what does load-on-startup do in web.xml ?

1. <servlet>  
2.         <servlet-name>action</servlet-name>  
3.         <servlet-class>  
4.             org.apache.struts.action.ActionServlet  
5.         </servlet-class>  
6.         <init-param>  
7.             <param-name>config</param-name>  
8.             <param-value>/WEB-INF/struts-config.xml</param-value>  
9.         </init-param>  
10.         <load-on-startup>1</load-on-startup>  
11.     </servlet>  

 Servlets are not loaded until they are first accessed by a request. This may result in a slow access time for the first user. The load-on-startup tag allows you to force the container to load and initialize the servlet at startup. 

The load-on-startup element indicates that this servlet should be loaded (instantiated and have its init() called) on the startup of the web application. The optional contents of these element must be an integer indicating the order in which the servlet should be loaded. If the value is a negative integer, or the element is not present, the container is free to load the servlet whenever it chooses. If the value is a positive 128 integer or 0, the container must load and initialize the servlet as the application is deployed. The container must guarantee that servlets marked with lower integers are loaded before servlets marked with higher integers. The container may choose the order of loading of servlets with the same load-on-start-up value.