servlet中配置文件web.xml中的参数context-param和init-param区别

  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/param</param-name>
            <param-value>avalible during application</param-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>MainServlet</servlet-name>
    <servlet-class>com.wes.controller.MainServlet</servlet-class>
    <init-param>
       <param-name>param1</param-name>
       <param-value>avalible in servlet init()</param-value>
    </init-param>
    <load-on-startup>0</load-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