本文转自:http://yangran900529.blog.163.com/blog/static/2075201002012429083980/



web.xml里面可以定义两种参数:
(1)application范围内的参数,存放在servletcontext中,在web.xml中配置如下:

 <context-param>
           <param-name>context/paramparam-name>
           <param-value>avalible during applicationparam-value>
  context-param>

(2)servlet范围内的参数,只能在servlet的init()方法中取得,在web.xml中配置如下:

 <servlet>
    <servlet-name>MainServletservlet-name>
    <servlet-class>com.wes.controller.MainServletservlet-class>
    <init-param>
       <param-name>param1param-name>
       <param-value>avalible in servlet init()param-value>
    init-param>
    <load-on-startup>0load-on-startup>
 servlet>

在servlet中可以通过代码分别取用:

package com.wes.controller;

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

public class MainServlet extends HttpServlet {

    public MainServlet() {
        super();
     }
    public void init() throws ServletException {
         System.out.println("下面的两个参数param1是在servlet中存放的");
         System.out.println(this.getInitParameter("param1"));
         System.out.println("下面的参数是存放在servletcontext中的");
         System.out.println(getServletContext().getInitParameter("context/param"));
      }
}

第一种参数在servlet里面可以通过getServletContext().getInitParameter("context/param")得到
第二种参数只能在servlet的init()方法中通过this.getInitParameter("param1")取得

理解能力有些问题,才弄明白他们之间的关系。