Try to change ur web.xml to look like this
<servlet>
<servlet-name>xyz</servlet-name>
<servlet-class>xyzServlet</servlet-class>
<init-param>
<param-name>properties</param-name>
<param-value>/WEB-INF/conf/helpdesk.properties</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
put ur properties file at web-inf\conf\ directory.
Later in ur servlet u can read the init parameter like this.
String filename = getServletContext().getInitParameter("properties");
Hope this hlep