web.xml配备参数context-param和init-param的区别(转)

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

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：

1. <context-param>??
2. ???????????<param-name>context/param</param-name>??
3. ???????????<param-value>avalible during application</param-value>??
4. </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：

1. <servlet>??
2. ????<servlet-name>MainServlet</servlet-name>??
3. ????<servlet-class>com.wes.controller.MainServlet</servlet-class>??
4. ????<init-param>??
5. ???????<param-name>param1</param-name>??
6. ???????<param-value>avalible in servlet init()</param-value>??
7. ????</init-param>??
8. ????<load-on-startup>0</load-on-startup>??
9. </servlet>??

在servlet中可以通过代码分别取用：

1. package?com.wes.controller; ??
2. ??
3. import?javax.servlet.ServletException; ??
4. import?javax.servlet.http.HttpServlet; ??
5. ??
6. public?class?MainServlet?extends?HttpServlet{ ??
7. ??
8. ????public?MainServlet(){ ??
9. ????????super(); ??
10. ??????} ??
11. ????public?void?init()?throws?ServletException ...{ ??
12. ??????????System.out.println("下面的两个参数param1是在servlet中存放的"); ??
13. ??????????System.out.println(this.getInitParameter("param1")); ??
14. ??????????System.out.println("下面的参数是存放在servletcontext中的"); ??
15. ??????????System.out.println(getServletContext().getInitParameter("context/param")); ??
16. ???????} ??
17. }??

?
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