public static String getResourceURL(FacesContext context, String value) {
        if (LangUtils.isBlank(value)) {
            return Constants.EMPTY_STRING;
        }
        else if (value.contains(ResourceHandler.RESOURCE_IDENTIFIER)) {
            return value;
        }
        else {
            String url = context.getApplication().getViewHandler().getResourceURL(context, value);

            return context.getExternalContext().encodeResourceURL(url);
        }
    }
Used to extract resource name (e.g. "#{resource['picture.png'}")
primefaces/src/main/java/org/primefaces/util/ResourceUtils.java