* @param registrar Registrar.
*/
private void registerWebXml(final PsiReferenceRegistrar registrar) {
registrar.registerReferenceProvider(
xmlTag().withLocalName("param-name").and(WEB_XML_STRUTS_FILTER),
new WebXmlStrutsConstantNameReferenceProvider());
registrar.registerReferenceProvider(
xmlTag().withLocalName("param-value").and(WEB_XML_STRUTS_FILTER),
new WebXmlStrutsConstantValueReferenceProvider());
}