servlet中配置文件web.xml中的参数context-param和init-param区别

servlet中配置文件web.xml中的参数context-param和init-param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：
Java代码
   
<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：
Java代码
<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：
Java代码
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
第二种参数只能在servlet的init()方法中通过this.getInitParameter("param1")取得