context-param和init-param區別

web.xml裏面可以定義兩種參數：
(1)application範圍內的參數，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範圍內的參數，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中可以通過代碼分別取用：

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("下面的兩個參數param1是在servlet中存放的");
         System.out.println(this.getInitParameter("param1"));
         System.out.println("下面的參數是存放在servletcontext中的");
         System.out.println(getServletContext().getInitParameter("context/param"));
      }
}

第一種參數在servlet裏面可以通過getServletContext().getInitParameter("context/param")得到
第二種參數只能在servlet的init()方法中通過this.getInitParameter("param1")取得