防止列出文件目录

<servlet>
  <servlet-name>default</servlet-name>
  <servlet-class>com.sun.enterprise.web.servlets.DefaultServlet</servlet-class>
- <init-param>
  <param-name>debug</param-name>
  <param-value>0</param-value>
  </init-param>
- <init-param>
  <param-name>listings</param-name>
  <param-value>false</param-value>
  </init-param>
  <load-on-startup>1</load-on-startup>
  </servlet>