public static List<String> getFilterNames( Document webXml )
    {
        return getNames( "filter", webXml );
    }
Retrieves the names of all filters from a web.xml document.

Returns a list that contains 'message' from this web.xml document:
&lt;filter&gt;
  &lt;filter-name&gt;message&lt;/filter-name&gt;
  &lt;filter-class&gt;com.acme.filter.MessageFilter&lt;/filter-class&gt;
&lt;/filter&gt;

@param webXml web.xml document, parsed as XML (cannot be null)
@return The name of the filter class, or null when no such class was defined.
xmppserver/src/main/java/org/jivesoftware/util/WebXmlUtils.java