In your web xml wicket is a filter not a servlet.
<filter>
<filter-name>ApplicationName</filter-name>
<filter-class>org.apache.wicket.protocol.http.WicketFilter</filter-class>
<init-param>
<param-name>applicationClassName</param-name>
<param-value>your.package.Application</param-value>
</init-param>
<init-param>
<param-name>configuration</param-name>
<param-value>deployment</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>Helloworld</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>