web.xml配置参数context-param和init-param的区别

web.xml配置参数context-param和init-param的区别

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>

<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>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>

<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中可以通过代码分别取用：

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("下面的两个参数param1是在servlet中存放的");
          System.out.println(this.getInitParameter("param1"));
          System.out.println("下面的参数是存放在servletcontext中的");
          System.out.println(getServletContext().getInitParameter("context/param"));
       }
}

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("下面的两个参数param1是在servlet中存放的");    
          System.out.println(this.getInitParameter("param1"));    
          System.out.println("下面的参数是存放在servletcontext中的");    
          System.out.println(getServletContext().getInitParameter("context/param"));    
       }    
}

 第一种参数在servlet里面可以通过getServletContext().getInitParameter("context/param")得到

在JSP中可以用config.getServletContext().getInitParameter("context/param")得到

或者this.getServletContext().getInitParameter("context/param")

第二种参数只能在servlet的init()方法中通过this.getInitParameter("param1")取得.