标签：des style blog http io color ar sp java
web.xml的初始化参数
---------首先声明，这里所介绍的是web中context-param,init-param参数的初始化配置----------
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一、初始化参数
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>cn.jbit.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 cn.jbit.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("下面的参数是存放在servletcontext中的"); System.out.println(getServletContext().getInitParameter("context/param")); System.out.println("下面的两个参数param1是在servlet中存放的"); System.out.println(this.getInitParameter("param1")); } }
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
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二、初始化参数获
<!--application 模式-->
<context-param> <param-name>count</param-name> <param-value>1200</param-value> </context-param>
<!--servlet-->
<servlet> <description>loginServlet</description> <display-name>loginServlet</display-name> <servlet-name>loginServlet</servlet-name> <servlet-class>loginServlet</servlet-class>
<!--servlet 初始化时 init()-->
<init-param> <description>系统初始化数</description> <param-name>num</param-name> <param-value>100</param-value> </init-param>
</servlet>
<servlet-mapping> <servlet-name>loginServlet</servlet-name> <url-pattern>/loginServlet</url-pattern> </servlet-mapping>
在servlet中获取参数的方法以及异同:
response.setCharacterEncoding("gb2312"); System.out.println("getServletContext()："+getServletContext()); ServletContext context=getServletConfig().getServletContext(); String num=context.getInitParameter("num");// <init-param> 获取不到值 String count=context.getInitParameter("count");//<context-param> 获取到值 System.out.println("num："+num);//null System.out.println("count："+count);//1200 System.out.println("num："+getServletConfig().getInitParameter("num"));//100获取到值 System.out.println("count："+getServletConfig().getInitParameter("count"));//null获取不到值
标签：des style blog http io color ar sp java
原文地址：http://www.cnblogs.com/kzhan/p/4103441.html
