web.xml配备参数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:
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.