@SuppressWarnings("unchecked")
    private <T, K> List<T> requireJsonArray(String keyName, JsonObject json, Class<K> klazz) {
        // Contains key.
        Arguments.require(json.containsKey(keyName),
                String.format("Must provide array of %s objects for key '%s'", StringUtils.capitalize(keyName), keyName));
        // Is of type array.
        Arguments.require(json.getValue(keyName) instanceof JsonArray,
                String.format("'%s' must be a Json array", keyName));
        // Transform into List<T>.
        return Json.decodeValue(json.getJsonArray(keyName).encode(), List.class, klazz);
    }
Excepute the fetcher and load the resources.
gateway/engine/vertx-polling/src/main/java/io/apiman/gateway/engine/vertx/polling/PolicyConfigLoader.java