <servlet-name>ServletDemo1</servlet-name>
     <servlet-class>cn.itcast.ServletDemo1</servlet-class>
 </servlet>
   <servlet>
     <servlet-name>ServletDemo3</servlet-name>
     <servlet-class>cn.itcast.ServletDemo3</servlet-class>
   </servlet>

 <servlet-mapping>
     <servlet-name>ServletDemo1</servlet-name>
     <url-pattern>/ServletDemo1</url-pattern>
 </servlet-mapping>
   <servlet-mapping>
     <servlet-name>ServletDemo3</servlet-name>
     <url-pattern>/servlet/ServletDemo3</url-pattern>
   </servlet-mapping>

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