<context-param>與<init-param>的區別與作用
web.xml的配置中<context-param>配置作用
1. 啓動一個WEB項目的時候,容器(如:Tomcat)會去讀它的配置文件web.xml.讀兩個節點: <listener></listener> 和 <context-param></context-param>
context-param的值 = ServletContext.getInitParameter("context-param的鍵");
換句話說,這個時候,你對<context-param>中的鍵值做的操作,將在你的WEB項目完全啓動之前被執行.
那麼這裏就可以在<context-param>中設置數據庫的連接方式,在監聽類中初始化數據庫的連接.
<!-- 加載spring的配置文件 -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml,/WEB-INF/action-servlet.xml,/WEB-
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<param-name>urlrewrite</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<param-name>cluster</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<param-name>servletmapping</param-name>
<param-value>*.bbscs</param-value>
</context-param>
<context-param>
<param-name>poststoragemode</param-name>
<param-value>1</param-value>
</context-param>
<listener>
<listener-class>com.laoer.bbscs.web.servlet.SysListener</listener-class>
</listener>
}
String rootpath = sce.getServletContext().getRealPath("/");
System.out.println("-------------rootPath:"+rootpath);
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]
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
2009-06-09 21:51:46,573 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
*/
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>
<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>
package com.wes.controller;
import javax.servlet.http.HttpServlet;
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"));
}
}
第二種參數只能在servlet的init()方法中通過this.getInitParameter("param1")取得.