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web.xml的初始化参数

时间:2014-11-17 15:24:33      阅读:235      评论:0      收藏:0      [点我收藏+]

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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----------

---------------------------------------------------------------------------------------------------

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

 

---------------------------------------------------------------------------------------------------------------------------------------

 

 

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

 

 

web.xml的初始化参数

标签:des   style   blog   http   io   color   ar   sp   java   

原文地址:http://www.cnblogs.com/kzhan/p/4103441.html

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