Web. xml File Structure understanding

Start kick: servlet, filter, listener
1. Start with the servlet node, including Servlet-name, Servlet-class, Init-param (Param-name, param-value), Load-on-startup
2.servlet corresponding servlet-mapping nodes, including Servlet-name, Url-pattern
3.filter, including Filter-name, Filter-class, Init-param (Param-name, Param-value)
4.filter corresponding filter-mapping nodes, including Filter-name, Url-pattern
5.listener listener nodes, including Listener-class
6.context-param, context parameters, including Param-name, Param-value
7.welcome-file-list node, first page configuration list welcome-file
8.session-config node, configuring session-config timeout length