web.xml的配置中<context-param>配置作用：

1.啟動一個WEB專案的時候,容器(如:Tomcat)會去讀它的配置檔案web.xml.讀兩個節點: <listener></listener> 和 <context-param></context-param>

<!-- 載入spring的配置檔案 -->
<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/applicationContext.xml,/WEB-INF/action-servlet.xml,/WEB-INF/jason-servlet.xml</param-value>
</context-param>
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
 

public class SysListener extends HttpServlet implements ServletContextListener {
   private static final Log logger = LogFactory.getLog(SysListener.class);
   //用於在容器關閉時,操作
   public void contextDestroyed(ServletContextEvent sce) {   
   }
   //用於在容器開啟時,操作
   public void contextInitialized(ServletContextEvent sce) {
       String rootpath = sce.getServletContext().getRealPath("/");
       System.out.println("-------------rootPath:"+rootpath);   
       if (rootpath != null) {
          rootpath = rootpath.replaceAll("\\\\", "/");
       } else {
          rootpath = "/";
       }
       if (!rootpath.endsWith("/")) {
            rootpath = rootpath + "/";
       }
       Constant.ROOTPATH = rootpath;
       logger.info("Application Run Path:" + rootpath);
       String urlrewrtie = sce.getServletContext().getInitParameter("urlrewrite");
       boolean burlrewrtie = false;
       if (urlrewrtie != null) {
           burlrewrtie = Boolean.parseBoolean(urlrewrtie);
       }
       Constant.USE_URL_REWRITE = burlrewrtie;
       logger.info("Use Urlrewrite:" + burlrewrtie);
       其它略之....    
   }

}

/*最終輸出
   -------------rootPath:D:\tomcat_bbs\webapps\BBSCS_8_0_3\
   2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]Application Run Path:D:/tomcat_bbs/webapps/BBSCS_8_0
   2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]Use Urlrewrite:true
   2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]Use Cluster:false
   2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]SERVLET MAPPING:*.bbscs
   2009-06-09 21:51:46,573 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]Post Storage Mode:1
   */

1. <context-param>
2.            <param-name>context/param</param-name>
3.            <param-value>avalible during application</param-value>
4. </context-param>

1. <servlet>
2.     <servlet-name>MainServlet</servlet-name>
3.     <servlet-class>com.wes.controller.MainServlet</servlet-class>
4.     <init-param>
5.        <param-name>param1</param-name>
6.        <param-value>avalible in servlet init()</param-value>
7.     </init-param>
8.     <load-on-startup>0</load-on-startup>
9. </servlet>

1. package com.wes.controller;import javax.servlet.ServletException;  
2. import javax.servlet.http.HttpServlet;publicclass MainServlet extends HttpServlet {   
3. public MainServlet() {  
4.         super();  
5.     }  
6.     publicvoid init() throws ServletException ...{  
7.          System.out.println("下面的兩個引數param1是在servlet中存放的");  
8.          System.out.println(this.getInitParameter("param1"));  
9.          System.out.println("下面的引數是存放在servletcontext中的");  
10.          System.out.println(getServletContext().getInitParameter("context/param"));  
11.       }  
12. }